NATIONAL CANNERS ASSOCIATION
                RESEARCH LABORATORY—Bulletin No. 21L.
                        W. D. BIGELOW, Director


                            Tomato Products

                           Pulp, Ketchup and
                              Chili Sauce

                                  BY
                   W. D. BIGELOW and A. E. STEVENSON

                            [Illustration]

                           WASHINGTON, D. C.
                             AUGUST, 1923




CONTENTS


                                 Pulp

                                                                  PAGE
  Introduction                                                       5
  Sanitary control of tomato pulp factories                          6
  Quality of product                                                 7
  Discarding tomato juice                                            8
  Composition of tomato pulp                                        10
                 Whole tomato pulp                                  10
                 Trimming stock pulp                                12
  Methods of analysis                                               12
             Microscopic examination                                13
             Determination of total solids                          19
             Determination of insoluble solids                      32
             Determination of sugar                                 32
             Determination of acidity                               33
             Determination of salt                                  33
             Determination of specific gravity                      33
  Importance of accuracy in the determination of specific gravity   50
  Evaporation to definite volume of concentrated pulp               52

                               Ketchup

  Methods of manufacture                                            62
  Factory control of the composition of Ketchup                     63

                              Chili Sauce

  Methods of manufacture                                            72




TABLES


  Table 1, Composition of pulp and of the liquor separated from it   9
  Table 2, Composition of whole tomato pulps                        21
  Table 3, Composition of trimming stock pulps                      22
  Table 4, Comparison of methods for the determination and
      calculation of solids in whole tomato pulp                    23
  Table 5, Tomato pulp and filtered liquor                          24
  Table 6, Corrections for specific gravity of hot pulp             43
  Table 7, Comparisons of methods for determining specific gravity  45
  Table 8, Corrections for specific gravity and Brix readings at
      different temperatures                                        55
  Table 9, Equivalent volumes of pulp of different degrees of
      concentration                                                 56
  Table 10, Specific gravity and solids of tomato pulp              59
  Table 11, Manufacture of Ketchup. Quantity of constituents to
      be added to 800 gallons of boiling, partly concentrated pulp  65
  Table 12, Solids in Ketchup obtained by drying in vacuum at
      70° C. and by Abbé refractometer from Geerlig’s table         68
  Table 13, Refractive index and per cent solids in Tomato Ketchup  69
  Table 14, Corrections for temperature to be used with Table 13    70




ILLUSTRATIONS


  Fig. 1. Small specific gravity flask                              36
  Fig. 2. Large specific gravity flask                              36
  Fig. 3. Special head and flask receptacles for Babcock milk
      tester                                                        37
  Fig. 4. Weight and specific gravity of tomato pulp                39
  Fig. 5. Specific gravity cup for hot pulp                         44




TOMATO PULP


INTRODUCTION

Tomato pulp is the fleshy portion of the tomato separated from
skins, cores and seeds by means of a fine mesh screen and suitably
concentrated by evaporation.

During recent years great improvements have been made in the
manufacture of tomato pulp and in the quality and appearance of the
product. The care exercised in the selection of the raw material and in
all steps of the manufacture of tomato pulp has been greatly increased.
This is equally true of pulp marketed in small cans to be used as soup
stock in private homes and of the pulp sold in larger containers for
the manufacture of soup and ketchup. The large buyers of pulp have
determined the grade or quality which gives them the best results in
the manufacture of other products and the degree of concentration
which they can use most economically. It is now customary, therefore,
for large sales of pulp to be made on specifications, and it is
impracticable to comply with such specifications without carefully
controlling the manufacture of the product. The raw material must be so
selected and the manufacturing operations so controlled that the color
and flavor of the finished product is conserved. This is discussed
briefly on page 7.

If he desires to sell under specification, the manufacturer must comply
with his contract with respect to specific gravity, and he cannot
greatly exceed the specific gravity specified without substantial
sacrifice in cost of manufacture. It is therefore economical to
determine the specific gravity of the product as accurately as
practicable (see p. 51) and also to adopt methods of manufacture
that will control as closely as possible the specific gravity of the
finished product.

Beginning on page 33, methods are given for the determination of
specific gravity under various conditions of manufacture and sale,
and on page 50 is given the method for the determination of specific
gravity of the cyclone juice or partly concentrated pulp which this
laboratory has suggested as an aid to determining the volume to which
the product should be evaporated to secure the desired specific
gravity. This method has been used by a number of pulp manufacturers
and found to be relatively convenient and practicable. It might be
used to better advantage and to considerably greater profit if more
help were employed—and some times more competent help—in determining
specific gravity and controlling the point at which evaporation should
stop.

The importance and economy of accuracy in the determination of specific
gravity is not fully appreciated by all, though some of the larger
manufacturers are now giving much attention to that subject. This
matter is discussed on page 50.

There is included in the bulletin beginning on page =13= a detailed
description of the Howard method for the microscopic examination
of tomato products, and following that a detailed statement of the
chemical and physical methods employed in this laboratory for their
examination. Such methods are only of value to those trained in
laboratory work. They are included here because the laboratory receives
many requests for these methods from chemists employed by manufacturers
of pulp. Men who are employed only for the tomato season find special
need for such information.

Our correspondence brings many inquiries regarding the percentage of
solids in pulp of different specific gravities, and also regarding the
relative values of pulp of different specific gravities. In Table 10
(p. 59) there is given in parallel columns the specific gravities of
pulp of different degrees of concentration and corresponding percentage
of solids, and it is a simple matter to calculate the volume which the
same pulp would make if concentrated to any other specific gravity.
This calculation is explained on page =54=—in discussing the point
at which to stop evaporation to secure pulp of any desired specific
gravity.

This bulletin supersedes Bulletins 3 and 7, and also contains material
which has appeared in several trade-paper articles prepared in this
laboratory. These articles are extensively quoted and some of them
are printed almost in full. Dr. F. F. Fitzgerald was the co-author of
most of these publications and did much of the work on which they were
based. He is therefore entitled to a substantial share of the credit
for the material in this bulletin.


SANITARY CONTROL OF TOMATO PULP FACTORIES

The manufacture of tomato pulp requires careful supervision from
beginning to end. The raw product must be carefully selected, and all
possible steps should be taken to induce growers to discard rotting
tomatoes in the field and to expedite the movement of the raw product
from field to factory. Tomatoes must be carefully washed and sorted. It
is only practicable to accomplish the latter by means of some type of
sorting belt. Sorters should not attempt to trim. Their full attention
should be given to the tomatoes passing by them. The sorter may place
the tomatoes requiring trimming in a separate receptacle in order that
they may be carried to a table not provided with a moving belt and
handled by special trimmers. Conveyors, receptacles and machines must
be constructed and installed with a view to convenience in cleaning.
Care must be taken to expedite the manufacture of the product in every
way possible in order to give no opportunity for bacterial growth
during the process of manufacture.

The brief comments given above are offered by way of reminder.
This important subject is not further discussed because it has
been adequately treated by Mr. B. J. Howard of the U. S. Bureau of
Chemistry in bulletins which are readily available. These bulletins
are designated as Bulletins 569 and 581, respectively, of the United
States Department of Agriculture. They may be secured by requesting
them of the Superintendent of Documents, Government Printing Office,
this city, and enclosing five cents in coin for each copy desired. All
manufacturers of tomato pulp will do well to study these bulletins and
have them studied by their responsible employees.


QUALITY OF PRODUCT

There is a growing tendency to give increased attention to the quality
of tomato pulp. The tomatoes should be ripe and well colored. Green
tomatoes or tomatoes with green portions not only do not have the
requisite amount of red coloring matter but they contain material
which masks and dulls the color of fully ripe tomatoes. There is a
difference of opinion among successful manufacturers of pulp regarding
the relative color of pulp manufactured after hot or cold cycloning.
Some maintain that a better color is obtained by cycloning hot. Others,
apparently equally skilled and able to manufacture an equally good
product, maintain the reverse. Much depends on the control of the
cyclone—the setting of the paddles and the speed at which they are
operated.

The evaporation should be as rapid as possible. The operation of the
kettles in such a way that the pulp burns on the kettles or on the
coils damages the flavor of the product and impairs its color. The
pulp should be cooled promptly after processing, or if that is not
practicable should be stacked loosely so that the cans will have ample
ventilation until they are entirely cooled.

Pulp packed in five-gallon cans is rarely processed. It should,
however, be filled into the cans at a temperature of at least 180° F.
It is best to give pulp in No. 10 and smaller size cans a short process
in boiling water. With pulp filled at 180° F., ten or fifteen minutes
is a sufficient cook. Pulp filled at lower temperatures or which is
allowed to partially cool before processing requires a longer process.

In order to protect the color it is best to water cool No. 10 cans of
pulp after processing. Pulp in cans of any size should not be stacked
solid while it is still hot. The metal of the can has a bleaching
action on the pulp and this is greatly increased if the pulp is stacked
hot or stored in a hot warehouse. If stacked while excessively hot,
stack-burning may occur with consequent darkening of the pulp.

As indicated above, there is a considerable difference of opinion among
successful manufacturers of pulp regarding the details of manufacture
necessary to secure the best results. It is probable that different
conditions call for different methods of operation. At any rate, all
successful manufacturers are agreed that the color of the pulp is an
important index to its quality and greatly influences its commercial
value. The flavor of pulp is also an important criterion and is
considered by many buyers in forming an estimate of the value of pulp.
A scorched taste or a flat flavor show that the manufacture of the pulp
was not adequately controlled and impairs the commercial value of the
product.

Color and flavor commonly go together. The same manufacturing methods
which yield a product of high color are likely to give a product of
superior flavor.


DISCARDING TOMATO JUICE

It was formerly customary, and is still the practice of some
manufacturers of tomato pulp, to discard a portion of the juice of the
tomatoes. Some manufacturers, especially in the preparation of pulp
from tomato trimmings, allow the trimmings to pass over a colander
and thus separate the free juice, which is discarded. Others allow
the product of the cyclone to stand for a time in tanks and then
discard the clear juice which settles in the bottom of the tanks. Both
practices are wasteful and have generally been discontinued. Some still
adhere to one or both, however, and it was thought best to make the
matter the subject of study.

Some discard the juice because of the belief that it consists of
nothing but water and is valueless. Some are of the impression that the
juice separated from the trimming stock before straining takes on a
brown color during evaporation which would interfere with the red color
desired in the finished product, if allowed to go into the pulp. Some
recognize the value of the juice, but believe that the expense of its
evaporation would not be warranted by the increased quantity of pulp.
Some have not measured the juice discarded and greatly underestimate
its volume.

With the view of determining the approximate value of the material
discarded in this manner, a batch of material, fresh from the
cyclone, was divided into two portions, one of which was immediately
concentrated to form a pulp, and the other was allowed to stand about
20 minutes when a clear liquor had separated at the bottom. This clear
liquor was then removed and the remainder evaporated until the desired
consistency was obtained.

Samples of the finished pulps, of the raw product from which each
was prepared and of the clear liquor, separated from the second one,
were preserved by sealing in cans and processing. These samples were
numbered as follows:

  702—Product from the trough under the second cyclone, or finisher.

  703—Clear liquor, which separated at the bottom of the tank, after a
  portion of 702 was allowed to stand. This formed about one-fourth
  of the entire product of the tank.

  704—Drained residue from 703.

  705—Finished pulp obtained by concentrating 704.

  706—Finished pulp obtained by concentrating 702.

These samples were examined with the results given below.


TABLE 1.—_Composition of Pulp and of the Liquor Separated from It_

===================================================================
Sample | Total  |Insoluble|  Ash   | Sugar  |  Acid  | Undetermined
Number | Solids |  Solids |        | (as    |  (as   | Organic
       |        |         |        | Invert)| Citric)| Matter
-------+--------+---------+--------+--------+--------+-------------
       | _Per   |   _Per  |  _Per  |  _Per  |  _Per  | _Per Cent_
       | Cent_  |   Cent_ |  Cent_ |  Cent_ |  Cent_ |
  702  |  4.38  |   0.40  |  0.34  |   2.27 |   0.29 |   0.87
  703  |  3.84  |   0.10  |  0.38  |   2.32 |   0.29 |   0.75
  704  |  4.47  |   0.50  |  0.38  |   2.31 |   0.31 |   0.77
  705  |  9.17  |   1.83  |  0.78  |   4.07 |   0.51 |   1.87
  706  |  7.85  |   0.98  |  0.69  |   3.51 |   0.46 |   2.04
-------+--------+---------+--------+--------+--------+-------------

The two products (705 and 706) were evaporated under exactly the
same conditions and to what appeared to the operator to be the same
consistency. After cooling, however, it was apparent that while the
body of the two finished products was apparently equal, the consistency
of No. 706 was superior to No. 705 in that the former was smooth and
creamy, whereas the latter had a somewhat irregular, lumpy appearance.
This difference was doubtless due to the greater content of soluble
solids in No. 706. The color of the two samples was identical.

A mixture of one part of No. 703 and three parts of No. 704 when
evaporated in the laboratory to the same consistency was identical in
every way with No. 706.

From the composition as stated in Table 1 it is apparent that
the flavor and food value of the clear juice, which is sometimes
discarded (represented in No. 703), are practically identical with the
unconcentrated pulp as it passes through the cyclone. In fact, the
only difference between the two appears to be about one-half per cent
of insoluble matter. When the product is allowed to separate, it seems
probable that this insoluble material as it rises in the mass has a
tendency to act like a filter and carry up with it a large proportion
of the bacteria and moulds present.

The scale on which the work was done did not permit of sufficiently
accurate measurement of the finished pulp to warrant the calculation
of the loss in quantity caused by discarding the juice. From the
composition of the pulps and of the raw material, however, it is
apparent that this loss is practically proportional to the percentage
of juice discarded.

It is apparent, therefore, that the evaporation of the material just
as it passes through the finisher will yield a product of the same
color, of better consistency, in considerably greater quantity, and
at practically the same proportionate expense of concentration as the
evaporation of the residue after discarding the juice in accordance
with the custom mentioned above.


COMPOSITION OF TOMATO PULP[1]


Whole Tomato Pulp

The results obtained by the examination of 33 samples of whole tomato
pulp are given in Table 2. The concentration of the samples varies
from unconcentrated pulp as it runs from the cyclone to pulps of very
heavy consistency. This table contains the data from which Tables 4 and
5 were calculated, although during the season a partial analysis was
made of a large number of other samples, and the data secured therefrom
were in all respects confirmatory of the relations calculated from
Table 2.

[1] This chapter is taken largely from an article by Bigelow and
Fitzgerald, published in the Journal of Industrial and Engineering
Chemistry, 1915, vol. 7, page 602.

In addition to the data obtained by the various determinations, Table 2
gives the relation between the results of the determinations for each
individual sample. For instance, the ratio of pulp solids to filtrate
solids (pulp solids divided by filtrate solids) varies in the different
samples from 1.091 to 1.154, and, with the exception of two samples,
it varies from 1.100 to 1.145. The average of the 33 samples was 1.12.
The relation of insoluble solids to total solids (expressed as per cent
of insoluble solids in total solids) is shown in Table 2. Considering
the variations in the methods employed by different manufacturers in
the preparation of tomato pulp, the per cent of insoluble solids in the
total solids as shown by this column is closer than we might expect,
varying in most of the samples from 11 to 14 per cent.

The per cent of sugar in the soluble solids, as shown by Table 2,
varies in most of the samples from 50 to 55 per cent. This figure
cannot be expected to be constant in different localities and in
different years.

The acid, estimated as citric, constitutes in most of the samples from
9 to 10 per cent of the soluble solids.

Of especial interest is the refractive constant of the filtered liquor,
shown in the last column of Table 2. The refractive constant of the
various samples is much more uniform than might be expected from a
product of this nature.

Table 2 is chiefly interesting as affording the data from which Tables
4 and 5 were calculated. The uniformity of the relations shown in
Table 5 is such that it is usually possible from one determination on
the filtrate and the determination of solids in the pulp by drying to
distinguish pulp made from whole tomatoes from that made from trimming
stock. For instance, if the specific gravity or index of refraction of
a filtrate prepared from a pulp of unknown origin, and the per cent
of solids in the pulp by drying, do not agree approximately with the
relation between these determinations as shown in Table 5, it may be
assumed that the sample was not prepared from whole tomatoes, or that
some other substance, such as salt, has been added. Moreover, trimming
stock pulp rarely conforms to the relations found in whole tomato pulp.
For instance, the insoluble solids are usually higher and the acid
lower in trimming stock pulp.


Trimming Stock Pulp

In Table 3 are given the results of the examination of 21 typical
samples of trimming stock pulp prepared at different plants and in
different localities. This table is of especial interest in showing
that the relations between the results of the various analytical
determinations differ from those of whole tomato pulps as given in
Table 5. For instance, in No. 1470 the immersion refractometer reading
is 45.90, and the per cent of solids is 9.54, whereas, according to
Table 5, the per cent of solids in the pulp corresponding to an index
of refraction of 45.90 should be 8.57. The specific gravity of the
pulp is 1.0373, which, according to Table 5, should correspond to 8.98
instead of 9.54. Of course it cannot be said definitely that a pulp
which on examination is found to conform to all the relations shown
in Table 5 is necessarily whole tomato pulp. It is entirely possible
for an occasional sample of trimming stock pulp to conform to all the
relations shown in that table; moreover, the extent to which different
samples of trimming stock pulp will vary from the relations shown in
Table 5 differs with the manner of preparation. For instance, if a
portion of the juice is discarded in the manufacture of trimming stock
pulp, as is still the practice of some manufacturers, the variation
from whole tomato pulp will be greater than otherwise and the variation
will increase with the amount of juice discarded.


Methods of Analysis[2]

These methods may also be applied to the examination of raw tomatoes
and canned tomatoes. In applying the relations given below to the
results obtained by the examination of tomato pulp or canned tomatoes,
it is assumed that no substance such as sugar or salt has been added.
If salt is found to be present in excess of the amount normal to
tomatoes (from 0.05 to 0.1 per cent), it is necessary to determine the
amount and make correction therefor before applying the relations given
below.

[2] This chapter is largely taken from an article by Bigelow and
Fitzgerald, published in the Journal of Industrial and Engineering
Chemistry. The section on Microscopic Examination is substantially
a reprint of an article by Bigelow and Donk published in the trade
papers in September, 1918. For further information on the analysis of
tomato products the Methods of Analysis of the Association of Official
Agricultural Chemists (1919) should be consulted.

In examining raw tomatoes, care must be taken to secure a
representative sample of the juice. This cannot be done by applying
pressure directly, as the juice of the seed receptacles is of different
composition from that of the fleshy part of the tomato. It is
necessary, therefore, to crush the sample and thoroughly cook it in a
flask surrounded by boiling water and connected with a reflux condenser.


Microscopic Examination

The laboratory of the National Canners’ Association is frequently asked
to examine samples of tomato products to determine whether or not they
comply with the Government requirements. In examining these samples we
use the Government method (the Howard method), but do not participate
in the discussions regarding its merits and shortcomings.

It is our experience that skilled analysts can check themselves and
each other with reasonable accuracy, and it is our duty to tell the
manufacturer whether his product is legal. Should the Bureau of
Chemistry adopt some other method as preferable to the Howard method,
it would be our duty to use the new method and continue to serve the
industry by telling the manufacturer whether samples submitted by him
would pass the Government tests.

With a full understanding of our attitude in this matter many
manufacturers of tomato products send samples from time to time for
examination. It is made plain in every instance that the results
obtained by the examination of a particular sample refer only to the
batch from which that sample was taken and may give no indication of
the character of any other batch.

Some manufacturers of tomato products use the Howard method as a check
on their factory control. For this purpose it is not satisfactory to
have samples examined in a laboratory located at a distance from the
factory. Even if several samples are examined from a day’s run, they
probably do not represent all the pulp manufactured on that day. It
sometimes happens that one wagonload of tomatoes is almost entirely
free of rotting material, whereas the succeeding load contains a
considerable amount. Even with inefficient sorting, the pulp made
from the first load will show a low microscopic count whereas,
unless sorting is exceptionally good, the pulp made from the second
load may show a high count. Thus one batch may readily comply with
the requirements of the Bureau of Chemistry and the next batch may
be outside of those limits. Because of this fact this laboratory
recommends that manufacturers of tomato pulp do not rely upon the
microscopic results of a single sample. The only way in which the
product may be absolutely controlled by means of the microscopic count
is to examine a sample from each batch—that is, from each kettleful or
tankful that is evaporated. This is manifestly impossible. It would
require several analysts for one plant. Moreover, it is entirely
unnecessary.

It has been found that much better results can be secured by having
an analyst in the plant to examine samples from time to time. Then,
whenever the microscopic count becomes excessive, he can locate the
trouble and see that it is corrected.

Manufacturers who desire frequent analyses of their products,
therefore, should employ an analyst and arrange to have him instructed
in a laboratory conversant with the Howard method as used by the
Government. The laboratory of the National Canners’ Association makes
it a practice to give the necessary instruction in this method to
analysts employed by members of the association. These analysts should
be carefully selected. Other things being equal, better results should
be expected of a college graduate or at least one who has had college
training in biology and chemistry. It has been repeatedly demonstrated,
however, that a carefully selected man or woman with common school
education can learn the method and use it with sufficient accuracy for
factory control. The person selected for this work should have good
powers of observation and a positive character.

This laboratory has heretofore advised that manufacturers of tomato
pulp should not give too much attention to the microscopic count of
their product. We have maintained that the expense would be better
placed on the sorting belt; that if the sorting and trimming were
adequately done, the plant maintained in a sanitary condition and the
product manufactured as rapidly as possible, a low microscopic count
would be assured. This we still maintain is true. So many cases have
come to our attention, however, in which canners have not succeeded
in maintaining the degree of sorting necessary with a product of this
kind that we have grown to feel that the presence of an analyst working
continuously in a plant is an additional safeguard.

The conditions attending the canning of tomatoes are widely different
from those attending the manufacture of tomato pulp. The ordinary rot
is almost always apparent from the outside of the tomatoes[3] and is
removed by the peelers when preparing tomatoes for canning. Practically
none of it, therefore, finds its way into the can. With pulp it is
quite different. Any rot which is not removed by sorting and trimming
goes into the cyclone and passes into the pulp. With trimming stock
pulp, the condition is obviously much worse than with whole tomato
pulp. One hundred pounds of tomatoes will yield not far from 85 pounds
of cyclone juice. If only trimming stock is made into pulp, however,
nearly half the tomatoes are used for canning and the remainder (50 or
55 pounds of trimming stock) will only make something like 35 or 40
pounds of cyclone juice. Yet, since the rot is almost entirely on the
outside of the tomatoes, this 35 or 40 pounds made from the trimming
stock contains the same amount of molds as the 85 pounds manufactured
from the whole tomatoes. The mold count of the trimming stock pulp,
therefore, is much higher than that of whole tomato pulp made from the
same raw product.

[3] Tomatoes are sometimes found with rotten centers of which there
is little or no external evidence. This is unusual, however, and
the influence of this form of rot under manufacturing conditions is
negligible.

The Bureau of Chemistry condemns tomato pulp whose microscopic
examination gives results as high as the following figures:

    Molds                66 per cent of fields.
    Bacteria            100 million per cubic centimeter.
    Yeasts and spores   125 per 1/60 cubic millimeter.

These figures, of course, apply to the Howard method as employed by
the Bureau of Chemistry. The method is entirely arbitrary and results
agreeing with those obtained by the Bureau of Chemistry can be obtained
only by using this method substantially as it is used by the bureau.
An examination of the pulp, therefore, by an analyst who is not
thoroughly conversant with this method as it is employed by the Bureau
of Chemistry not only is useless but may actually afford a manufacturer
a false sense of security which will be greatly to his disadvantage.


Microscopic Equipment Required

The apparatus employed by the Bureau of Chemistry includes apochromatic
objectives and compensating oculars. In 1914 it became impossible to
obtain these accessories[4] because of the European war and equivalent
apparatus of American manufacture was found to give the same results.
Both of these forms of apparatus are recognized in the official Howard
method which is given below.

[4] Apochromatic objectives may now be obtained but are more expensive
than the achromatic.

This laboratory made a careful study of the accessories available in
order to determine what could best be used. It was found that very
satisfactory results could be obtained by employing a 10X Huyghenian
ocular and a 4 mm. achromatic objective (working distance 0.6 mm.) and
a 16 mm. achromatic objective. These accessories require a careful
adjustment of light, but with proper use enable an analyst to secure
satisfactory results. It is found that the best results are obtained
with a rather dark field.

The apparatus necessary for the Howard method, including the
accessories mentioned above, may be obtained of two American
manufacturers, the Bausch & Lomb Optical Company, of Rochester, N. Y.,
and the Spencer Lens Company, of Buffalo, N. Y.

There is given below a full list of the optical apparatus required,
including catalog numbers of the two manufacturers, as far as numbers
have been assigned by them to the various items. In addition to the
apparatus given in this list, the analyst should have a 50 c. c.
graduated cylinder for measuring and diluting samples. This may be
obtained of any dealer in chemical apparatus and at many drug stores.
When ordering the optical apparatus the full description as given below
should be included.


Optical Apparatus for the Howard Method

 Quantity                           Item                 Bausch &
 desired                                                   Lomb Spencer
    1     Microscope without oculars,
             objectives or other a                          FF      44
    1     Abbe condenser with two iris diaphragms
             (lower and upper)                            1740     300
    1     Double nosepiece                                1844     450
    1     16 mm. achromatic objective                     1021     108
    1     4 mm. achromatic objective with working
             distance of 0.6 mm.                          1029     116
    1     8 mm. achromatic objective with working
             distance of 1.6 mm.                          1027     112
    1     10X Huyghenian ocular                           1104     142
    1     Mechanical stage                                2116     485
    1     Substage lamp with Daylite glass                1774     385-B
    1     Blood counting chamber (Haemacytometer with
             ruling of Thoma, Neubauer, Jappert, Brewer
             or Turk)                                     3550    1472
    6     Cover glasses for same, 20×21 mm., 0.4 thick    3595    1460
    1     Howard’s mold counting chamber (with ¾ inch
             inner disk) for same                         3566   Special
    6     Cover glasses for same 33 mm. square,
             0.6 mm. thick                                3598   Special
    2     Cases for counting chambers                     3580    1505

All analysts undertaking the Howard method should secure copies of the
two bulletins of the United States Department of Agriculture written
by Mr. B. J. Howard—Bulletin 569 on Sanitary Control of Tomato Canning
Factories and Bulletin 581, Microscopic Studies on Tomato Products.
These bulletins may be obtained from the Superintendent of Documents,
Government Printing Office, Washington, D. C., on payment of five cents
each in coin.

The details of the method as given below are reprinted from the Methods
of Analysis of the Official Agricultural Chemists as amended in 1921.


Apparatus

 (_a_) _Compound microscope_.—Equipped with apochromatic objectives and
 compensating oculars, giving magnifications of approximately 90, 180,
 and 500 diameters. These magnifications can be obtained by the use
 of 16 and 8 mm. Zeiss apochromatic objectives with X6 and X18 Zeiss
 compensating oculars, or their equivalents, such as the Spencer 16 and
 8 mm. apochromatic objectives[5] with Spencer X10 and X20 compensating
 oculars, the draw-tube of the microscope being adjusted as directed
 below.

 (_b_) Thoma-Zeiss blood counting cell.[2]

 (_c_) Howard mold counting cell.—Constructed like a blood-counting
 cell but with the inner disk (which need not be ruled) about 19 mm. in
 diameter.[6]

[5] We are informed that the Bausch and Lomb Optical Co. also furnishes
suitable apochromatic objectives and compensating oculars for use in
counting molds, yeast and bacteria by the Howard method.

[6] Comment by authors: In using these cells the plane parallel cover
glasses furnished with them by maker should be used instead of the
ordinary microscope cover-glasses, since the latter are subject to
curvatures that introduce errors in the thickness of the mounts.

Molds.—Tentative

 Clean the special Howard cell so that Newton’s rings are produced
 between the slide and the cover-glass. Remove the cover and place, by
 means of a knife blade or scalpel, a small drop of the sample upon the
 central disk; spread the drop evenly over the disk and cover with the
 cover-glass so as to give an even spread to the material. It is of the
 utmost importance that the drop be mixed thoroughly and spread evenly;
 otherwise the insoluble matter, and consequently the molds, are most
 abundant at the center of the drop. Squeezing out of the more liquid
 portions around the margin must be avoided. In a satisfactory mount
 Newton’s rings should be apparent when finally mounted and none of
 the liquid should be drawn across the moat and under the cover-glass.

 Place the slide under the microscope and examine with a magnification
 of about 90 diameters and with such adjustment that each field of
 view covers 1.5 sq. mm. This area is of vital importance and may be
 obtained by adjusting the draw-tube in such a way that the diameter of
 the field becomes 1.382 mm. as determined by measurement with a stage
 micrometer.[7] A 16 mm. Zeiss apochromatic objective with a Zeiss X6
 compensating ocular or a Spencer 16 mm. apochromatic objective with a
 Spencer X10 compensating ocular, or their equivalents, shall be used
 to obtain this magnification. Under these conditions the amount of
 liquid examined is .15 cmm. per field. Observe each field as to the
 presence or absence of mold filaments and note the result as positive
 or negative. Examine at least 50 fields, prepared from two or more
 mounts. No field should be considered positive unless the aggregate
 length of the filaments present exceeds approximately one-sixth of the
 diameter of the field. Calculate the proportion of positive fields
 from the results of the examination of all the observed fields and
 report as percentage of fields containing mold filaments.

[7] Comment by authors: Obviously after the proper draw-tube length has
been secured that adjustment should be noted and always used in making
mold counts.


Yeasts and Spores.—Tentative

 Fill a graduated cylinder with water to the 20 cc. mark, and then add
 the sample till the level of the mixture reaches the 30 cc. mark.
 Close the graduate, or pour the contents into an Erlenmeyer flask,
 and shake the mixture vigorously for 15 to 20 seconds. To facilitate
 thorough mixing the mixture should not fill more than three-fourths of
 the container in which the shaking is performed. For tomato sauce or
 pastes, or products running very high in the number of organisms, or
 of heavy consistency, 80 cc. of water should be used with 10 cc. or 10
 grams of the sample. In the case of exceptionally thick or dry pastes,
 it may be necessary to make an even greater dilution.

 Pour the mixture into a beaker. Thoroughly clean the Thoma-Zeiss
 counting cell so as to give good Newton’s rings. Stir thoroughly
 the contents of the beaker with a scalpel or knife blade, and then,
 after allowing to stand 3 to 5 seconds, remove a small drop and place
 upon the central disk of the Thoma-Zeiss counting cell and cover
 immediately with the cover-glass, observing the same precautions in
 mounting the sample as given under 28.[8] Allow the slide to stand
 not less than 10 minutes before beginning to make the count. Make the
 count with a magnification of about 180 diameters to obtain which the
 following combination, or their equivalents, should be employed: 8 mm.
 Zeiss apochromatic objective with X6 Zeiss compensating ocular, or an
 8 mm. Spencer apochromatic objective with X10 Spencer compensating
 ocular with draw-tube not extended.

 Count the number of yeasts and spores[9] on one-half of the ruled
 squares on the disk (this amounts to counting the number in 8 of the
 blocks, each of which contains 25 of the small ruled squares). The
 total number thus obtained equals the number of organisms in 1/60,000
 cc. if a dilution of 1 part of the sample with 2 parts of water is
 used. If a dilution of 1 part of the sample with 8 parts of water is
 used the number must be multiplied by 3. In making the counts, the
 analyst should avoid counting an organism twice when it rests on a
 boundary line between two adjacent squares.

[8] This number refers to the section as given in the Methods of
Analysis of the Association of Agricultural Chemists.

[9] Comment by authors: The organisms counted as “yeasts and spores”
are the yeast cell and yeast and mold spores, not bacteria spores.


Bacteria.—Tentative

 Estimate the number of rod-shaped bacteria from the mounted sample
 used in 29[10] (yeasts and spores), but before examination allow
 the sample to stand not less than 15 minutes after mounting. Employ
 a magnification of about 500, which may be obtained by the use of
 an 8 mm. Zeiss apochromatic objective with X18 Zeiss compensating
 ocular with draw-tube not extended, or an 8 mm. Spencer apochromatic
 objective with X20 Spencer compensating ocular and a tube length of
 190, or their equivalents.[11]

 Count and record the number of bacteria having a length greater than
 one and one-half times their width in an area consisting of five of
 the small size squares. Count five such areas, preferably one from
 near each corner of the ruled portion of the slide and one from near
 the center. Determine the total number of the rod-shaped bacteria per
 area in the five areas and multiply by 480,000. This gives the number
 of this type of bacteria per cc. If a dilution of 1 part of the sample
 with 8 parts of water instead of 1 part of the sample with 2 parts of
 water is used in making up the sample, then the total count obtained
 as above must be multiplied by 1,440,000. Omit the micrococcus type of
 bacteria in making the count. Thus far it has proved impracticable to
 count the micrococci present, as they are likely to be confused with
 other bodies frequently present in such products.

[10] This number refers to the section as given in the Methods of
Analysis of the Association of Official Agricultural Chemists.

[11] The 4 mm. achromatic objective and the 10X ocular as given in the
list of apparatus may also be used to secure this magnification.


Determination of Total Solids


1. BY THE EXAMINATION OF THE PULP

The total solids in tomato pulp may be determined by drying _in vacuo_
at 70° C.; by drying at atmospheric pressure at the temperature of
boiling water; by calculation from the specific gravity of the pulp; or
from the per cent of solids, specific gravity or index of refraction of
the filtrate. The solids obtained by different methods on 31 samples of
pulp are given in Table 4.

(_a_) _By drying._—By drying either _in vacuo_ or at atmospheric
pressure, it is our experience that after the sample has reached
apparent dryness, four hours’ drying gives complete results. From 2 to
4 grams should be taken for the determination, and enough water added
to distribute the sample uniformly over the bottom of a flat-bottomed
dish at least 2.5 inches in diameter.

The solids as determined by drying _in vacuo_ at 70° C. are about 108.5
per cent of the result obtained by drying at the temperature of boiling
water at atmospheric pressure. This figure is the average of the
results obtained by the examination of 20 samples of pulp, in all of
which the per cent of solids obtained by drying _in vacuo_ agree quite
closely with the per cent obtained by drying at atmospheric pressure
multiplied by 1.085. In 15 of the 20 samples examined, the difference
did not exceed 0.10 per cent, and in only one case did it exceed 0.20
per cent. The results obtained by the subsequent examination of a
considerable number of other samples confirm this relation.

(_b_) _By calculation from the specific gravity of the pulp._—There is
a very exact relation between the specific gravity of pulp (determined
by the method given above) and the per cent of total solids as
determined by drying. The solids corresponding to pulps of various
specific gravities are given in Table 5, or may be obtained from the
following formula which is derived from the same table:

 Per cent Solids = 228 (sp. gr. of pulp - 1.000) + 19.1 (sp. gr. of
 pulp - 1.015).


2. BY THE EXAMINATION OF THE FILTRATE

If a sample of pulp of considerable size be thrown on a folded filter,
a filtrate is obtained whose composition has a definite relation to
that of the whole pulp.

(_a_) _By drying._—The per cent of solids in the filtrate may be
determined by drying _in vacuo_ at 70° C, or under atmospheric pressure
at the temperature of boiling water.

As in the case of the drying of pulp, a constant relation is found
to exist between the per cent of solids in the filtered liquor as
determined by drying _in vacuo_ at 70° C., and the per cent of solids
as determined by drying at atmospheric pressure at the temperature
of boiling water. The per cent of solids in the filtrate obtained by
drying at atmospheric pressure, multiplied by 1.125, gives the per cent
of solids obtained by drying _in vacuo_. This relation is shown in
detail in Table 5.


TABLE 2.—_Composition of Whole Tomato Pulps_

=======================================
        |   Composition of pulps      |
        +-------+---------------------+
        |Sp. gr.|  Total   |Insoluble |
 Sample |  at   | solids(a)|  solids  |
  No.   |20° C. |          |          |
        |       |          |          |
        |       |          |          |
--------+-------+----------+----------+
        |       |_Per cent_|_Per cent_|
 1290   | 1.0252|    5.94  |    0.66  |
 1291   | 1.0273|    6.54  |    0.78  |
 1292   | 1.0234|    5.50  |    0.80  |
 1293   | 1.0293|    7.02  |    0.74  |
 1294   | 1.0272|    6.48  |    0.69  |
        |       |          |          |
 1295   | 1.0361|    8.67  |    0.95  |
 1296   | 1.0380|    9.00  |    1.06  |
 1297   | 1.0465|   11.20  |    1.19  |
 1299   | 1.0417|   10.07  |    1.23  |
 1300   | 1.0322|    7.70  |    0.93  |
        |       |          |          |
 1301   | 1.0312|    7.36  |    0.91  |
 1302   | 1.0310|    7.45  |    0.91  |
 1303   | 1.0340|    8.17  |    0.91  |
 1304   | 1.0292|    6.88  |    0.88  |
 1305   | 1.0371|    9.03  |    1.19  |
        |       |          |          |
 1306   | 1.0370|    8.95  |    0.98  |
 1307(b)| 1.0328|    7.86  |    1.01  |
 1481   | 1.0449|   10.82  |          |
 1482   | 1.0444|   10.83  |          |
 1483   | 1.0464|   11.21  |          |
        |       |          |          |
 1484   | 1.0423|   10.27  |          |
 1485   | 1.0347|    8.55  |          |
 1477(c)| 1.0610|   13.86  |          |
 1479   | 1.0411|   10.00  |    1.21  |
 1486   | 1.0169|    4.34  |    0.62  |
        |       |          |          |
 1491   | 1.0198|    4.97  |    0.63  |
 1496   | 1.0341|    8.27  |    1.15  |
 1515   | 1.0352|    8.56  |    1.15  |
 1529   | 1.0209|    5.11  |    0.89  |
        |       |          |          |
 1530   | 1.0252|    6.21  |    0.98  |
 1531   | 1.0291|    7.17  |    1.08  |
 1224(c)| 1.0486|   11.22  |    0.91  |
 1325   | 1.0327|    7.86  |    0.93  |
--------+-------+----------+----------+

=================================================================
        |                  Filtrate from pulps                  |
 Sample +--------+----------+----------+----------+-------------+
 No.    |Sp. gr. |                     |  Acid    | Immersion   |
        |  at    |          |          |   as     |refractometer|
        | 20° C. | Solids(a)| Sugar(d) | citric   |  17.5° C.   |
--------+--------+----------+-------------------+---------------+
        |        |_Per cent_|_Per cent_|_Per cent_|             |
 1290   | 1.0233 |    5.24  |    2.41  |    0.58  |    36.24    |
 1291   | 1.0252 |    5.71  |    3.10  |    0.53  |    37.80    |
 1292   | 1.0211 |    4.88  |    2.48  |    0.49  |    34.51    |
 1293   | 1.0276 |    6.28  |    3.35  |    0.61  |    40.04    |
 1294   | 1.0256 |    5.82  |    3.20  |    0.55  |    38.27    |
        |        |          |          |          |             |
 1295   | 1.0340 |    7.69  |    4.36  |    0.67  |    46.03    |
 1296   |        |    8.05  |    4.47  |    0.66  |    46.86    |
 1297   | 1.0446 |   10.27  |    5.61  |    0.89  |    56.70    |
 1299   | 1.0394 |    9.09  |    4.96  |    0.81  |    51.75    |
 1300   | 1.0304 |    6.88  |    3.55  |    0.67  |    42.84    |
        |        |          |          |          |             |
 1301   |        |    6.68  |    3.27  |    0.69  |    41.56    |
 1302   | 1.0293 |    6.61  |    3.43  |    0.64  |    41.76    |
 1303   | 1.0323 |    7.29  |    3.77  |    0.71  |    44.65    |
 1304   | 1.0274 |    6.20  |    3.03  |    0.64  |    39.74    |
 1305   |        |    7.98  |    4.14  |    0.82  |    47.30    |
        |        |          |          |          |             |
 1306   |        |    8.01  |    4.71  |    0.69  |    47.60    |
 1307(b)| 1.0308 |    6.97  |    3.79  |    0.66  |    43.15    |
 1481   | 1.0421 |    9.64  |    5.15  |    0.99  |    54.20    |
 1482   | 1.0422 |    9.86  |    5.62  |    0.94  |    54.75    |
 1483   | 1.0441 |   10.19  |    5.67  |    0.98  |    56.45    |
        |        |          |          |          |             |
 1484   | 1.0396 |    9.23  |    5.42  |    0.81  |    52.10    |
 1485   | 1.0332 |    7.73  |    4.35  |    0.72  |    45.85    |
 1477(c)| 1.0579 |   12.75  |    6.55  |    0.97  |    67.15    |
 1479   | 1.0386 |    8.96  |          |          |    51.57    |
 1486   | 1.0158 |    3.76  |          |          |             |
        |        |          |          |          |             |
 1491   | 1.0188 |    4.40  |          |          |    32.67    |
 1496   | 1.0318 |    7.31  |          |          |    44.86    |
 1515   | 1.0331 |    7.61  |          |          |    46.20    |
 1529   | 1.0195 |    4.54  |          |          |    32.96    |
        |        |          |          |          |             |
 1530   | 1.0231 |    5.42  |          |          |    36.31    |
 1531   | 1.0273 |    6.27  |          |          |    40.09    |
 1224(c)| 1.0468 |   10.33  |          |          |    57.62    |
 1325   |        |    6.99  |          |          |    43.80    |
--------+--------+----------+----------+----------+-------------+

========================================================================
        |         |          |   Solids of filtrate        |           |
        |         |          +----------+------------------+-----------+
        |  Ratio  |Insoluble |          |          | Ratio | Refractive|
 Sample | of pulp |solids in |          |          | sugar |  constant |
  No.   |solids to|  total   | Sugar(d) |   Acid   |to acid|of filtered|
        | filtrate|  solids  |          |          |       |  liquor(f)|
        |  solids |          |          |          |       |           |
--------+---------+----------+----------+----------+-------+-----------+
        |         |_Per cent_|_Per cent_|_Per cent_|       |           |
 1290   | 1.133   |   11.1   |    46.0  |   11.1   |   4.1 |   0.20556 |
 1291   | 1.145   |   11.9   |    54.3  |    9.4   |   5.8 |   0.20550 |
 1292   | 1.127   |   14.6   |    50.8  |   10.1   |   5.0 |   0.20564 |
 1293   | 1.118   |   10.5   |    53.4  |    9.7   |   5.5 |   0.20548 |
 1294   | 1.113   |   10.6   |    55.0  |    9.5   |   5.8 |   0.20525 |
        |         |          |          |          |       |           |
 1295   | 1.127   |   11.0   |    56.8  |    8.7   |   6.5 |   0.20534 |
 1296   | 1.117   |   11.8   |    55.5  |    8.2   |   6.8 |           |
 1297   | 1.091   |   10.6   |    54.6  |    8.9   |   6.3 |   0.20544 |
 1299   | 1.108   |   12.2   |    54.6  |    8.9   |   6.1 |   0.20550 |
 1300   | 1.119   |   12.1   |    51.6  |    9.7   |   5.3 |   0.20546 |
        |         |          |          |          |       |           |
 1301   | 1.102   |   12.4   |    48.9  |   10.3   |   4.8 |           |
 1302   | 1.127   |   12.2   |    51.9  |    9.7   |   5.4 |   0.20551 |
 1303   | 1.120   |   11.1   |    51.7  |    9.7   |   5.3 |   0.20549 |
 1304   | 1.110   |   12.8   |    48.9  |   10.4   |   4.7 |   0.20546 |
 1305   | 1.132   |   13.2   |    51.9  |   10.3   |   5.0 |           |
        |         |          |          |          |       |           |
 1306   | 1.117   |   11.0   |    58.8  |    8.7   |   6.8 |           |
 1307(b)| 1.126   |   12.9   |    54.4  |    9.5   |   5.7 |   0.20544 |
 1481   | 1.123   |          |    53.4  |   10.3   |   5.2 |   0.20545 |
 1482   | 1.100   |          |    57.0  |    9.6   |   6.0 |   0.20554 |
 1483   | 1.100   |          |    55.6  |    9.6   |   5.8 |   0.20550 |
        |         |          |          |          |       |           |
 1484   | 1.114   |          |    58.7  |    8.8   |   6.7 |   0.20544 |
 1485   | 1.106   |          |    56.3  |    9.3   |   6.0 |   0.20529 |
 1477(c)| 1.111(e)|          |    51.4  |    7.7   |   6.7 |           |
 1479   | 1.116   |    9.8   |          |          |       |   0.20554 |
 1486   | 1.154   |   14.3   |          |          |       |           |
        |         |          |          |          |       |           |
 1491   | 1.128   |   12.7   |          |          |       |   0.20565 |
 1496   | 1.131   |   13.9   |          |          |       |   0.20554 |
 1515   | 1.125   |   13.5   |          |          |       |   0.20556 |
 1529   | 1.125   |   17.4   |          |          |       |   0.20556 |
        |         |          |          |          |       |           |
 1530   | 1.145   |   15.8   |          |          |       |   0.20553 |
 1531   | 1.143   |   15.1   |          |          |       |   0.20547 |
 1224(c)| 1.124(e)|   11.8   |          |          |       |           |
 1325   | 1.123   |          |          |          |       |           |
--------+---------+----------+----------+----------+-------+-----------+

  (a) Determined by drying _in vacuo_ at 70°C.
  (b) Composite of 1290 to 1306, inclusive.
  (c) This sample contained salt.
  (d) Expressed as invert.
  (e) Salt-free ratio.
  (f) Calculated by formula of Lorentz-Lorenz, (n^2 - 1)/(n^2 + 2)2.

  Note.—All specific gravities in this bulletin are on a 20°C/20°C basis.


TABLE 3.—_Composition of Trimming Stock Pulps_

============================================
           |   Composition of pulps        |
           +---------+----------+----------+
 Sample No.|Specific | Total    |Insoluble |
           |  gravity|solids(a) | solids   |
           |at 20° C.|          |          |
+----------+---------+----------+----------+
           |         |_Per cent_|_Per cent_|
 1470      |   1.0373|    9.54  |          |
 1471      |   1.0385|    9.40  |          |
 1470-1    |   1.0349|    8.56  |          |
 1470-2    |   1.0316|    7.88  |          |
 1470-3    |   1.0284|    7.00  |          |
           |         |          |          |
 1470-4    |   1.0258|    6.62  |          |
 1471-1    |   1.0334|    8.12  |          |
 1471-2    |   1.0258|    6.41  |          |
 1471-3    |   1.0229|    7.48  |          |
 1471-4    |   1.0191|    4.74  |          |
           |         |          |          |
 1572      |   1.0424|   10.28  |          |
 1573      |   1.0392|    9.53  |    1.22  |
 1574      |   1.0427|   10.29  |    1.17  |
 1575      |   1.0386|    9.73  |    1.29  |
 1662(b)   |   1.0204|    4.85  |    0.18  |
           |         |          |          |
 1664(c)   |   1.0577|   13.20  |    0.62  |
 1665      |   1.0331|    7.74  |    1.10  |
 701       |   1.0200|    4.89  |    0.72  |
 703(d)    |   1.0180|    4.24  |    0.10  |
 705       |   1.0388|    9.85  |    1.83  |
 706       |   1.0333|    8.35  |    0.98  |
+----------+---------+----------+----------+

=====================================================================
           |   Composition of liquor obtained by filtering pulps    |
           +---------+----------+----------+----------+-------------+
 Sample No.|Specific |          |          |   Acid   |  Immersion  |
           | gravity |          |          |    as    |refractometer|
           |at 20° C.|Solids(a) | Sugar(e) |  citric  |     at      |
           |         |          |          |          |  17.5° C.   |
+----------+---------+----------+----------+----------+-------------+
           |         |_Per cent_|_Per cent_|_Per cent_|             |
 1470      |   1.0337|     7.68 |    4.11  |    0.58  |       45.90 |
 1471      |   1.0334|     7.62 |    4.05  |    0.59  |       45.75 |
 1470-1    |   1.0302|     7.11 |          |          |       42.87 |
 1470-2    |   1.0279|     6.55 |          |          |       40.75 |
 1470-3    |         |     5.83 |          |          |       37.80 |
           |         |          |          |          |             |
 1470-4    |   1.0232|     5.53 |          |          |       36.40 |
 1471-1    |   1.0288|     6.86 |          |          |       41.60 |
 1471-2    |   1.0227|     5.41 |          |          |       36.10 |
 1471-3    |   1.0275|     6.14 |          |          |       39.25 |
 1471-4    |   1.0168|     3.94 |          |          |       30.35 |
           |         |          |          |          |             |
 1572      |   1.0400|     9.28 |          |          |       52.47 |
 1573      |   1.0369|     8.53 |          |          |       49.33 |
 1574      |   1.0401|     9.29 |          |          |       52.40 |
 1575      |   1.0369|     8.28 |          |          |       49.37 |
 1662(b)   |   1.0201|     4.65 |          |          |       33.27 |
           |         |          |          |          |             |
 1664(c)   |   1.0566|    12.70 |          |          |       66.92 |
 1665      |   1.0304|     6.89 |          |          |       42.65 |
 701       |   1.0184|     4.29 |    2.35  |    0.30  |       32.09 |
 703(d)    |   1.0178|     4.15 |    2.32  |    0.29  |       32.09 |
 705       |   1.0359|     8.08 |    4.07  |    0.51  |       47.85 |
 706       |         |     7.29 |    3.51  |    0.46  |       44.69 |
+----------+---------+----------+----------+----------+--------------+

==================================================================
 Sample No.| Ratio of |Insoluble |  Sugar   |  Acid in |  Ratio  |
           |   pulp   |  solids  |   in     |  solids  | of acid |
           |solids to | in total |  solids  |    of    |   to    |
           | filtrate |  solids  |    of    |  liquor  |  sugar  |
           |  solids  |          |  liquor  |          |         |
+----------+----------+----------+----------+----------+---------+
           |          |_Per cent_|_Per cent_|_Per cent_|         |
 1470      |    1.241 |          |    53.5  |     7.6  |     7.0 |
 1471      |    1.233 |          |    53.2  |     7.7  |     6.9 |
 1470-1    |    1.203 |          |          |          |         |
 1470-2    |    1.203 |          |          |          |         |
 1470-3    |    1.201 |          |          |          |         |
           |          |          |          |          |         |
 1470-4    |    1.197 |          |          |          |         |
 1471-1    |    1.184 |          |          |          |         |
 1471-2    |    1.184 |          |          |          |         |
 1471-3    |    1.218 |          |          |          |         |
 1471-4    |    1.203 |          |          |          |         |
           |          |          |          |          |         |
 1572      |    1.109 |          |          |          |         |
 1573      |    1.117 |     12.8 |          |          |         |
 1574      |    1.109 |     11.4 |          |          |         |
 1575      |    1.175 |     13.3 |          |          |         |
 1662(b)   |    1.042 |      3.7 |          |          |         |
           |          |          |          |          |         |
 1664(c)   |    1.040 |      4.7 |          |          |         |
 1665      |    1.123 |     14.3 |          |          |         |
 701       |    1.140 |     14.7 |    54.8  |     7.0  |     7.8 |
 703(d)    |    1.022 |      2.4 |    55.9  |     7.0  |     8.0 |
 705       |    1.220 |     18.6 |    50.4  |     6.2  |     8.0 |
 706       |    1.145 |     11.7 |    48.3  |     6.3  |     7.6 |
+----------+----------+----------+----------+----------+---------+

  (a) Determined by drying _in vacuo_ at 70° C.
  (b) Unconcentrated tomato juice from peeling table.
  (c) No. 1662 concentrated.
  (d) Clear liquor separated from unconcentrated pulp on standing.
  (e) Expressed as invert.


TABLE 4.—_Comparison of Methods for the Determination and Calculation
of Solids in Whole Tomato Pulp_

========================================================
        |   Solids in liquor from filtered pulp        |
        +-----------+----------------------------------+
        |By drying |       Calculated from--           |
        |_in vacuo_+-------------+----------+----------+
 Sample |    at    |  Immersion  |          |          |
   No.  |  70° C.  |refractometer| Specific |Specific  |
        |          |   reading   |gravity(1)|gravity(2)|
--------+----------+-------------+----------+----------+
        |_Per cent_|  _Per cent_ |_Per cent_|_Per cent_|
 1290   |    5.24  |    5.31     |   5.35   |   5.35   |
 1291   |    5.71  |    5.67     |   5.78   |   5.80   |
 1292   |    4.88  |    4.87     |   4.85   |   4.85   |
 1293   |    6.28  |    6.21     |   6.33   |   6.35   |
 1294   |    5.82  |    5.79     |   5.87   |   5.89   |
        |          |             |          |          |
 1295   |    7.69  |    7.67     |   7.82   |   7.82   |
 1296   |    8.05  |    7.88     |    ...   |    ...   |
 1297   |   10.27  |   10.27     |  10.25   |  10.26   |
 1299   |    9.09  |    9.06     |   9.05   |   9.06   |
 1300   |    6.88  |    6.91     |   6.98   |   6.99   |
        |          |             |          |          |
 1301   |    6.68  |    6.59     |    ...   |    ...   |
 1302   |    6.61  |    6.64     |   6.73   |   6.74   |
 1303   |    7.29  |    7.34     |   7.42   |   7.43   |
 1304   |    6.20  |    6.16     |   6.30   |   6.30   |
 1305   |    7.98  |    7.98     |    ...   |    ...   |
        |          |             |          |          |
 1306   |    8.01  |    8.05     |    ...   |    ...   |
 1307   |    6.97  |    6.96     |   7.08   |   7.08   |
 1481   |    9.64  |    9.67     |   9.68   |   9.68   |
 1482   |    9.86  |    9.81     |   9.70   |   9.71   |
 1483   |   10.19  |   10.21     |  10.15   |  10.14   |
        |          |             |          |          |
 1484   |    9.23  |    9.15     |   9.10   |   9.11   |
 1485   |    7.73  |    7.64     |   7.63   |   7.64   |
 1479   |    8.96  |    9.03     |   8.87   |   8.88   |
 1486   |    3.76  |     ...     |   3.62   |   3.63   |
 1491   |    4.40  |    4.44     |   4.30   |   4.32   |
        |          |             |          |          |
 1496   |    7.31  |    7.39     |   7.30   |   7.31   |
 1515   |    7.61  |    7.70     |   7.60   |   7.61   |
 1529   |    4.54  |    4.52     |   4.47   |   4.49   |
 1530   |    5.42  |    5.32     |   5.30   |   5.31   |
 1531   |    6.27  |    6.25     |   6.27   |   6.28   |
 1325   |    6.99  |    7.13     |    ...   |    ...   |
--------+----------+-------------+----------+----------+

===================================================================
        |        Solids in whole pulp                             |
        +----------+-------------+--------------------------------+
        |    By    | Calculated  |   Calculated from specific     |
        |   drying |   from      |          gravity of--          |
        |_in vacuo_| immersion   +----------+----------+----------+
 Sample | at 70° C.|refractometer|Filtered  |   Whole  | Filtered |
   No.  |          |  reading    |liquor[3] |   pulp   | liquor[4)|
--------+----------+-------------+----------+----------+----------+
        |_Per cent_| _Per cent_  |_Per cent_|_Per cent_|_Per cent_|
 1290   |    5.94  |    5.95     |   6.00   |   5.97   |   5.99   |
 1291   |    6.54  |    6.36     |   6.48   |   6.47   |   6.50   |
 1292   |    5.50  |    5.47     |   5.44   |   5.52   |   5.43   |
 1293   |    7.02  |    6.96     |   7.10   |   6.98   |   7.11   |
 1294   |    6.48  |    6.49     |   6.58   |   6.45   |   6.60   |
        |          |             |          |          |          |
 1295   |    8.67  |    8.59     |   8.77   |   8.63   |   8.76   |
 1296   |    9.00  |    8.83     |    ...   |   9.11   |   ...    |
 1297   |   11.20  |   11.50     |  11.47   |  11.20   |  11.49   |
 1299   |   10.07  |   10.15     |  10.14   |  10.02   |  10.15   |
 1300   |    7.70  |    7.75     |   7.82   |   7.68   |   7.83   |
        |          |             |          |          |          |
 1301   |    7.36  |    7.38     |    ...   |   7.43   |     ...  |
 1302   |    7.45  |    7.44     |   7.54   |   7.40   |   7.55   |
 1303   |    8.17  |    8.23     |   8.33   |   8.12   |   8.32   |
 1304   |    6.88  |    6.90     |   7.06   |   6.95   |   7.06   |
 1305   |    9.03  |    8.94     |    ...   |   8.88   |    ...   |
        |          |             |          |          |          |
 1306   |    8.95  |    9.02     |    ...   |   8.86   |    ...   |
 1307   |    7.86  |    7.81     |   7.93   |   7.83   |    7.93  |
 1481   |   10.82  |   10.83     |  10.84   |  10.80   |  10.84   |
 1482   |   10.83  |   10.98     |  10.86   |  10.70   |  10.88   |
 1483   |   11.21  |   11.43     |  11.36   |  11.17   |  11.36   |
        |          |             |          |          |          |
 1484   |   10.27  |   10.25     |  10.19   |  10.17   |  10.20   |
 1485   |    8.55  |    8.56     |   8.55   |   8.30   |   8.56   |
 1479   |   10.00  |   10.10     |   9.94   |   9.88   |   9.85   |
 1486   |    4.34  |     ...     |   4.05   |   3.90   |   4.07   |
 1491   |    4.97  |    4.97     |   4.82   |   4.62   |   4.84   |
        |          |             |          |          |          |
 1496   |    8.27  |    8.28     |   8.18   |   8.15   |   8.29   |
 1515   |    8.56  |    8.63     |   8.52   |   8.40   |   8.52   |
 1529   |    5.11  |    5.06     |   5.01   |   4.90   |   5.03   |
 1530   |    6.21  |    5.97     |   5.94   |   5.97   |   5.95   |
 1531   |    7.17  |    7.01     |   7.04   |   6.92   |   7.03   |
 1325   |    7.86  |    7.99     |    ...   |   7.81   |    ...   |
--------+----------+-------------+----------+----------+----------+

  (1) From formula on page 30.
  (2) The solution factor of O’Sullivan (J. Chem. Soc., 1876, p. 129)
  was employed with slight modification. The formula employed was
  1000(_d_ - 1000) / 4.35 = per cent solids. In this formula
  _d_ = specific gravity of solution at 20° C.
  (3) From formula on page 31.
  (4) For these figures the formula of footnote 2 was employed and the
  results multiplied by 1.12


TABLE 5.—_Tomato Pulp and Filtered Liquor_

========================================================================
          Whole pulp          |            Filtrate from pulp          |
------------------------------+---------------------+---------+--------+
 Solids by drying    |        | Solids by drying    |Immersion|        |
---------------------+        +---------------------+refract- |        |
_In vacuo_|    At    |Specific|_In vacuo_|    At    | ometer  |Specific|
 at 70° C.|  atmo-   |gravity | at 70° C.|  atmo-   |reading  | gravity|
          | spheric  |  at    |          | spheric  |   at    |   at   |
          | pressure | 20° C. |          | pressure |17.5° C. |  20° C.|
          |   100° C.|        |          |   100° C |         |        |
----------+----------+--------+----------+----------+---------+--------+
_Per cent_|_Per cent_|        |_Per cent_|_Per cent_|         |        |
    3.42  |    3.15  | 1.0150 |   3.05   |   2.71   |  26.9   | 1.0133 |
    3.47  |    3.20  | 1.0152 |   3.10   |   2.75   |  27.1   | 1.0136 |
    3.53  |    3.25  | 1.0155 |   3.15   |   2.80   |  27.3   | 1.0138 |
    3.58  |    3.30  | 1.0157 |   3.20   |   2.85   |  27.5   | 1.0140 |
    3.64  |    3.35  | 1.0159 |   3.25   |   2.89   |  27.7   | 1.0142 |
          |          |        |          |          |         |        |
    3.70  |    3.41  | 1.0161 |   3.30   |   2.93   |  27.9   | 1.0144 |
    3.76  |    3.46  | 1.0163 |   3.35   |   2.97   |  28.1   | 1.0146 |
    3.81  |    3.51  | 1.0166 |   3.40   |   3.02   |  28.3   | 1.0149 |
    3.87  |    3.56  | 1.0168 |   3.45   |   3.07   |  28.6   | 1.0151 |
    3.92  |    3.61  | 1.0170 |   3.50   |   3.11   |  28.8   | 1.0153 |
          |          |        |          |          |         |        |
    3.98  |    3.67  | 1.0172 |   3.55   |   3.15   |  29.0   | 1.0155 |
    4.03  |    3.72  | 1.0174 |   3.60   |   3.20   |  29.2   | 1.0157 |
    4.09  |    3.77  | 1.0177 |   3.65   |   3.24   |  29.4   | 1.0160 |
    4.15  |    3.82  | 1.0179 |   3.70   |   3.28   |  29.6   | 1.0162 |
    4.20  |    3.87  | 1.0181 |   3.75   |   3.33   |  29.8   | 1.0164 |
          |          |        |          |          |         |        |
    4.26  |    3.93  | 1.0183 |   3.80   |   3.38   |  30.0   | 1.0166 |
    4.31  |    3.98  | 1.0185 |   3.85   |   3.42   |  30.3   | 1.0168 |
    4.37  |    4.03  | 1.0188 |   3.90   |   3.46   |  30.5   | 1.0170 |
    4.43  |    4.08  | 1.0190 |   3.95   |   3.51   |  30.7   | 1.0173 |
    4.48  |    4.13  | 1.0192 |   4.00   |   3.55   |  30.9   | 1.0175 |
          |          |        |          |          |         |        |
    4 54  |    4.18  | 1.0194 |   4.05   |   3.60   |  31.1   | 1.0177 |
    4.59  |    4.23  | 1.0197 |   4.10   |   3.64   |  31.3   | 1.0179 |
    4.65  |    4.28  | 1.0199 |   4.15   |   3.69   |  31.5   | 1.0181 |
    4.71  |    4.33  | 1.0201 |   4.20   |   3.73   |  31.7   | 1.0183 |
    4.76  |    4.38  | 1.0203 |   4.25   |   3.78   |  31.9   | 1.0185 |
          |          |        |          |          |         |        |
    4.82  |    4.44  | 1.0205 |   4.30   |   3.82   |  32.1   | 1.0188 |
    4.87  |    4.49  | 1.0208 |   4.35   |   3.86   |  32.3   | 1.0190 |
    4.93  |    4.54  | 1.0210 |   4.40   |   3.91   |  32.5   | 1.0192 |
    4.99  |    4.59  | 1.0212 |   4.45   |   3.95   |  32.7   | 1.0194 |
    5.04  |    4.64  | 1.0215 |   4.50   |   4.00   |  32.9   | 1.0196 |
----------+----------+--------+----------+----------+---------+--------+


TABLE 5.—_Tomato Pulp and Filtered Liquor_—Continued

========================================================================
          Whole pulp          |            Filtrate from pulp          |
------------------------------+---------------------+---------+--------+
 Solids by drying    |        | Solids by drying    |Immersion|        |
---------------------+        +---------------------+refract- |        |
_In vacuo_|    At    |Specific|_In vacuo_|    At    | ometer  |Specific|
 at 70° C.|  atmo-   |gravity | at 70° C.|  atmo-   |reading  | gravity|
          | spheric  |  at    |          | spheric  |   at    |   at   |
          | pressure | 20° C. |          | pressure |17.5° C. |  20° C.|
          |   100° C.|        |          |   100° C |         |        |
----------+----------+--------+----------+----------+---------+--------+
_Per cent_|_Per cent_|        |_Per cent_|_Per cent_|         |        |
    5.10  |   4.70   | 1.0217 |   4.55   |   4.04   |   33.1  | 1.0198 |
    5.16  |   4.75   | 1.0219 |   4.60   |   4.09   |   33.3  | 1.0200 |
    5.21  |   4.80   | 1.0222 |   4.65   |   4.13   |   33.6  | 1.0203 |
    5.27  |   4.85   | 1.0224 |   4.70   |   4.18   |   33.8  | 1.0205 |
    5.33  |   4.90   | 1.0226 |   4.75   |   4.22   |   34.0  | 1.0207 |
          |          |        |          |          |         |        |
    5.38  |   4.96   | 1.0228 |   4.80   |   4.26   |   34.2  | 1.0209 |
    5.44  |   5.01   | 1.0230 |   4.85   |   4.31   |   34.4  | 1.0211 |
    5.49  |   5.06   | 1.0233 |   4.90   |   4.36   |   34.6  | 1.0213 |
    5.55  |   5.11   | 1.0235 |   4.95   |   4.40   |   34.8  | 1.0216 |
    5.60  |   5.16   | 1.0237 |   5.00   |   4.44   |   35.0  | 1.0218 |
          |          |        |          |          |         |        |
    5.66  |   5.21   | 1.0240 |   5.05   |   4.49   |   35.2  | 1.0220 |
    5.72  |   5.26   | 1.0242 |   5.10   |   4.53   |   35.4  | 1.0223 |
    5.77  |   5.31   | 1.0244 |   5.15   |   4.58   |   35.6  | 1.0225 |
    5.83  |   5.36   | 1.0247 |   5.20   |   4.62   |   35.8  | 1.0227 |
    5.88  |   5.41   | 1.0249 |   5.25   |   4.66   |   36.0  | 1.0229 |
          |          |        |          |          |         |        |
    5.94  |   5.47   | 1.0251 |   5.30   |   4.71   |   36.2  | 1.0231 |
    6.00  |   5.52   | 1.0253 |   5.35   |   4.75   |   36.4  | 1.1333 |
    6.05  |   5.57   | 1.0256 |   5.40   |   4.80   |   36.6  | 1.0235 |
    6.11  |   5.62   | 1.0258 |   5.45   |   4.84   |   36.8  | 1.0238 |
    6.16  |   5.67   | 1.0260 |   5.50   |   4.89   |   37.1  | 1.0240 |
          |          |        |          |          |         |        |
    6.22  |   5.73   | 1.0263 |   5.55   |   4.93   |   37.3  | 1.0242 |
    6.28  |   5.78   | 1.0265 |   5.60   |   4.98   |   37.5  | 1.0244 |
    6.33  |   5.83   | 1.0267 |   5.65   |   5.02   |   37.7  | 1.0246 |
    6.39  |   5.88   | 1.0270 |   5.70   |   5.06   |   37.9  | 1.0249 |
    6.45  |   5.93   | 1.0272 |   5.75   |   5.11   |   38.1  | 1.0251 |
          |          |        |          |          |         |        |
    6.50  |   5.99   | 1.0274 |   5.80   |   5.15   |   38.3  | 1.0253 |
    6.56  |   6.04   | 1.0276 |   5.85   |   5.20   |   38.5  | 1.0255 |
    6.61  |   6.09   | 1.0279 |   5.90   |   5.24   |   38.7  | 1.0257 |
    6.67  |   6.14   | 1.0281 |   5.95   |   5.29   |   38.9  | 1.0259 |
    6.72  |   6.19   | 1.0283 |   6.00   |   5.33   |   39.1  | 1.0261 |
----------+----------+--------+----------+----------+---------+--------+


TABLE 5.—_Tomato Pulp and Filtered Liquor_—Continued

========================================================================
          Whole pulp          |            Filtrate from pulp          |
------------------------------+---------------------+---------+--------+
 Solids by drying    |        | Solids by drying    |Immersion|        |
---------------------+        +---------------------+refract- |        |
_In vacuo_|    At    |Specific|_In vacuo_|    At    | ometer  |Specific|
 at 70° C.|  atmo-   |gravity | at 70° C.|  atmo-   |reading  | gravity|
          | spheric  |  at    |          | spheric  |   at    |   at   |
          | pressure | 20° C. |          | pressure |17.5° C. |  20° C.|
          |   100° C.|        |          |   100° C |         |        |
----------+----------+--------+----------+----------+---------+--------+
_Per cent_|_Per cent_|        |_Per cent_|_Per cent_|         |        |
   6.78   |   6.24   | 1.0285 |   6.05   |   5.38   |  39.3   | 1.0263 |
   6.84   |   6.29   | 1.0288 |   6.10   |   5.42   |  39.5   | 1.0266 |
   6.89   |   6.35   | 1.0290 |   6.15   |   5.46   |  39.7   | 1.0268 |
   6.95   |   6.41   | 1.0292 |   6.20   |   5.51   |  39.9   | 1.0270 |
   7.01   |   6.46   | 1.0294 |   6.25   |   5.56   |  40.1   | 1.0272 |
          |          |        |          |          |         |        |
   7.06   |   6.51   | 1.0297 |   6.30   |   5.60   |  40.3   | 1.0274 |
   7.12   |   6.56   | 1.0299 |   6.35   |   5.64   |  40.6   | 1.0277 |
   7.17   |   6.61   | 1.0301 |   6.40   |   5.69   |  40.8   | 1.0279 |
   7.23   |   6.66   | 1.0304 |   6.45   |   5.73   |  41.0   | 1.0281 |
   7.28   |   6.71   | 1.0306 |   6.50   |   5.78   |  41.2   | 1.0283 |
          |          |        |          |          |         |        |
   7.34   |   6.76   | 1.0308 |   6.55   |   5.82   |  41.4   | 1.0285 |
   7.40   |   6.82   | 1.0310 |   6.60   |   5.86   |  41.6   | 1.0287 |
   7.45   |   6.87   | 1.0313 |   6.65   |   5.91   |  41.8   | 1.0290 |
   7.51   |   6.92   | 1.0315 |   6.70   |   5.95   |  42.0   | 1.0292 |
   7.56   |   6.97   | 1.0317 |   6.75   |   6.00   |  42.2   | 1.0294 |
          |          |        |          |          |         |        |
   7.62   |   7.02   | 1.0320 |   6.80   |   6.04   |  42.4   | 1.0296 |
   7.68   |   7.08   | 1.0322 |   6.85   |   6.09   |  42.6   | 1.0298 |
   7.74   |   7.13   | 1.0324 |   6.90   |   6.14   |  42.8   | 1.0300 |
   7.79   |   7.18   | 1.0326 |   6.95   |   6.18   |  43.1   | 1.0303 |
   7.85   |   7.23   | 1.0329 |   7.00   |   6.22   |  43.3   | 1.0305 |
          |          |        |          |          |         |        |
   7.90   |   7.28   | 1.0331 |   7.05   |   6.26   |  43.5   | 1.0307 |
   7.96   |   7.33   | 1.0333 |   7.10   |   6.31   |  43.7   | 1.0309 |
   8.02   |   7.38   | 1.0336 |   7.15   |   6.36   |  43.9   | 1.0311 |
   8.07   |   7.43   | 1.0338 |   7.20   |   6.40   |  44.1   | 1.0313 |
   8.12   |   7.48   | 1.0340 |   7.25   |   6.44   |  44.3   | 1.0315 |
          |          |        |          |          |         |        |
   8.18   |   7.54   | 1.0342 |   7.30   |   6.48   |  44.5   | 1.0318 |
   8.24   |   7.59   | 1.0345 |   7.35   |   6.53   |  44.7   | 1.0320 |
   8.30   |   7.64   | 1.0347 |   7.40   |   6.58   |  44.9   | 1.0322 |
   8.35   |   7.69   | 1.0349 |   7.45   |   6.62   |  45.1   | 1.0324 |
   8.40   |   7.74   | 1.0352 |   7.50   |   6.66   |  45.3   | 1.0326 |
----------+----------+--------+----------+----------+---------+--------+


TABLE 5.—_Tomato Pulp and Filtered Liquor_—Continued

========================================================================
          Whole pulp          |            Filtrate from pulp          |
------------------------------+---------------------+---------+--------+
 Solids by drying    |        | Solids by drying    |Immersion|        |
---------------------+        +---------------------+refract- |        |
_In vacuo_|    At    |Specific|_In vacuo_|    At    | ometer  |Specific|
 at 70° C.|  atmo-   |gravity | at 70° C.|  atmo-   |reading  | gravity|
          | spheric  |  at    |          | spheric  |   at    |   at   |
          | pressure | 20° C. |          | pressure |17.5° C. |  20° C.|
          |   100° C.|        |          |   100° C |         |        |
----------+----------+--------+----------+----------+---------+--------+
_Per cent_|_Per cent_|        |_Per cent_|_Per cent_|         |        |
   8.46   |   7.79   | 1.0354 |   7.55   |   6.71   |   45.5  | 1.0328 |
   8.52   |   7.84   | 1.0356 |   7.60   |   6.76   |   45.7  | 1.0331 |
   8.57   |   7.89   | 1.0358 |   7.65   |   6.80   |   45.9  | 1.0333 |
   8.63   |   7.95   | 1.0361 |   7.70   |   6.84   |   46.2  | 1.0335 |
   8.68   |   8.00   | 1.0363 |   7.75   |   6.89   |   46.4  | 1.0337 |
          |          |        |          |          |         |        |
   8.74   |   8.05   | 1.0365 |   7.80   |   6.93   |   46.6  | 1.0339 |
   8.80   |   8.11   | 1.0367 |   7.85   |   6.98   |   46.8  | 1.0341 |
   8.86   |   8.16   | 1.0370 |   7.90   |   7.02   |   47.0  | 1.0344 |
   8.91   |   8.21   | 1.0372 |   7.95   |   7.07   |   47.2  | 1.0346 |
   8.96   |   8.26   | 1.0374 |   8.00   |   7.11   |   47.4  | 1.0348 |
          |          |        |          |          |         |        |
   9.02   |   8.31   | 1.0377 |   8.05   |   7.16   |   47.6  | 1.0350 |
   9.08   |   8.36   | 1.0379 |   8.10   |   7.20   |   47.8  | 1.0352 |
   9.14   |   8.41   | 1.0381 |   8.15   |   7.24   |   48.0  | 1.0354 |
   9.19   |   8.46   | 1.0383 |   8.20   |   7.28   |   48.2  | 1.0357 |
   9.25   |   8.51   | 1.0386 |   8.25   |   7.33   |   48.4  | 1.0359 |
          |          |        |          |          |         |        |
   9.30   |   8.57   | 1.0388 |   8.30   |   7.38   |   48.6  | 1.0361 |
   9.36   |   8.62   | 1.0390 |   8.35   |   7.42   |   48.8  | 1.0363 |
   9.42   |   8.67   | 1.0393 |   8.40   |   7.46   |   49.0  | 1.0366 |
   9.47   |   8.72   | 1.0395 |   8.45   |   7.51   |   49.2  | 1.0368 |
   9.53   |   8.77   | 1.0397 |   8.50   |   7.55   |   49.4  | 1.0370 |
          |          |        |          |          |         |        |
   9.58   |   8.83   | 1.0400 |   8.55   |   7.60   |   49.6  | 1.0372 |
   9.64   |   8.88   | 1.0402 |   8.60   |   7.64   |   49.8  | 1.0374 |
   9.70   |   8.93   | 1.0404 |   8.65   |   7.68   |   50.0  | 1.0376 |
   9.75   |   8.98   | 1.0406 |   8.70   |   7.73   |   50.2  | 1.0379 |
   9.80   |   9.03   | 1.0408 |   8.75   |   7.78   |   50.4  | 1.0381 |
          |          |        |          |          |         |        |
   9.86   |   9.09   | 1.0410 |   8.80   |   7.82   |   50.7  | 1.0383 |
   9.92   |   9.14   | 1.0413 |   8.85   |   7.86   |   50.9  | 1.0385 |
   9.97   |   9.19   | 1.0415 |   8.90   |   7.91   |   51.1  | 1.0387 |
  10.02   |   9.24   | 1.0417 |   8.95   |   7.95   |   51.3  | 1.0389 |
  10.08   |   9.29   | 1.0419 |   9.00   |   8.00   |   51.5  | 1.0392 |
----------+----------+--------+----------+----------+---------+--------+


TABLE 5.—_Tomato Pulp and Filtered Liquor_—Continued

========================================================================
          Whole pulp          |            Filtrate from pulp          |
------------------------------+---------------------+---------+--------+
 Solids by drying    |        | Solids by drying    |Immersion|        |
---------------------+        +---------------------+refract- |        |
_In vacuo_|    At    |Specific|_In vacuo_|    At    | ometer  |Specific|
 at 70° C.|  atmo-   |gravity | at 70° C.|  atmo-   |reading  | gravity|
          | spheric  |  at    |          | spheric  |   at    |   at   |
          | pressure | 20° C. |          | pressure |17.5° C. |  20° C.|
          |   100° C.|        |          |   100° C |         |        |
----------+----------+--------+----------+----------+---------+--------+
_Per cent_|_Per cent_|        |_Per cent_|_Per cent_|         |        |
  10.14   |  9.35    | 1.0421 |   9.05   |   8.05   |  51.7   | 1.0394 |
  10.19   |  9.40    | 1.0424 |   9.10   |   8.09   |  51.9   | 1.0396 |
  10.25   |  9.45    | 1.0426 |   9.15   |   8.13   |  52.1   | 1.0398 |
  10.30   |  9.50    | 1.0428 |   9.20   |   8.18   |  52.3   | 1.0400 |
  10.35   |  9.55    | 1.0430 |   9.25   |   8.22   |  52.5   | 1.0402 |
          |          |        |          |          |         |        |
  10.41   |  9.60    | 1.0433 |   9.30   |   8.27   |  52.7   | 1.0404 |
  10.47   |  9.65    | 1.0435 |   9.35   |   8.31   |  52.9   | 1.0406 |
  10.52   |  9.70    | 1.0437 |   9.40   |   8.35   |  53.1   | 1.0409 |
  10.58   |  9.75    | 1.0440 |   9.45   |   8.40   |  53.3   | 1.0411 |
  10.64   |  9.80    | 1.0442 |   9.50   |   8.45   |  53.5   | 1.0413 |
          |          |        |          |          |         |        |
  10.70   |  9.86    | 1.0444 |   9.55   |   8.49   |  53.7   | 1.0415 |
  10.75   |  9.91    | 1.0447 |   9.60   |   8.53   |  53.9   | 1.0417 |
  10.80   |  9.96    | 1.0449 |   9.65   |   8.58   |  54.1   | 1.0419 |
  10.86   | 10.01    | 1.0451 |   9.70   |   8.62   |  54.3   | 1.0422 |
  10.91   | 10.06    | 1.0453 |   9.75   |   8.67   |  54.5   | 1.0424 |
          |          |        |          |          |         |        |
  10.97   | 10.11    | 1.0456 |   9.80   |   8.71   |  54.7   | 1.0426 |
  11.02   | 10.16    | 1.0458 |   9.85   |   8.75   |  55.0   | 1.0428 |
  11.08   | 10.21    | 1.0461 |   9.90   |   8.80   |  55.2   | 1.0430 |
  11.14   | 10.26    | 1.0463 |   9.95   |   8.85   |  55.4   | 1.0433 |
  11.20   | 10.31    | 1.0465 |  10.00   |   8.89   |  55.6   | 1.0435 |
          |          |        |          |          |         |        |
  11.25   | 10.37    | 1.0467 |  10.05   |   8.93   |  55.8   | 1.0437 |
  11.30   | 10.42    | 1.0469 |  10.10   |   8.98   |  56.0   | 1.0439 |
  11.36   | 10.47    | 1.0472 |  10.15   |   9.02   |  56.2   | 1.0441 |
  11.41   | 10.52    | 1.0474 |  10.20   |   9.07   |  56.4   | 1.0444 |
  11.47   | 10.57    | 1.0476 |  10.25   |   9.11   |  56.6   | 1.0446 |
          |          |        |          |          |         |        |
  11.53   | 10.63    | 1.0478 |  10.30   |   9.15   |  56.8   | 1.0448 |
  11.59   | 10.68    | 1.0481 |  10.35   |   9.20   |  57.0   | 1.0450 |
  11.64   | 10.73    | 1.0483 |  10.40   |   9.25   |  57.2   | 1.0452 |
  11.70   | 10.78    | 1.0485 |  10.45   |   9.29   |  57.4   | 1.0454 |
  11.75   | 10.83    | 1.0487 |  10.50   |   9.33   |  57.6   | 1.0457 |
----------+----------+--------+----------+----------+---------+--------+


TABLE 5.—_Tomato Pulp and Filtered Liquor_—Continued

========================================================================
          Whole pulp          |            Filtrate from pulp          |
------------------------------+---------------------+---------+--------+
 Solids by drying    |        | Solids by drying    |Immersion|        |
---------------------+        +---------------------+refract- |        |
_In vacuo_|    At    |Specific|_In vacuo_|    At    | ometer  |Specific|
 at 70° C.|  atmo-   |gravity | at 70° C.|  atmo-   |reading  | gravity|
          | spheric  |  at    |          | spheric  |   at    |   at   |
          | pressure | 20° C. |          | pressure |17.5° C. |  20° C.|
          |   100° C.|        |          |   100° C |         |        |
----------+----------+--------+----------+----------+---------+--------+
_Per cent_|_Per cent_|        |_Per cent_|_Per cent_|         |        |
  11.81   |  10.89   | 1.0490 |  10.55   |   9.38   |   57.8  | 1.0459 |
  11.87   |  10.94   | 1.0492 |  10.60   |   9.42   |   58.0  | 1.0461 |
  11.93   |  10.99   | 1.0494 |  10.65   |   9.47   |   58.2  | 1.0463 |
  11.99   |  11.04   | 1.0496 |  10.70   |   9.51   |   58.4  | 1.0465 |
  12.05   |  11.09   | 1.0499 |  10.75   |   9.55   |   58.6  | 1.0467 |
          |          |        |          |          |         |        |
  12.10   |  11.15   | 1.0501 |  10.80   |   9.60   |   58.8  | 1.0469 |
  12.15   |  11.20   | 1.0503 |  10.85   |   9.65   |   59.0  | 1.0471 |
  12.21   |  11.25   | 1.0505 |  10.90   |   9.70   |   59.2  | 1.047| |
  12.26   |  11.30   | 1.0508 |  10.95   |   9.74   |   59.4  | 1.0476 |
  12.32   |  11.35   | 1.0510 |  11.00   |   9.78   |   59.6  | 1.0478 |
          |          |        |          |          |         |        |
  12.37   |  11.40   | 1.0512 |  11.05   |   9.82   |   59.9  | 1.0480 |
  12.43   |  11.45   | 1.0515 |  11.10   |   9.87   |   60.1  | 1.0482 |
  12.49   |  11.50   | 1.0517 |  11.15   |   9.92   |   60.3  | 1.0484 |
  12.55   |  11.55   | 1.0519 |  11.20   |   9.96   |   60.5  | 1.0487 |
  12.60   |  11.60   | 1.0522 |  11.25   |  10.00   |   60.7  | 1.0489 |
          |          |        |          |          |         |        |
  12.65   |  11.66   | 1.0524 |  11.30   |  10.04   |   60.9  | 1.0491 |
  12.71   |  11.71   | 1.0526 |  11.35   |  10.09   |   61.1  | 1.0493 |
  12.77   |  11.76   | 1.0528 |  11.40   |  10.13   |   61.3  | 1.0495 |
  12.83   |  11.81   | 1.0531 |  11.45   |  10.18   |   61.5  | 1.0498 |
  12.88   |  11.86   | 1.0533 |  11.50   |  10.22   |   61.7  | 1.0500 |
          |          |        |          |          |         |        |
  12.94   |  11.92   | 1.0535 |  11.55   |  10.27   |   61.9  | 1.0502 |
  12.99   |  11.97   | 1.0538 |  11.60   |  10.31   |   62.1  | 1.0504 |
  13.05   |  12.02   | 1.0540 |  11.65   |  10.35   |   62.3  | 1.0506 |
  13.10   |  12.07   | 1.0542 |  11.70   |  10.40   |   62.5  | 1.0508 |
  13.16   |  12.12   | 1.0544 |  11.75   |  10.45   |   62.7  | 1.0511 |
          |          |        |          |          |         |        |
  13.22   |  12.18   | 1.0547 |  11.80   |  10.49   |   62.9  | 1.0513 |
  13.27   |  12.23   | 1.0549 |  11.85   |  10.53   |   63.1  | 1.0515 |
  13.32   |  12.28   | 1.0551 |  11.90   |  10.58   |   63.3  | 1.0517 |
  13.38   |  12.33   | 1.0554 |  11.95   |  10.63   |   63.5  | 1.0519 |
  13.44   |  12.38   | 1.0556 |  12.00   |  10.67   |   63.7  | 1.0521 |
----------+----------+--------+----------+----------+---------+--------+


TABLE 5.—_Tomato Pulp and Filtered Liquor_—Continued

========================================================================
          Whole pulp          |            Filtrate from pulp          |
------------------------------+---------------------+---------+--------+
 Solids by drying    |        | Solids by drying    |Immersion|        |
---------------------+        +---------------------+refract- |        |
_In vacuo_|    At    |Specific|_In vacuo_|    At    | ometer  |Specific|
 at 70° C.|  atmo-   |gravity | at 70° C.|  atmo-   |reading  | gravity|
          | spheric  |  at    |          | spheric  |   at    |   at   |
          | pressure | 20° C. |          | pressure |17.5° C. |  20° C.|
          |   100° C.|        |          |   100° C |         |        |
----------+----------+--------+----------+----------+---------+--------+
_Per cent_|_Per cent_|        |_Per cent_|_Per cent_|         |        |
  13.50   |  12.44   | 1.0558 |  12.05   |  10.71   |  64.0   | 1.0523 |
  13.55   |  12.49   | 1.0560 |  12.10   |  10.75   |  64.2   | 1.0525 |
  13.60   |  12.54   | 1.0562 |  12.15   |  10.80   |  64.4   | 1.0527 |
  13.66   |  12.59   | 1.0565 |  12.20   |  10.84   |  64.6   | 1.0529 |
  13.72   |  12.64   | 1.0567 |  12.25   |  10.89   |  64.8   | 1.0531 |
          |          |        |          |          |         |        |
  13.78   |  12.70   | 1.0569 |  12.30   |  10.94   |  65.0   | 1.0533 |
  13.83   |  12.75   | 1.0572 |  12.35   |  10.98   |  65.2   | 1.0535 |
  13.89   |  12.80   | 1.0574 |  12.40   |  11.02   |  65.4   | 1.0537 |
  13.95   |  12.85   | 1.0576 |  12.45   |  11.07   |  65.6   | 1.0539 |
  14.01   |  12.90   | 1.0579 |  12.50   |  11.11   |  65.8   | 1.0541 |
-----------------------------------------------------------------------+


The per cent of solids in the filtered liquor obtained by drying _in_
_vacuo_, multiplied by 1.12, gives the per cent of solids in the
original pulp obtained by drying _in vacuo_. This relationship is shown
in Table 2, in the column headed “Ratio of pulp solids to filtrate
solids,” and also in Table 5.

Of the 33 samples shown in Table 2, the result obtained by multiplying
the per cent of solids in the filtrate (obtained by drying _in vacuo_)
by the factor 1.12 is very nearly identical with the per cent of solids
in the pulp (obtained by drying _in vacuo_). In 22 of the 33 samples
the difference between these two figures is less than 0.1 per cent. In
17 samples it is less than 0.06 per cent, and in 13 samples it is less
than 0.05 per cent. In only two samples does it exceed 0.17 per cent.

(_b_) _By calculation from the specific gravity of the filtrate._—The
specific gravity of the filtered liquor may be determined by means of
an ordinary pycnometer. From the specific gravity at 20° C., the per
cent of solids in the filtrate as determined by drying _in vacuo_ at
70° C. may be obtained from Table 5. It may also be calculated by the
following formula, which was derived from the same table:

 Per cent Solids in Filtrate = 230 (sp. gr. of filtrate - 1.000).

The per cent of solids in the pulp may also be ascertained from the
specific gravity of the filtrate at 20° C., from Table 5. The same
results may be obtained from the following formula, which was derived
from Table 4:

 Per cent Solids in Pulp =
    257.5 (sp. gr. of filtrate at 20° C. - 1.000).

It is of interest to note that the table suggested by Windisch for the
determination of extract in wine (Bureau of Chemistry, U. S. Dept.
Agri., Bull. 107, revised, Table V) may be employed to determine solids
in tomato pulp from the specific gravity of the filtered liquor from
the same. If the specific gravity of the liquor be determined at 20°
C., the figures in the adjoining column, under “Extract,” correspond
very closely to the per cent of total solids in the original pulp. A
still closer agreement is obtained if the figure 0.05 be deducted from
the percentage of extract given in the table.

(_c_) _By calculation from the index of refraction of the
filtrate._—The index of refraction of the liquor obtained by filtering
tomato pulp may be determined by means of either the Zeiss-Abbé
refractometer, or the immersion refractometer at the temperature
of 17.5° C. The latter is preferable as it permits of much greater
accuracy. The corresponding percentage of solids in the filtrate and
the percentage of solids in the pulp from which it is prepared may be
ascertained from the index of refraction by Table 5. The per cent of
solids in the filtrate may also be calculated from the scale reading of
the immersion refractometer at 17.5° C. by the following formula, which
is derived from Table 5:

 Per cent Solids in Filtrate =
    0.258 (scale reading - 15) - 0.0165(scale reading - 26.4).

If the index of refraction has been determined by means of an Abbé
refractometer, the per cent of solids in the filtrate may be calculated
by the following formula:

 Per cent Solids in Filtrate =
    666(n_{D} - 1.3332) - 20.7(n_{D} - 1.3376).

The per cent of total solids in tomato pulp may also be ascertained
from the index of refraction of the liquor prepared by filtering the
pulp as shown in Table 5; or it may be calculated from the immersion
refractometer reading by the following formula, which is derived from
Table 5:

 Per cent Solids in Pulp =
   0.289(scale reading of filtrate - 15) - 0.0185(scale reading - 26.4).

If the index of refraction of the filtrate has been determined by
means of an Abbé refractometer, the per cent of solids in the pulp may
be calculated by the following formula:

 Per cent Solids in Pulp = 748(n_{D} - 1.3332) - 25.5(n_{D} - 1.3376).

It is of interest to note that the relation between the index of
refraction of the liquor obtained by filtering tomato pulp and the per
cent of solids in that liquid is very similar to the relation between
the index of refraction and dissolved solids in beer and wine extract,
as shown in the table prepared by Wagner.[12]

[12] “Ueber quantitative Bestimmungen wässeriger Lösungen mit dem
Zeiss-schen Eintauch-refraktometer,” Table XVII.

In the formula given above, as well as in Table 5, it is assumed
that salt is absent. If it be desired to calculate the percentage of
solids in a sample containing salt from the index of refraction of
the filtrate, it is necessary first to determine the amount of salt
present and make correction therefor (see p. 34). For this purpose the
table of Wagner[13] may be employed. The correction of the immersion
refractometer reading amounts to 0.45 for each tenth per cent of salt
present.

[13] _Ibid._, Table I.

This correction is necessary if the percentage of solids be determined
by drying, or calculated from specific gravity.


Determination of Insoluble Solids

 Transfer 20 grams of the pulp to an eight-ounce nursing bottle, nearly
 filled with hot water, mix by shaking, and centrifuge until the
 insoluble matter is collected in a cake in the bottom of the bottle.
 Transfer the supernatant liquor onto a double, tared filter paper
 covering the bottom of a Büchner funnel, using suction to facilitate
 filtration.

 Again fill the nursing bottle with hot water, stir the cake of
 insoluble solids so that it is thoroughly mixed with the water,
 centrifuge, and decant the supernatant liquor on the filter. Repeat
 the centrifuging and the filtration of the supernatant liquor once
 more, and then finally transfer the insoluble solids to the filter
 paper and thoroughly wash with hot water. Dry the paper and insoluble
 solids, and weigh. The insoluble solids are quite hydroscopic and the
 weight must be taken quickly.


Determination of Sugar

The sugar of tomatoes is probably always present as invert sugar. If
cane sugar is ever present in the raw product it is doubtless inverted
during the concentration of pulp. The per cent of sugar given in Tables
2 and 3 was determined by the method of Munson and Walker.[14]

[14] Methods of Analysis of the Association of Official Agricultural
Chemists (1919).


Determination of Acidity

Accurate results cannot be obtained by the titration of tomato products
in the presence of the insoluble solids. If it be desired to determine
the acidity in the entire sample of tomatoes or tomato pulp rather than
in the expressed juice, the insoluble solids should first be removed
by the method given in the determination of insoluble solids or by
filtration through filter paper. The per cent of acid given in Tables
2 and 3 was obtained by titrating the liquor obtained by filtering the
pulp. In products of this nature, the addition of an alkali causes a
brownish color which has a tendency to obscure the end point shown
by the indicator. To obviate this, the sample should be diluted to
at least 200 cc. and a larger amount of indicator employed than is
necessary with a clear solution. The following details are suggested.

 Dilute 20 grams of the filtrate under examination with over 200
 cc. of water. Add at ½ cc. of phenolphthalein solution (prepared
 by dissolving 1 gram of phenolphthalein in 100 cc. of 95 per cent
 alcohol) and titrate with sodium hydroxide until the end point is
 obtained. Add 1 cc. of tenth-normal hydrochloric acid, heat the
 solution quickly to boiling and boil one minute to expel carbon
 dioxide. Cool the solution quickly to about room temperature, and then
 add tenth-normal sodium hydroxide until the end point is obtained.
 The volume of hydrochloric acid added must, of course, be taken into
 consideration in the final result. The filtrate may also be titrated
 direct with tenth-normal sodium hydroxide solution with satisfactory
 results.


Determination of Salt

This laboratory has been using the following rapid method which gives
results agreeing closely with results obtained by the analysis of the
ash:

 Weigh out 20 grams of pulp, dilute in a volumetric flask to 200 cc.,
 filter and titrate an aliquot portion with standard silver nitrate
 solution, using potassium chromate as indicator. The acidity of tomato
 pulp is not sufficient to interfere with this determination.


DETERMINATION OF SPECIFIC GRAVITY[15]

[15] All specific gravities given in this bulletin are on a 20°C/20°C
basis.

The specific gravity of tomato pulp is used as one criterion for
establishing the value of pulp that is offered for sale and is also
used in connection with the manufacture of pulp to determine the point
at which evaporation should be stopped.

In the former case there is ample time for making the examination,
and conditions may be established which permit a reasonable degree of
accuracy in the work.

In the determination of the specific gravity of hot pulp during the
process of its evaporation speed is essential, and the conditions of
a manufacturing plant do not always permit a high degree of accuracy.
It becomes necessary, therefore, to consider what methods may give the
highest degree of accuracy obtainable under the conditions of the work
and at the same time afford quick results.

Tomato pulp, owing to its high viscosity, retains a large quantity of
air bubbles which increase the volume of the pulp and hence interfere
with the accuracy of the determination of specific gravity. In working
with cold pulp this air may be eliminated by whirling in a centrifuge.
With hot pulp that operation is impossible, and the specific gravity
must be determined in the presence of the air bubbles mentioned.
Moreover, in working with cold pulp the temperature can be more
accurately controlled, and the error caused by variation in temperature
can be corrected. With hot pulp these conditions cannot be obtained
nearly so well. The determination of specific gravity of hot pulp is
therefore only roughly approximate at best. Where time permits it is
strongly advisable to cool the pulp under conditions that prevent
evaporation before determining specific gravity.

The importance of accuracy in the determination of specific gravity in
tomato pulp is discussed on page 50.

Methods are given below for the determination of specific gravity in
both hot and cold pulp.

When salt has been added, the amount should be determined and a
correction applied by deducting .007 from the specific gravity for each
per cent of salt present.


(a) <sc>COLD PULP AFTER CENTRIFUGING TO ELIMINATE AIR BUBBLES</sc>

This method may be employed for pulp of any degree of concentration
or for unconcentrated cyclone juice. A specific gravity flask such as
is shown in Figure 1 is used together with a “2-bottle” Babcock milk
tester (the centrifuge referred to below). The flask may be obtained of
Eimer & Amend, Third Avenue, 18th to 19th Streets, New York City, or of
Emil Greiner & Co., 55 Fulton Street, New York City, and in ordering
it should be designated as “specific gravity flask for tomato pulp of
Pyrex glass with a capacity of about 125 cc.” The “2-bottle” Babcock
milk tester may be obtained of any dairy supply house. It may also be
obtained of any dealer in chemical apparatus by designating it as E. &
A. No. 1833.

The specific gravity flask may be calibrated as follows:

Obtain the weight of the flask after thoroughly cleaning and drying,
fill to overflowing with water (preferably boiled and cooled distilled
water) and remove the excess water from the mouth of the flask by means
of a straight edge. Wipe dry and weigh immediately. If the flask full
of water is weighed at any other temperature than 20° C. (68° F.) a
correction must be made to obtain the weight at that temperature. These
corrections are as follows:

=============================================
     Temperature     |Correction to be added
                     |with flasks having a
                     |     volume of—
----------+----------+------------+----------
Fahrenheit|Centigrade|   125 cc.  |  400 cc.
----------+----------+------------+----------
          |          |  _Grams_   | _Grams_
    69    |   20.6   |    .02     |   .05
    70    |   21.1   |    .03     |   .09
    71    |   21.7   |    .05     |   .14
    72    |   22.2   |    .06     |   .20
    73    |   22.8   |    .08     |   .25
          |          |            |
    74    |   23.3   |    .09     |   .30
    75    |   23.9   |    .11     |   .35
    76    |   24.4   |    .13     |   .41
    77    |   25.0   |    .15     |   .47
    78    |   25.6   |    .17     |   .53
          |          |            |
    79    |   26.1   |    .18     |   .59
    80    |   26.7   |    .20     |   .65
    81    |   27.2   |    .22     |   .71
    82    |   27.8   |    .24     |   .77
          |          |            |
    83    |   28.3   |    .26     |   .83
    84    |   28.9   |    .28     |   .89
    85    |   29.4   |    .30     |   .96
    86    |   30.0   |    .32     |  1.02
----------+----------+------------+----------

If it is desired to use somewhat larger samples and thus secure
correspondingly more accurate results, a similar flask, but made
somewhat larger (capacity approximately 400 cc.), may be employed. Such
a flask, with a diameter of a little over 3 inches, is illustrated in
Figure 2. This larger flask will not fit into the Babcock tester, and
when it is used a special head for the Babcock tester must be made.
Such a head is illustrated in Figure 3, and can be made by any good
tinner.

The larger flask shown in Figure 2 holds a heavier weight than the
Babcock machine is intended to carry, and the advisability of its use
is perhaps questionable. In any case, whatever size flask is used, it
is important to build a guard around the centrifuge in order to protect
the operator when the apparatus gives way, as it eventually will.

[Illustration:
Fig. 1. Small Specific Gravity Flask.
Fig. 2. Large Specific Gravity Flask.
Dimensions given are outside measurements. Thickness of walls is about
3/64 in.]

The details of the method of determining specific gravity by the use of
this apparatus are as follows:

 Fill the flask shown in Figure 1 with the sample of pulp and place
 in the centrifuge (the Babcock milk tester mentioned above). Place a
 suitable counterpoise[16] in the other receptacle of the centrifuge.
 Whirl for from one-half to one minute at a speed of about 1,000
 revolutions per minute, that is with the handle turning about 100
 revolutions per minute. Because of the air bubbles removed by
 whirling, the surface of the pulp will now be considerably below the
 top of the flask. Fill the flask and whirl in the centrifuge again.
 Repeat this filling and whirling until the flask is practically full
 of pulp after whirling. Ordinarily two or three separate whirlings are
 sufficient. Then add a few more drops of pulp so that the pulp comes
 above the top of the flask, and strike off flush with the top of the
 flask with a straight edge. Wash the outside of the flask, wipe dry,
 and weigh. Then read the specific gravity of the pulp from a table
 prepared, giving the weight of the flask full of pulp and the specific
 gravity of the pulp in parallel columns, or calculate the specific
 gravity as described below.

[16] This counterpoise may be prepared with a can or bottle weighted
with some heavy material such as solder or shot, until it balances
approximately the weight of the can full of pulp. The counterpoise,
once prepared, may be left in the centrifuge.

[Illustration: Fig. 3. Special Head and Flask Receptacles for Babcock
Milk Tester.]

 While the weight is being taken a thermometer may be placed in the
 pulp remaining in the can or dipper from which the flask was filled.
 If the temperature varies from 68° F. the specific gravity may be
 corrected by Table 8. In order to use this method the temperature of
 the pulp should not be below 50° F., or above 86° F.; otherwise, it
 should be warmed or cooled, as described above.

The method is accurate, simple, easily operated and fairly rapid. To
calculate the specific gravity from the weights obtained, the weight
of the clean, dry flask and of the water it contains at 68° F. are
necessary. The weight of the clean, dry flask is then subtracted from
the weight of the flask full of pulp to obtain the net weight of the
pulp. This divided by the weight of the water the flask will contain at
68° F., gives the specific gravity.

A table can be constructed readily for each flask, which will
give in parallel columns the weight of the flask full of pulp and
the corresponding specific gravity. This greatly simplifies the
determination, as it eliminates all calculation. When such a table is
employed a balance giving actual weights is practically as convenient
as one reading specific gravity directly. It has the very important
advantage that the balance, weights, and flask may be tested from time
to time.

In preparing such a table it is convenient first to draw a curve
representing specific gravities of the pulp and corresponding weights
of the flask full of pulp of various degrees of specific gravity. The
table may then be constructed from the curve.

For instance, let us suppose that the flask weighs 56.00 grams and
that when full of water at 68° F. (20° C.) it weighs 176.63 grams.
The water contained at the temperature mentioned then weighs (176.63
- 56.00) 120.63 grams. Now the specific gravity of the pulp is its
weight compared with the weight of an equal volume of water. Having the
figures given above we can easily calculate the weight of the flask
filled with pulp of any desired specific gravity. We may therefore
calculate the weight of the flask plus pulp of two different specific
gravities; mark those points on a sheet of coordinate paper with
specific gravity of the pulp entered at the bottom and the weight of
flask plus pulp at the side, and a straight line drawn through the two
points mentioned gives us the weight of the flask when filled with pulp
of any specific gravity.

For instance, if the flask mentioned above be filled with a pulp of the
specific gravity of 1.03, the weight of the pulp is (120.63 × 1.03)
124.25 grams. This added to the weight of the flask (56.00 grams) gives
us 180.25 grams. Similarly, if the flask be filled with pulp of 1.04
specific gravity the weight of the contents at 68° F. will be (120.63 ×
1.04) 125.46 grams. This added to the weight of the flask (56.00 grams)
gives 181.46 grams as the weight of flask plus pulp. Now if a sheet
of coordinate paper be prepared with specific gravities entered at the
bottom and weight of flask plus pulp at the side, these points may be
entered. This is done in Figure 4 and the two points mentioned are each
indicated by a circle and are connected by a straight line. A table may
be constructed from this line, giving the weights of flask plus pulp in
one column and the corresponding specific gravity in another.

[Illustration: Fig. 4. Weight and Specific Gravity of Tomato Pulp.]

As an illustration of this there are given below a series of figures
illustrating the beginning of the table that could be constructed from
Figure 4. If a large sheet of coordinate paper be taken the line shown
in Figure 4 may be extended so that a table may be constructed for pulp
of all concentrations.

        ---------+--------
        Weight of|Specific
        flask and|gravity
          pulp   |
        ---------+--------
         180.25  | 1.0300
         180.31  | 1.0305
         180.37  | 1.0310
         180.43  | 1.0315
         180.49  | 1.0320
         180.55  | 1.0325
         180.61  | 1.0330
         180.67  | 1.0335
        ---------+--------

The highest degree of accuracy can be secured by filling the flask and
making the weighing at exactly 68° F. This is obviously not practicable
under factory conditions, however, and satisfactory results can be
secured by taking the temperature of the pulp at the time of weighing
and correcting for temperature by the use of Table 8. This table gives
the correction to be added to the specific gravity when the pulp is
taken at temperatures between 68° and 86° F., and the correction to be
deducted from the specific gravity for temperatures, between 55° and
68° F. As a matter of principle, correction factors should be avoided
as far as practicable, and the smaller the correction factor the more
accurate the results will be. This table will be found especially
useful in determining the specific gravity of the partly concentrated
pulp, as is directed on page 50.

As stated above, in determining specific gravity by this method it is
advisable that the reading be made to the second place of decimals. For
this purpose an assay pulp balance is suggested. An assay pulp balance
carrying a maximum load of 300 grams is listed by dealers in chemical
apparatus at $52.50. This balance may be obtained from dealers in
chemical apparatus by designating it as “Assay pulp balance E. & A. No.
292, capacity 300 grams.” The same balance, more heavily built, and
preferable for that reason, carrying a maximum capacity of 600 grams,
is listed at $63.

A satisfactory set of weights, suitable for weighing a cup similar to
that shown in Figure 1, may be obtained from any dealer in chemical
apparatus by designating it as E. & A. No. 516, “Metric brass weights
in wooden box, 200 grams to 1 centigram.” This is listed at $5.50.

For convenience, all of the apparatus necessary for using this method
of determining specific gravity is listed below. With the exception
of the specific gravity flask this apparatus may be purchased of
any dealer in chemical supplies. The specific gravity flasks have
not heretofore been available except through this laboratory, which
purchased a considerable quantity of them and supplied them to
manufacturers of pulp as long as this supply lasted. At the urgent
request of the writer, Eimer & Amend and Emil Greiner & Co., both of
New York City, have finally stocked this item and stand ready to supply
it to those wishing to secure it.

 Specific gravity flask for tomato pulp, of Pyrex glass, 1½ × 6¼ inches
 (outside measurements), capacity about 125 cc.

 Two-bottle Babcock milk tester, with 2 brass holders, E. & A. No. 1883.

 Assay pulp balance, maximum load 300 grams, E. & A. No. 292.

 Metric brass weights in wooden box, 200 grams to 1 centigram, E. & A.
 No. 516.

 Chemical thermometer, 50 to 212° F.[17]

[17] If it is preferred a chemical thermometer with Centigrade scale
may be used having a range of from 0 to 100 degrees.


(b) COLD PULP WITHOUT CENTRIFUGING

A method frequently employed for determining the specific gravity of
cold pulp is to fill the cup by pouring, strike off with a straight
edge, wash the outside, dry and weigh. As ordinarily practiced, this
determination is attended by considerable error. If the balance is
arranged for reading specific gravity directly, weights should be at
hand for determining the accuracy of the balance and the weight of the
flask, and both should be checked from time to time. The pulp on being
poured into the flask or cup carries with it air bubbles to such an
extent as to materially reduce the weight. Attempts to remove these
air bubbles without the use of a centrifuge have not been successful.
This is shown in Table 7, in the column headed “Pouring cold and
whirling by hand.” The figures given in this column were obtained by
weighing the sample after it had been whirled vigorously in the cup
shown in Fig. 5 until air bubbles appeared to be eliminated. From 50
to 175 revolutions were given the cup in each of the determinations
whose results are shown in this column. Even then it will be noted by
comparison with Column 1 that the results are low. As the method is
ordinarily practiced in the plant, without any attempt to remove the
air bubbles by whirling, the results obtained are likely to be less
accurate than those shown in the column just mentioned.


(c) SPECIFIC GRAVITY OF HOT PULP

Many manufacturers of tomato pulp control the concentration of their
product by determining specific gravity when the evaporation is almost
completed. They therefore desire the results at the earliest possible
moment, and there is no attempt to cool the sample before determining
specific gravity, although in that way much more accurate results could
be obtained.

When necessary to use this method the hot pulp is poured into the
specific gravity flask (Fig. 1 or Fig. 2) by means of a dipper until
the flask overflows. The top is then “struck off” with a straight edge
and the flask placed in a shallow basin of water and the pulp carefully
washed from the outside. The temperature of the pulp remaining in the
dipper is then determined by means of a chemical thermometer.

The flask is then dried with a towel, which operation is greatly
facilitated by the heat of the pulp. The cooling of the contents of
the flask causes contraction, so that after washing the flask is
not entirely full. This should be disregarded, as it is desired to
determine the weight of the amount of pulp that filled the flask
originally. As soon as the outside of the flask is clean and dry the
flask and contents are weighed.

The apparent specific gravity of the hot pulp is ascertained from the
special table prepared for the flask according to the directions given
on page 38, and the correction figure for the temperature of the pulp
obtained from Table 6 is added. _For example_, this method when applied
to a certain sample of hot pulp (without centrifuging) indicated a
specific gravity of 0.9874. The temperature of the pulp was found to
be 201° F. In Table 6 we find that the correction .0457 is equivalent
to 201° F. Adding this to the apparent specific gravity given above,
we have 0.9874 × 0.457 or 1.033 which is as nearly as we can determine
from the hot pulp the specific gravity that would have been determined
by examining the same sample after cooling by method (a). More accurate
results can be obtained by working with larger specific gravity
flasks. For instance, the specific gravity cup shown in Figure 5 may be
made of copper, and may readily be made larger than the glass flasks
shown in Figures 1 and 2. All metal flasks will gradually change in
weight, owing to the solution of metal by the hot tomato pulp, and
their weight should therefore be checked from time to time.


TABLE 6.—_Corrections for Specific Gravity of Hot Pulp_

        =========+==========
        Temp. °F.|Correction
        ---------+----------
           190   |  .0401
           191   |  .0406
           192   |  .0411
           193   |  .0416
                 |
           194   |  .0421
           195   |  .0426
           196   |  .0431
           197   |  .0436
                 |
           198   |  .0441
           199   |  .0447
           200   |  .0452
           201   |  .0457
                 |
           202   |  .0462
           203   |  .0466
           204   |  .0472
           205   |  .0477
                 |
           206   |  .0482
           207   |  .0487
           208   |  .0492
           209   |  .0498
                 |
           210   |  .0504
           211   |  .0510
           212   |  .0515
        ---------+----------

With a materially larger cup or flask (which should be of metal) a
heavier balance and heavier weights should be used than suggested on
page 40. In using a specific gravity cup similar to that shown in
Figure 5 but holding about 1,000 grams of pulp an assay pulp balance
with a capacity of 1,500 can be employed, or owing to the increased
accuracy of the larger sample a less accurate and cheaper scale such as
the “Howard trip scale,” or better a box scale such as is listed as E.
& A. 338, may be employed. In working with a cup of this size a set of
weights ranging from 1000 grams to 1 centigram is necessary.

The determination of specific gravity in hot pulp is attended by
considerable error. Even if the flask or cup be carried directly to
the kettle, and filled as quickly as possible, the pulp is materially
cooled in transferring, and by the time the surface is “struck off”
sufficient contraction may occur to increase the weight of the contents
of the flask and cause material error.

When a pail of hot pulp is carried to another room or building for the
determination of specific gravity, the error caused by cooling may be
increased. Again, notwithstanding the fact that the pulp is hot, enough
air bubbles become incorporated into it in pouring into the cup to
make a considerable difference in the weight. These two errors counter
balance each other to some extent, but it is impossible to control the
manipulation with sufficient uniformity to secure satisfactory results.

[Illustration: Fig. 5. Specific Gravity Cup for Hot Pulp.]

The figures obtained in the second column of Table 7 (under the
heading “Pouring at boiling temperature”) show the error of this
method with carefully calibrated apparatus and working under the best
conditions. By comparison with the first column, it will be noted
that the results are always low, and that the difference between
individual determinations is so great that a correction factor cannot
be established. It should be borne in mind that these results were
obtained by chemists. When the method is employed even by careful
operators in the plant, still greater discrepancies may be expected.


TABLE 7.—_Comparison of Different Methods of Determining Specific
Gravity_[18]

=====================================================================
      |Specific gravity by different methods of filling cup or flask.
Sample+---------------+---------------+---------------+--------------
Number| Centrifuging  | Pouring cold  |  Pouring at   |  Dipping at
      |   at 68°F.    | and whirling  |    boiling    |   boiling
      |               |    by hand    |  temperature  | temperature
------+---------------+---------------+---------------+--------------
 1477 |    1.0610     |               |    1.0464     |
  Do  |    1.0610     |               |    1.0449     |
  Do  |               |               |    1.0600     |
 1484 |    1.0423     |    1.0330     |    1.0380     |
 1485 |    1.0347     |               |    1.0336     |
 1483 |    1.0464     |    1.0437     |    1.042      |
  Do  |               |    1.0420     |    1.0446     |
  Do  |               |    1.0430     |               |
  Do  |               |    1.0442     |               |
 1482 |    1.0441     |    1.0416     |    1.0360     |
  Do  |    1.0444     |    1.0419     |    1.0410     |
  Do  |    1.0447     |    1.0424     |    1.0413     |
 1481 |    1.0449     |    1.0410     |    1.040      |
  Do  |    1.0449     |    1.0410     |    1.041      |
  Do  |               |    1.0418     |    1.0397     |
 1480 |               |    1.0430     |    1.036      |
  Do  |               |    1.0420     |    1.040      |
  Do  |               |    1.0429     |    1.044      |
  Do  |               |               |    1.0407     |
 1496 |    1.0340     |    1.0330     |               |
  Do  |    1.0341     |    1.0326     |               |
  Do  |               |    1.0326     |               |
  Do  |               |    1.0346     |               |    1.0299
  Do  |               |    1.0341     |               |    1.0303
  Do  |               |    1.0341     |               |    1.0343
  Do  |               |               |               |    1.033
 1515 |    1.0351     |               |               |    1.036
  Do  |    1.0352     |               |               |    1.035
 1519 |    1.0380     |               |               |    1.0377
  Do  |               |               |               |    1.0383
  Do  |               |               |               |    1.0329
  Do  |               |               |               |    1.0350
 1521 |    1.0440     |               |    1.0410     |    1.0439
  Do  |               |               |    1.0439     |    1.0448
 1522 |    1.0500     |               |    1.0428     |    1.0493
  Do  |               |               |    1.0455     |    1.0508
 1524 |    1.0519     |               |               |    1.0504
 1524 |               |               |               |    1.0529
  Do  |               |               |               |    1.0510
 1526 |    1.0519     |               |    1.0472     |    1.0529
  Do  |               |               |    1.0463     |    1.0525
 1528 |    1.0519     |               |    1.0509     |    1.0514
  Do  |               |               |    1.0485     |    1.0514
 1530 |    1.0252     |               |    1.0281     |    1.0260
  Do  |               |               |               |    1.0264
  Do  |               |               |               |    1.0269
 1531 |    1.0291     |               |    1.0312     |    1.0294
  Do  |               |               |               |    1.0311
  Do  |               |               |               |    1.0313
------+---------------+---------------+---------------+--------------

[18] Table 7 gives the results obtained in the determination of
specific gravity of several samples of pulp by different methods. The
specific gravity given in the first column under the head “Centrifuging
at 68° F.” has been proved to be correct by other analytical methods.
It will be noted that where duplicate determinations are given in this
column they agree with each other very closely. The errors in the other
methods in determining specific gravity are shown in the remaining
columns. It will be noted that the duplicates given in these columns
vary materially from each other.

It should be stated that the results given under the heading “Pouring
cold and whirling by hand” were obtained by much more careful work than
is practicable in the factory. The flasks in which the determination
was made were equipped with a bail, as shown in Fig. 5. page 44, and
the samples were whirled by hand until air bubbles were eliminated
as far as practicable by that method. The results, in this column
are therefore much more accurate than are obtained by the method as
ordinarily practiced.

It was thought that better results might be secured by modifying the
construction of a cup in such a manner as to permit it to be filled by
dipping below the surface of the pulp in the kettle. A bail made of
3/16-inch wire was, therefore, soldered to the opposite side of the cup
(see Fig. 5). By means of the bail the cup was lowered into the kettle.
After it was filled with the pulp the attempt was made to remove air
bubbles by repeatedly giving the bail a quick twist or circular motion
with a sudden stop. The cup was then brought quickly to the surface of
the kettle and “struck off” with a straight edge, the outside of the
cup and bail washed quickly with water, dried, and the cup and contents
weighed.

In using this method the steam is turned off, and as soon as the foam
subsides the cup is sunk well below the surface of the pulp. At this
time the heat in various portions of the kettle is of course uniform,
by reason of the thorough mixture caused by the vigorous boiling. Owing
to the large mass of rather viscous material, and the heat of the
kettle itself, the contents of the kettle cool slowly, and even after
10 minutes the temperature does not decrease more than 1° F., except at
the very surface of the pulp. As a result of several observations, it
was found that a thermometer bulb held 3 inches below the surface of
the pulp showed a lowering of temperature of not more than 1° F. in 10
minutes and a lowering of only 0.5° F. in from 5 to 7 minutes.

The bail employed was about 6½ inches wide and 8 inches long. There
was some difficulty, owing to the pulp spattering on the hands of
the operator because of the air escaping from the cup. This might be
diminished by the use of a longer bail, or by wearing suitable gloves.
When evaporating tanks are used it will probably be necessary to attach
the bail to a stick or support of some kind. In addition to permitting
this method of filling, the bail has the additional advantage that
the cup full of pulp may be handled for washing and conveying to the
balance much more conveniently and with less danger of spilling than
with the handle on the side of the cup. Again, the bail does not heat
when the cup is filled with hot pulp, and for that reason is easier to
handle.


(d) HYDROMETER METHOD

Hydrometers are of little value in determining the specific gravity
of tomato pulp. With cold pulp they cannot be used at all. With hot
pulp a relatively slender hydrometer comes to rest and readings can
be taken with more or less accuracy. The value of the reading is
relative to the specific gravity of the pulp and varies with the shape
of the hydrometer and with the character of the pulp. It is necessary
therefore to obtain the relation between the reading of the hydrometer
in the hot pulp and the specific gravity (obtained by an accurate
method) of the same pulp cooled without evaporation. In the hands of a
careful operator some manufacturers have found hydrometers (used with
hot pulp) helpful in making pulp of uniform specific gravity.

The hydrometer gives much more accurate results with the filtrate of
pulp. As shown on page 31, there is a direct relation between the
specific gravity of tomato pulp and of the liquor obtained by filtering
or straining the same, so that when the specific gravity of the latter
is known that of the former may be ascertained readily by means of
a table. This method is peculiarly applicable to the examination of
cyclone juice and light pulp from which the insoluble solids may be
removed quickly by straining through a cloth, and it therefore affords
the most rapid method that is available to the average factory for
determining the specific gravity of cyclone juice.

In Table 8 are given a series of corrections making it possible to use
this method at any temperature between 50 and 80° Fahrenheit. The more
closely the readings are taken to 68° F. the more accurate the results.
Moreover, when it is attempted to strain the insoluble solids from
hot pulp or cyclone juice, considerable evaporation occurs, causing
concentration of the product and producing an error in the results.
When hot pulp is handled, therefore, it must be strained as quickly
as possible, and more accurate results may be obtained if the pulp
is cooled quickly before straining. This may be done by placing in a
large can and stirring vigorously while the can stands in ice water, or
shaking under water in a large flask.

There are several forms of hydrometer which may be used for determining
the specific gravity of the filtrate. The ordinary specific gravity
hydrometer is the most logical form to use, since it gives the specific
gravity directly. Unfortunately, specific gravity hydrometers with the
particular marking required for this work are not a stock article, and
would, therefore, have to be made to order. For this reason they would
be difficult to obtain and not easily replaced if broken.

The Brix hydrometer appears to solve the difficulty. This hydrometer
has no direct relation to specific gravity, but Brix readings can,
of course, be converted to the specific gravity readings by a table
arranged in parallel columns. Table 9 gives the specific gravity of
tomato pulp and the corresponding Brix reading of the filtrate. The
Brix hydrometer gives directly the per cent of sugar in a solution of
cane sugar, one degree Brix being equivalent to one per cent sugar at
the temperature for which the hydrometer was calibrated. This fact and
the ordinary purpose for which the instrument is manufactured are of no
interest to us in this connection, however. The Brix hydrometer of the
range desired for the examination of cyclone juice and pulp is a stock
article and can be secured readily.

The instrument can be used with the same accuracy as the specific
gravity hydrometer, and the results obtained by it, after correcting
for temperature by Table 8, are converted into terms of specific
gravity by means of Table 9. The determination of the specific
gravity of pulp by means of the hydrometer reading of the filtrate
obtained from the pulp has several advantages over the ordinary method
of weighing a measured quantity of the pulp. When applied to pulp
manufactured from whole tomatoes, the method is reasonably accurate.
It is also very rapid and the equipment required is inexpensive. This
method is especially applicable to the examination of pulp manufactured
from whole tomatoes. It is less applicable to trimming stock pulp,
although even with that product the method will be of value, especially
for the examination of cyclone juice for the purpose of controlling
concentration. With pulp manufactured from trimming stock, the relation
of the specific gravity of the pulp to the specific gravity of the
filtrate obtained from it will vary according to the nature of the
raw material used and also according to the method of manufacture. It
seems probable, therefore, that after a manufacturer has determined
this relation as applied to his own product, he may be able to use this
method with reasonable accuracy even in connection with trimming stock
pulp.

The method is adapted especially to the examination of cold pulp or
cyclone juice.

The following apparatus is used in this method:

 1 Brix hydrometer, graduated at 20.0° C., with a range of 1–10°,
 graduated in 1/10°.

 1 Cylinder of heavy glass, lipped, height 12 inches, diameter 2 inches.

 1 Chemical thermometer, graduated in Fahrenheit system up to 212° F.

Since this apparatus is likely to be broken, it is well for each plant
that contemplates using the method to equip itself with at least two of
each item mentioned above.

The Brix hydrometer mentioned above is suggested because it is a stock
article handled by all dealers in chemical apparatus and can be secured
quickly. It has the disadvantage that it is relatively large, and in
order to use it the filtrate must be prepared in much larger quantity
than would be required by a smaller hydrometer. By placing orders well
in advance with dealers in chemical apparatus special hydrometers may
be made with a bulb about one-half inch in diameter and with a total
length of five or six inches. Such hydrometers could be used with a
cylinder as small as one inch in diameter. They would require much less
liquor than is necessary for the Brix hydrometer and therefore would
enable the analyst to obtain results much more quickly. In securing
such hydrometers it would be well to order several at a time, since it
would require several weeks to replace any that may be broken.

The details of the method are as follows:

 Place a piece of cotton cloth of about the texture of ordinary glass
 toweling over a clean, dry container 10 or 12 inches in diameter or
 over a No. 10 can. Pour on the cloth a suitable amount of the pulp
 or cyclone juice to be examined, pick the cloth up by the corners
 and squeeze gently to separate the greater part of the insoluble
 solids. The strained liquid left in the vessel will be more or less
 turbid, according to the pressure exerted in squeezing. The amount of
 insoluble material producing this turbidity, however, is not usually
 sufficient to interfere with the examination of the product by means
 of a hydrometer. If, however, it is necessary to exert considerable
 pressure to get the amount of filtrate desired and the turbidity is
 therefore considerable it will be necessary to pass the liquor through
 a second filter, which, of course, may be done quickly.

 Transfer this strained liquid, which for the sake of convenience we
 will designate as “filtrate,” to the 2-inch cylinder described above,
 and lower the Brix hydrometer into it until the hydrometer floats.
 When the hydrometer, becomes stationary, the reading on the stem is
 taken. In reading the hydrometer it will be noted that, owing to
 the meniscus, the liquid immediately at the stem rises one or two
 divisions above the general surface. The reading at the lowest point
 of the surface is desired. In reading the stem, therefore, allowance
 for the meniscus should be made and a reading recorded one or two
 divisions on the scale below the extreme height of the meniscus on
 the stem. The reading so obtained is recorded as the Brix hydrometer
 reading of the filtrate.

 After determining the Brix reading of the filtrate from the tomato
 pulp, the corresponding specific gravity of the pulp may be obtained
 from Table 9. The result obtained by the method should be corrected to
 the temperature of 68° F., according to Table 8. If it is desired to
 use the reading of the filtrate from cyclone juice for the purpose of
 controlling the evaporation of tomato pulp, suitable directions are
 given below under “Evaporation to Specific Gravity Desired.”


IMPORTANCE OF ACCURACY IN DETERMINING SPECIFIC GRAVITY

The description of the tables given in the following page is intended
for those operators who desire to take the trouble to obtain the
specific gravity of raw product. Where, as is often the case, the pulp
is sold under definite specifications for specific gravity, the care
necessary to make these observations with a considerable degree of
accuracy will be found to be an economy.

If a product be shipped that is materially below the specific gravity
stipulated, the manufacturer will of course be docked and the loss
will be considerable. On the other hand, the specific gravity should
not be materially above the specifications. The buyer, who is usually
a manufacturer of ketchup, desires the pulp of the specific gravity
stipulated, and a higher degree of concentration is therefore not
a mark of superiority in pulp intended for that purpose. Moreover,
material increase in concentration above the specifications of the
purchaser causes considerable loss by reason of reduced volume. For
instance, 100 gallons of pulp with a specific gravity of 1.036 are
equivalent to 103 gallons of a pulp with a specific gravity of 1.035.
Again, 100 gallons of pulp with a specific gravity of 1.040 are
equivalent to 114.7 gallons of pulp with a specific gravity of 1.035.

When these figures are considered with reference to the entire output
of the season, it is apparent that the determination of the specific
gravity of the final product is of considerable importance, and
will warrant care and, if necessary, the employment of a man who is
competent to do the work accurately.

This is well illustrated by an experience of one of the large pulp
makers, who was selling pulp under specification of 1.035 specific
gravity. Owing partly to an error in his specific gravity apparatus, he
was actually turning out pulp of a specific gravity varying from 1.040
to 1.050. In other words, each 100 cases of pulp he delivered were
equivalent to from 115 to 126 cases of pulp of 1.035 specific gravity.
While this manufacturer was using the greater part of the pulp himself,
he had contracted to sell a considerable amount of it, and all that was
supplied before the error was noticed was sold at a loss, whereas after
the error was discovered he supplied pulp well above the specifications
of the buyer at a substantial profit. Even then his profit was not what
it should have been. His output would have been 10 per cent greater
than it was if the specific gravity of his product had just complied
with his specifications.

Another manufacturer who sold his pulp under the specification of
1.035 specific gravity, received a complaint from one of the largest
buyers of pulp in the country that the specific gravity was low. The
manufacturer then examined samples, which he had retained in his
possession, of the various runs, using the method described on page 41,
under the head of “Specific gravity of cold pulp without centrifuging.”
Seventeen samples in all were examined, and he obtained an average
specific gravity of 1.0276. The purchaser had reported a specific
gravity of 1.0315–.0039 higher than that obtained by the maker. The
manufacturer then brought duplicate samples to this laboratory and the
specific gravity was determined in all of them by the method described
on page 34, “After centrifuging to eliminate air bubbles.”

While this work was being done the manufacturer himself desired to
check the mechanical centrifuge, and attempted to remove the air
bubbles from the same samples by swinging the specific gravity cups
by hand. He made a special effort to remove the air bubbles in this
way, devoting nearly a day to the examination of the 17 samples.
Notwithstanding his unusual care, his average specific gravity was
1.0318, while the centrifuge method gave 1.0328. It will be noted
that the specific gravity as determined by the centrifuge method was
.0013 higher than that obtained by the purchaser, though the latter
used a more accurate method than has ordinarily been employed in this
determination. This difference has ordinarily been regarded in the
industry as insignificant. It is apparent that it is not negligible,
however, when we consider that the difference in yield involved amounts
to over 4.5 gallons in 100 gallons of pulp.

It is true that all these results are lower than the specifications for
which this particular pulp was sold, but the incident illustrates the
importance of an accurate determination of specific gravity.


EVAPORATION TO THE SPECIFIC GRAVITY DESIRED

Manufacturers of tomato pulp have considerable difficulty in securing
a product of uniform concentration and in determining at what point
to stop evaporation. Some manufacturers turn off the steam when it is
believed that the concentration has gone far enough and make a hasty
determination of specific gravity. If it is found the concentration
is not as great as is desired, heating is resumed for a time and the
specific gravity again determined. Others make but one determination
of specific gravity when it is believed that the desired concentration
has been reached, and if it is found to be underconcentrated, continue
the evaporation for a length of time which experience has indicated to
be necessary. Neither of these methods of operating is satisfactory.
They involve a great deal of work and the concentration of the product
obtained is not sufficiently uniform. Moreover, the determination of
specific gravity of hot pulp is very inaccurate (see p. 44).

A method of employing a gauge stick is believed to be simpler and more
practicable.

Some manufacturers who desire to work with the simplest possible
methods, even at the sacrifice of a high degree of control over the
concentration of their products, measure the volume of cyclone juice
introduced into the evaporating tank; and when it is believed that
the concentration is sufficient, measure the depth of the evaporated
product in the tank, the steam being momentarily turned off for that
purpose and the measurement being taken after the foam subsides. This
method was outlined in detail in a trade paper article published from
this laboratory in 1918. The method is somewhat inaccurate, because
it is based on the measurement of cyclone juice as it flows from the
cyclone and which therefore contains a large amount of air. This air
materially increases the volume of the pulp and consequently the
amount of finished pulp calculated from the volume of cyclone juice
containing this air is greater than can actually be obtained. Some
manufacturers of pulp have found the method practicable, however, by
making a correction based on factory experience on the amount of pulp
which the method indicates should result from the evaporation of each
bath. This method also calls for the use of measuring tanks, which
many manufacturers do not have and do not care to provide. The method
is therefore not repeated here, but the laboratory has a number of
reprints of the trade paper article which are available to any who
desire more detailed information regarding the matter.

The following method has been found more accurate and more convenient
than the one mentioned above. It has the special advantage that it is
based on the examination of the cyclone juice after the juice has been
heated to a sufficient extent to “break” the foam.

In using this method, the manner in which the cyclone juice is prepared
is immaterial. The tomatoes may be broken by steam or mechanical
breaker and may be cycloned hot or cold. The steam may be turned into
the coils as soon as they are covered and the cyclone juice may run
into the evaporating tank until the tank is filled.

Finally, when the last of the cyclone juice is added and the contents
of the tank are boiling vigorously, the steam is momentarily turned
off. The volume is then determined by means of a gauge stick and a
sample is withdrawn, filtered and the specific gravity or degrees Brix
determined as described on page 50. The extent to which evaporation
must be continued to secure pulp of the desired specific gravity is
determined by Table 9.

This table gives in the first four columns the specific gravity of the
partially concentrated pulp taken from the evaporating tank, the per
cent of solids of the same, the specific gravity of the filtrate and
the Brix reading of the filtrate. In order to use the tables, it is
only necessary to make use of one of these columns.

This method of operation can be simplified and more accurate results
obtained by equipping each evaporating tank with a one-inch gage glass
extending the full height of the tank. The gage glass should be open at
the top and connected with the bottom of the tank by a pipe equipped
with a valve. Before the tank is filled with cyclone juice the valve is
turned off and the gage glass filled with water. Steam is turned on as
soon as the pipes are covered and the foam is “broken” quickly without
trouble that was experienced in heating the tank filled with cool pulp.
The heat is continued while the tank is filled to the desired height
with the pulp. The steam is then momentarily turned off and the valve
at the top of the gage glass opened to permit the water in the gage
glass to equalize in height with the partly concentrated pulp within
the tank. The height of water in the gage glass is read by a scale
attached, the sample of the pulp taken for examination and the steam
again turned on.

There is ample time to determine the specific gravity of the sample of
partly concentrated pulp and from its volume as obtained by the gage
glass to calculate the volume to which the pulp should be evaporated
to secure the desired specific gravity in the finished product. The
specific gravity of the sample may be taken by any of the methods
described in the chapter on “Determination of specific gravity.” More
accurate results can be obtained by pouring the sample of pulp as soon
as it is taken into a large loosely stoppered flask and holding the
flask with constant agitation in a tub of ice water until it is brought
to about the temperature of the room.

Having determined the volume (when heated to the boiling point) of a
batch of cyclone juice or of pulp at any stage of its manufacture and
its specific gravity (at 68° F.), each of the last five columns of the
table gives a factor by which the volume of the partially evaporated
pulp may be multiplied to determine the volume of pulp of the specific
gravity given at the top of the column. Since both measurements are
taken at the boiling point the question of temperature need not be
considered.


Table 8.—_Corrections for Specific Gravity and Brix_[19] _Readings at
Different Temperatures to 68 Degrees F._ (_20 Degrees C._)

Corrections to be subtracted from specific gravity or degrees Brix.

        ===============+=============
          Temperature  | Corrections
        -------+-------+-------+-----
        Deg. F.|Deg. C.|Sp. Gr.|Brix.
        -------+-------+-------+-----
          50   | 10.0  | .0017 | .38
          51   | 10.6  | .0016 | .36
          52   | 11.1  | .0016 | .35
          53   | 11.7  | .0015 | .33
          54   | 12.2  | .0014 | .31
               |       |       |
          55   | 12.8  | .0014 | .30
          56   | 13.3  | .0013 | .28
          57   | 13.9  | .0012 | .26
          58   | 14.4  | .0011 | .24
               |       |       |
          59   | 15.0  | .0010 | .22
          60   | 15.6  | .0009 | .20
          61   | 16.1  | .0009 | .18
          62   | 16.7  | .0008 | .16
          63   | 17.2  | .0007 | .13
               |       |       |
          64   | 17.8  | .0006 | .11
          65   | 18.3  | .0004 | .08
          66   | 18.9  | .0003 | .05
          67   | 19.4  | .0002 | .03

          69   | 20.6  | .0002 | .03
          70   | 21.1  | .0003 | .05
          71   | 21.7  | .0004 | .08
          72   | 22.2  | .0006 | .11
          73   | 22.8  | .0007 | .15
               |       |       |
          74   | 23.3  | .0009 | .18
          75   | 23.9  | .0011 | .21
          76   | 24.4  | .0012 | .24
          77   | 25.0  | .0013 | .28
          78   | 25.6  | .0015 | .32
               |       |       |
          79   | 26.1  | .0017 | .35
          80   | 26.7  | .0018 | .39
          81   | 27.2  | .0019 | .42
          82   | 27.8  | .0021 | .46
          83   | 28.3  | .0023 | .49
               |       |       |
          84   | 28.9  | .0024 | .54
          85   | 29.4  | .0026 | .58
          86   | 30.0  | .0027 | .62
          87   | 30.6  | .0029 | .66
          88   | 31.1  | .0031 | .70
        -------+-------+-------+-----
[19] These temperature corrections are for a Brix instrument
standardized for 20°C. There are Brix hydrometers on the market
standardized for 17.5°C. Temperature corrections for a Brix hydrometer
standardized at this temperature may be obtained by correcting to
20° by means of the above table (for instrument graduated at 20°C.)
and adding to this corrected reading 0.12. For instance suppose the
reading for a 17.5° instrument is 7.00 at 25°C. The correction from
the above table will be .28 or a total of 7.28. Adding .12 to this
gives a corrected reading of 7.40. If the reading is 7.00 at 15°C.
the correction from the above table amounts to .22 (to be subtracted)
giving 6.78. Adding 0.12 to this gives the corrected reading of 6.90.


TABLE 9.—_Equivalent Volumes of Pulp of Different Degrees of
Concentration_

========================================================================
               |                | Factor by which to multiply volume of
  Tomato pulp  |   Filtrate     | pulp of given specific gravity to
               |   from pulp    | ascertain volume of pulp with
               |                | equivalent solid content and with
               |                |         specific gravity of
--------+-------+--------+-------+-------+-------+-------+-------+-------
Specific|  Per  |Specific|Degrees|       |       |       |       |
gravity | cent  |gravity |  Brix |       |       |       |       |
 at     |solids |   at   |   at  | 1.030 | 1.035 | 1.040 | 1.045 | 1.050
 68° F. |       |  68° F.| 68° F.|       |       |       |       |
--------+-------+--------+-------+-------+-------+-------+-------+-------
 1.0125 |  2.79 | 1.0108 | 2.78  | .384  | .326  | .283  | .249  | .223
 1.0130 |  2.92 | 1.0113 | 2.89  | .402  | .342  | .296  | .261  | .234
 1.0135 |  3.05 | 1.0118 | 3.02  | .420  | .357  | .310  | .273  | .244
 1.0140 |  3.17 | 1.0123 | 3.14  | .437  | .372  | .323  | .285  | .255
 1.0145 |  3.30 | 1.0128 | 3.27  | .455  | .388  | .336  | .297  | .265
        |       |        |       |       |       |       |       |
 1.0150 |  3.42 | 1.0133 | 3.40  | .472  | .401  | .348  | .306  | .274
 1.0155 |  3.54 | 1.0138 | 3.51  | .489  | .416  | .361  | .318  | .284
 1.0160 |  3.67 | 1.0143 | 3.65  | .507  | .431  | .374  | .329  | .294
 1.0165 |  3.79 | 1.0148 | 3.77  | .524  | .445  | .387  | .341  | .304
 1.0170 |  3.92 | 1.0153 | 3.90  | .542  | .460  | .400  | .352  | .315
        |       |        |       |       |       |       |       |
 1.0175 |  4.05 | 1.0158 | 4.03  | .560  | .476  | .413  | .364  | .325
 1.0180 |  4.18 | 1.0163 | 4.15  | .579  | .491  | .426  | .375  | .335
 1.0185 |  4.30 | 1.0168 | 4.28  | .596  | .506  | .440  | .387  | .346
 1.0190 |  4.43 | 1.0173 | 4.40  | .614  | .521  | .452  | .399  | .356
 1.0195 |  4.56 | 1.0178 | 4.53  | .632  | .537  | .466  | .410  | .367
        |       |        |       |       |       |       |       |
 1.0200 |  4.68 | 1.0182 | 4.63  | .649  | .551  | .478  | .421  | .377
 1.0205 |  4.81 | 1.0188 | 4.77  | .667  | .566  | .491  | .433  | .387
 1.0210 |  4.93 | 1.0192 | 4.87  | .684  | .581  | .504  | .444  | .398
 1.0215 |  5.05 | 1.0196 | 4.97  | .701  | .596  | .517  | .456  | .407
 1.0220 |  5.17 | 1.0201 | 5.10  | .718  | .610  | .529  | .467  | .417
        |       |        |       |       |       |       |       |
 1.0225 |  5.30 | 1.0206 | 5.22  | .737  | .625  | .543  | .479  | .428
 1.0230 |  5.43 | 1.0211 | 5.35  | .755  | .641  | .556  | .490  | .438
 1.0235 |  5.55 | 1.0216 | 5.47  | .772  | .656  | .569  | .502  | .448
 1.0240 |  5.67 | 1.0220 | 5.57  | .789  | .671  | .582  | .513  | .459
 1.0245 |  5.80 | 1.0226 | 5.72  | .808  | .686  | .595  | .525  | .469
        |       |        |       |       |       |       |       |
 1.0250 |  5.92 | 1.0230 | 5.82  | .825  | .701  | .608  | .536  | .479
 1.0255 |  6.04 | 1.0235 | 5.94  | .842  | .715  | .620  | .547  | .489
 1.0260 |  6.16 | 1.0240 | 6.07  | .859  | .729  | .633  | .558  | .499
 1.0265 |  6.28 | 1.0244 | 6.17  | .876  | .744  | .646  | .569  | .509
 1.0270 |  6.40 | 1.0249 | 6.29  | .894  | .759  | .658  | .580  | .519
        |       |        |       |       |       |       |       |
 1.0275 |  6.53 | 1.0254 | 6.43  | .912  | .775  | .672  | .592  | .529
 1.0280 |  6.65 | 1.0258 | 6.53  | .930  | .789  | .685  | .604  | .539
 1.0285 |  6.77 | 1.0263 | 6.65  | .947  | .804  | .697  | .615  | .549
 1.0290 |  6.90 | 1.0268 | 6.78  | .965  | .819  | .711  | .626  | .560
 1.0295 |  7.02 | 1.0273 | 6.90  | .983  | .834  | .724  | .638  | .570
        |       |        |       |       |       |       |       |
 1.0300 |  7.14 | 1.0278 | 7.03  | 1.000 | .849  | .737  | .649  | .580
 1.0305 |  7.26 | 1.0282 | 7.13  | 1.017 | .864  | .749  | .660  | .590
 1.0310 |  7.38 | 1.0287 | 7.23  | 1.035 | .878  | .762  | .672  | .600
 1.0315 |  7.50 | 1.0292 | 7.35  | 1.052 | .893  | .775  | .683  | .610
 1.0320 |  7.63 | 1.0296 | 7.45  | 1.071 | .908  | .788  | .695  | .621
        |       |        |       |       |       |       |       |
 1.0325 |  7.75 | 1.0301 | 7.58  | 1.088 | .924  | .802  | .706  | .631
 1.0330 |  7.88 | 1.0306 | 7.70  | 1.107 | .939  | .815  | .718  | .642
 1.0335 |  8.00 | 1.0310 | 7.80  | 1.124 | .954  | .828  | .730  | .652
 1.0340 |  8.12 | 1.0315 | 7.93  | 1.142 | .970  | .842  | .742  | .663
 1.0345 |  8.25 | 1.0320 | 8.05  | 1.160 | .985  | .855  | .753  | .673
        |       |        |       |       |       |       |       |
 1.0350 |  8.37 | 1.0325 | 8.16  | 1.178 | 1.000 | .868  | .765  | .684
 1.0355 |  8.50 | 1.0330 | 8.27  | 1.197 | 1.016 | .882  | .777  | .695
 1.0360 |  8.62 | 1.0334 | 8.37  | 1.214 | 1.031 | .895  | .788  | .705
 1.0365 |  8.74 | 1.0339 | 8.50  | 1.232 | 1.046 | .907  | .800  | .715
 1.0370 |  8.86 | 1.0344 | 8.63  | 1.249 | 1.061 | .920  | .811  | .725
        |       |        |       |       |       |       |       |
 1.0375 |  8.98 | 1.0349 | 8.75  | 1.267 | 1.076 | .933  | .823  | .735
 1.0380 |  9.10 | 1.0353 | 8.85  | 1.284 | 1.091 | .947  | .834  | .746
 1.0385 |  9.23 | 1.0358 | 8.97  | 1.303 | 1.106 | .960  | .846  | .756
 1.0390 |  9.35 | 1.0363 | 9.07  | 1.321 | 1.122 | .974  | .858  | .767
 1.0395 |  9.48 | 1.0368 | 9.20  | 1.340 | 1.138 | .987  | .870  | .778
        |       |        |       |       |       |       |       |
 1.0400 |  9.60 | 1.0372 | 9.30  | 1.358 | 1.153 | 1.000 | .881  | .788
 1.0405 |  9.73 | 1.0378 | 9.45  | 1.377 | 1.168 | 1.014 | .893  | .799
 1.0410 |  9.85 | 1.0383 | 9.57  | 1.394 | 1.184 | 1.027 | .905  | .809
 1.0415 |  9.97 | 1.0387 | 9.67  | 1.412 | 1.199 | 1.041 | .917  | .820
 1.0420 | 10.10 | 1.0393 | 9.80  | 1.431 | 1.215 | 1.054 | .929  | .830
        |       |        |       |       |       |       |       |
 1.0425 | 10.22 | 1.0397 | 9.90  | 1.449 | 1.230 | 1.067 | .941  | .841
 1.0430 | 10.35 | 1.0402 | 10.03 | 1.468 | 1.246 | 1.081 | .953  | .851
 1.0435 | 10.47 | 1.0406 | 10.13 | 1.486 | 1.261 | 1.094 | .964  | .862
 1.0440 | 10.60 | 1.0411 | 10.25 | 1.505 | 1.277 | 1.108 | .976  | .873
 1.0445 | 10.72 | 1.0416 | 10.36 | 1.523 | 1.293 | 1.122 | .988  | .884
        |       |        |       |       |       |       |       |
 1.0450 | 10.84 | 1.0420 | 10.45 | 1.540 | 1.308 | 1.135 | 1.000 | .894
 1.0455 | 10.96 | 1.0425 | 10.57 | 1.558 | 1.322 | 1.148 | 1.012 | .904
 1.0460 | 11.08 | 1.0429 | 10.67 | 1.576 | 1.338 | 1.161 | 1.023 | .915
 1.0465 | 11.20 | 1.0435 | 10.83 | 1.594 | 1.353 | 1.174 | 1.035 | .925
 1.0470 | 11.33 | 1.0440 | 10.93 | 1.613 | 1.369 | 1.188 | 1.047 | .936
        |       |        |       |       |       |       |       |
 1.0475 | 11.45 | 1.0445 | 11.05 | 1.631 | 1.384 | 1.201 | 1.059 | .946
 1.0480 | 11.57 | 1.0449 | 11.15 | 1.649 | 1.400 | 1.215 | 1.071 | .957
 1.0485 | 11.70 | 1.0454 | 11.27 | 1.668 | 1.416 | 1.229 | 1.083 | .968
 1.0490 | 11.82 | 1.0459 | 11.40 | 1.686 | 1.432 | 1.243 | 1.095 | .979
 1.0495 | 11.95 | 1.0465 | 11.53 | 1.705 | 1.449 | 1.256 | 1.107 | .990
        |       |        |       |       |       |       |       |
 1.0500 | 12.07 | 1.0468 | 11.60 | 1.724 | 1.464 | 1.270 | 1.119 | 1.00
 1.0505 | 12.20 | 1.0474 | 11.75 | 1.743 | 1.479 | 1.284 | 1.131 | 1.01
 1.0510 | 12.32 | 1.0478 | 11.84 | 1.761 | 1.495 | 1.298 | 1.144 | 1.02
 1.0515 | 12.45 | 1.0482 | 11.93 | 1.780 | 1.511 | 1.311 | 1.156 | 1.03
 1.0520 | 12.57 | 1.0488 | 12.07 | 1.797 | 1.526 | 1.325 | 1.167 | 1.04
        |       |        |       |       |       |       |       |
 1.0525 | 12.69 | 1.0492 | 12.17 | 1.816 | 1.542 | 1.338 | 1.179 | 1.05
 1.0530 | 12.81 | 1.0497 | 12.30 | 1.834 | 1.557 | 1.351 | 1.191 | 1.06
 1.0535 | 12.93 | 1.0502 | 12.40 | 1.852 | 1.572 | 1.364 | 1.203 | 1.07
 1.0540 | 13.05 | 1.0506 | 12.50 | 1.870 | 1.588 | 1.378 | 1.215 | 1.08
 1.0545 | 13.18 | 1.0512 | 12.65 | 1.890 | 1.604 | 1.392 | 1.227 | 1.09
        |       |        |       |       |       |       |       |
 1.0550 | 13.30 | 1.0516 | 12.74 | 1.908 | 1.620 | 1.405 | 1.239 | 1.10
 1.0555 | 13.42 | 1.0520 | 12.83 | 1.926 | 1.635 | 1.419 | 1.250 | 1.11
 1.0560 | 13.55 | 1.0525 | 12.95 | 1.945 | 1.651 | 1.433 | 1.263 | 1.12
 1.0565 | 13.67 | 1.0529 | 13.05 | 1.964 | 1.667 | 1.447 | 1.275 | 1.14
 1.0570 | 13.80 | 1.0534 | 13.16 | 1.983 | 1.684 | 1.461 | 1.288 | 1.15
--------+-------+--------+-------+-------+-------+-------+-------+-----


TABLE 10.—_Specific Gravity and Solids of Tomato Pulp_[20]

        =========+==========
        Specific | Per cent
         gravity |  solids
        at 68° F.|_in vacuo_
                 |at 70° C.
        ---------+----------
         1.0145  |   3.30
         1.0150  |   3.42
         1.0155  |   3.55
         1.0160  |   3.67
         1.0165  |   3.80
                 |
         1.0170  |   3.92
         1.0175  |   4.05
         1.0180  |   4.18
         1.0185  |   4.30
         1.0190  |   4.43
                 |
         1.0195  |   4.56
         1.0200  |   4.68
         1.0205  |   4.81
         1.0210  |   4.93
         1.0215  |   5.05
                 |
         1.0220  |   5.17
         1.0225  |   5.30
         1.0230  |   5.43
         1.0235  |   5.55
         1.0240  |   5.67
                 |
         1.0245  |   5.80
         1.0250  |   5.92
         1.0255  |   6.04
         1.0260  |   6.16
         1.0265  |   6.28
                 |
         1.0270  |   6.40
         1.0275  |   6.53
         1.0280  |   6.65
         1.0285  |   6.77
         1.0290  |   6.90
                 |
         1.0295  |   7.02
         1.0300  |   7.14
         1.0305  |   7.26
         1.0310  |   7.38
         1.0315  |   7.50
                 |
         1.0320  |   7.63
         1.0325  |   7.75
         1.0330  |   7.88
         1.0335  |   8.00
         1.0340  |   8.12
                 |
         1.0345  |   8.25
         1.0350  |   8.37
         1.0355  |   8.50
         1.0360  |   8.62
         1.0365  |   8.74
                 |
         1.0370  |   8.86
         1.0375  |   8.98
         1.0380  |   9.10
         1.0385  |   9.23
         1.0390  |   9.35
                 |
         1.0395  |   9.48
         1.0400  |   9.60
         1.0405  |   9.73
         1.0410  |   9.85
         1.0415  |   9.97
                 |
         1.0420  |  10.10
         1.0425  |  10.22
         1.0430  |  10.35
         1.0435  |  10.47
         1.0440  |  10.60
                 |
         1.0445  |  10.72
         1.0450  |  10.84
         1.0455  |  10.96
         1.0460  |  11.08
         1.0465  |  11.20
                 |
         1.0470  |  11.33
         1.0475  |  11.45
         1.0480  |  11.57
         1.0485  |  11.70
         1.0490  |  11.82
                 |
         1.0495  |  11.95
         1.0500  |  12.07
         1.0505  |  12.20
         1.0510  |  12.32
         1.0515  |  12.45
                 |
         1.0520  |  12.57
         1.0525  |  12.69
         1.0530  |  12.81
         1.0535  |  12.93
         1.0540  |  13.05
                 |
         1.0545  |  13.18
         1.0550  |  13.30
         1.0555  |  13.42
         1.0560  |  13.55
         1.0565  |  13.67
                 |
         1.0570  |  13.80
         1.0575  |  13.92
         1.0580  |  14.05
         1.0585  |  14.17
         1.0590  |  14.29
                 |
         1.0595  |  14.42
         1.0600  |  14.54
         1.0605  |  14.67
         1.0610  |  14.79
         1.0620  |  15.03
                 |
         1.0630  |  15.27
         1.0640  |  15.52
         1.0650  |  15.77
         1.0660  |  16.02
         1.0670  |  16.27
                 |
         1.0680  |  16.52
         1.0690  |  16.77
         1.0700  |  17.02
         1.0710  |  17.27
         1.0720  |  17.51
                 |
         1.0730  |  17.76
         1.0740  |  18.00
         1.0750  |  18.25
         1.0760  |  18.50
         1.0770  |  18.75
                 |
         1.0780  |  18.99
         1.0790  |  19.24
         1.0800  |  19.48
         1.0810  |  19.72
         1.0820  |  19.97
                 |
         1.0830  |  20.22
         1.0840  |  20.47
         1.0850  |  20.72
         1.0860  |  20.96
         1.0870  |  21.21
                 |
         1.0880  |  21.46
         1.0890  |  21.70
         1.0900  |  21.95
         1.0910  |  22.20
         1.0920  |  22.45
                 |
         1.0930  |  22.70
         1.0940  |  22.94
         1.0950  |  23.18
         1.0960  |  23.43
         1.0970  |  23.68
                 |
         1.0980  |  23.93
         1.0990  |  24.18
         1.1000  |  24.43
         1.1010  |  24.67
         1.1020  |  24.92
                 |
         1.1030  |  25.18
         1.1040  |  25.42
         1.1050  |  25.67
         1.1060  |  25.91
         1.1070  |  26.16
        ---------+----------
[20] This table gives the per cent of total solids contained by pulp
of different specific gravities varying from unconcentrated pulp as it
comes from the cyclone to the highly concentrated product.

 Illustration: Suppose that when the cyclone juice is all added to the
 tank the contents of which are vigorously boiling so that they are
 doubtless of uniform composition, the volume is found by the gauge
 stick to be 815 gallons. A sample of this partially evaporated pulp
 is withdrawn and filtered and the filtrate is found to have a Brix
 reading of 6.90. Let us suppose that the product is to be evaporated
 to a pulp having a specific gravity of 1.035 and the operator desires
 to know at what point to turn off the steam. By referring to Table 9
 in the column headed by the figure 1.035, we find opposite the Brix
 reading 6.90 the factor .834. Multiplying the volume of the pulp (815
 gallons) by this factor, we obtain 680 gallons. It follows, therefore,
 that the steam should be turned off when the evaporation has reached
 such a point that the gauge stick shows the volume of pulp to be 680
 gallons.

Table 9 may be used in the same way for calculating the volume of any
pulp, hot or cold, of any specified specific gravity equivalent to
a certain volume of pulp of any other stated specific gravity when
held at the same temperature. For instance, the illustration given
above serves equally well to illustrate how the relative value of two
finished pulps of different specific gravities may be calculated. It
also shows directly the relative value (based on tomato solids alone)
of the same volume of two pulps of different gravity.

 Illustration: Suppose a shipment contains 1,000 cases of No. 10 cans
 of pulp thought to have a specific gravity of 1.040 but found on
 examination to have a specific gravity of 1.0365. What is the value of
 the pulp in comparison with pulp of specific gravity of 1.040? Turning
 in Table 9 to the figure 1.0365 in the left-hand column we follow
 the horizontal line containing that figure to the column headed by
 specific gravity 1.040. Here we find that .907 is the factor by which
 to multiply the volume of pulp of a specific gravity 1.0365 to obtain
 the equivalent volume of pulp of specific gravity 1.040. The answer to
 our question therefore is 1000 × .907 = 907. In other words pulp of a
 gravity of 1.0365 judged by the tomato solids it contains, has 90.7
 per cent of the value of pulp of the gravity of 1.040.

Table 9 is based on the results obtained from a series of samples
of whole tomato pulp and cyclone juice varying in specific gravity
from 1.02 to 1.05. The table was extended by calculation to give
corresponding values for more dilute cyclone juices and more
concentrated products. The lower portion of the table has been
repeatedly confirmed by results obtained in the examination of cyclone
juice and pulp, but the figures in the higher portion of the table are
based on calculation from lower concentrations.

This table is only applicable to pulp to which no other substance, such
as salt, has been added. Salt if present to the extent of more than
0.25 per cent can be recognized by the taste. The amount of salt, when
any has been added, may be determined by the method given on page 33
and the specific gravity corrected by subtracting from the apparent
specific gravity 0.007 for each per cent of salt present. This gives
the specific gravity of the salt-free pulp and the corresponding per
cent of solids may be obtained from Table 9.




TOMATO KETCHUP


Ketchup is defined in the Federal food standards as the clean, sound
product made from properly prepared pulp of clean, sound, fresh, ripe
tomatoes, with spices, and with or without sugar and vinegar.

The solid matter, or total solids, in ketchup varies from less than 12
per cent to over 37 per cent. This means that the product varies from
a substance having barely sufficient tomato added to give color and
taste, to a rich, heavy tomato ketchup. The variation of total solids
in any one brand is, of course, less, but large differences are not
unusual. Three bottles of one brand showed a solids content varying
from 12 per cent to 16 per cent, and seven of another brand varied from
32 per cent to 37.2 per cent.

The amount of solids in a non-preservative ketchup should be not
materially less than 28 per cent. It is necessary to have a rather high
solid content for ketchup of this kind, so that it may keep after being
opened on the consumer’s table.

The variation in the insoluble solids is comparable to that in the
total solids. The values for a number of samples examined in this
laboratory ranged from .9 per cent to 2.3 per cent. As the insoluble
solids come from the tomato pulp the amount of insoluble solids is to
that extent an indication of the amount of tomato pulp used in the
manufacture of the ketchup from whole tomato pulp. The consistency of
the ketchup is dependent chiefly on the amount of insoluble tomato
solids present.

The ash usually varies from 2 per cent to 4 per cent, owing to the
different amounts of salt, which varies in general from 1½ to 3 per
cent.

The acidity ranges from .4 to 2.3 per cent. The acidity is one of the
most important factors in preventing the growth of bacteria and yeasts
in the ketchup after being opened. In order to secure the best results
the ketchup should have an acidity of over 1 per cent (expressed as
acetic acid) and an acidity of 1.25 per cent or higher adds to the
keeping quality of the ketchup after the bottle is opened. An increase
in acidity will necessarily require an increase in the amount of sugar
in order to secure the proper flavor; or, vice versa, an increase in
the sugar will necessitate an increase in acidity. In some ketchups
about one-half of the acidity is due to the citric acid of the tomatoes
and the remainder to the vinegar added in manufacture. With ketchups of
exceptionally high acidity, the proportion of citric acid to total acid
may be much less than this. There may be considerable difference in the
acidity in ketchup of the same brand due to variations in manufacture.

The sugar present in the ketchup is derived both from the pulp and
from the added sugar. In ketchup ranging from 12 to 30 per cent total
solids, from 9 to 22 per cent of the solids may consist of sugars.


METHODS OF MANUFACTURE

Ketchup may be prepared either from the fresh tomatoes, or from pulp.
The most common practice is to prepare it from fresh tomatoes, although
some manufacturers prefer to make ketchup during the winter, when they
are not so busy with other products, and therefore use pulp. Presuming
that the same quality of stock is used and the same care used in
manufacture, there are some advantages in making ketchup from fresh
tomatoes. The pulp loses some of its color by bleaching, and a ketchup
made from pulp is naturally subjected to more heating than that made
from fresh tomatoes.

In the manufacture of ketchup the fresh tomatoes may be broken by
steam or by the use of a mechanical breaker. Both methods have their
advantages, some preferring the one method, some the other.

In securing good quality in ketchup the same factors must be considered
as in the making of pulp. These factors are care in manufacture and the
use of a raw product of good color and quality. For discussion of these
points in regard to pulp, see page 7.

The constituents used in the manufacture of ketchup in addition to
the tomatoes are sugar, vinegar, salt, onions and spices. The sugar
generally used is granulated cane or beet sugar. Some of the lower
grades of cane sugar may be used satisfactorily. The terms used to
designate grades of sugar below granulated do not always give a correct
idea of the purity of the sugar and in buying such grades it is best to
have samples submitted and have analyses made for sugar content.

The vinegar generally used is 100-grain distilled vinegar.

The salt used is of the grade known as dairy salt.

A variety of spices is used in the manufacture of ketchup. Among these
are cinnamon, cassia, cloves, all-spice, pepper, cayenne pepper,
ginger, mustard and paprika. Spices may be used either in the form
of whole spices, ground spices or volatile spice oils. Whole spices
are thought by some to produce a better flavor. Ground spices, when
used, should be secured from a reputable manufacturer, as there is a
possibility of adulteration or use of low-grade material in ground
products. Volatile spice oils are used to some extent, especially of
spices containing large amounts of tannin, where there is liability
of discoloration due to the formation of iron tannate during the
manufacture of the ketchup. Acetic acid extracts of spices are also
used to a limited extent.

The sugar may be added at any time during the making of the ketchup,
but is preferably added during the latter part of the cooking. There
is less danger of scorching if added at this time. It should be added
gradually and scattered over the surface of the cooking ketchup so that
it may go into solution more readily.

Vinegar is always added a few minutes before finishing. The acetic acid
of the vinegar is volatile, and a large portion of it will be driven
off with steam if added at the beginning of the cooking.

Salt may be added at any time during the cooking, but it is best to add
it sufficiently soon so that it will be dissolved and thoroughly mixed
with the product.

The onions should be added chopped at the beginning of the cook.

Spices, either whole or ground, are generally placed in a bag and added
at the beginning of the cook. If the volatile oils are used, they
should be added shortly before finishing the ketchup, as otherwise a
large amount of them may be carried off with the steam.


FACTORY CONTROL OF THE COMPOSITION OF KETCHUP

Ketchup of uniform color, consistency and taste can be produced only by
controlling the quality and quantity of its constituents. Therefore,
any satisfactory method of control necessitates the determination of
the solids in the batch of cyclone juice before sugar, salt, vinegar
and spices are added. Control, based solely on uniform specific gravity
of the finished product, assures only that the specific gravity is
uniform; it does not assure uniformity in consistency, sweetness,
acidity, or in any other characteristic of the product.

Since, under any specific procedure in a factory, the distinctive
tomato flavor and the consistency of the finished product depend
entirely on the tomato solids, and since about half the final acidity
and sugar content is derived from the same source, the control of the
tomato solid content is especially important.

Fortunately the solids in cyclone juice have a fairly uniform
composition. The ratio of total solids to insoluble solids is fairly
constant, likewise the ratio of sugar to acid. The sugar in cyclone
juice varies from about 42 per cent to 54 per cent of the total solids,
averaging about 50 per cent.

As the consistency or body of ketchup is due chiefly to the tomato
solids, the amount of evaporation necessary to secure ketchup of the
desired consistency from a known volume of pulp measured at the boiling
temperature and of known Brix or specific gravity can be determined
from Table 9, page 56. For instance, if the volume of the boiling
pulp is 800 gallons and the corrected Brix reading of the filtrate is
5.10, it is found from Table 9 that it will be necessary to evaporate
to 423 gallons to secure a ketchup of approximately the consistency
of 1.040 pulp, to 374 gallons for a consistency comparable to 1.045
pulp and to 334 gallons for a consistency comparable to 1.050 pulp.
This evaporation is carried out, of course, with the addition of the
necessary ingredients for the making of ketchup. The amount of these
ingredients can be varied in order to secure ketchup of the desired
flavor.

After having once decided on the amount of ingredients to be used, the
manufacture may be standardized. Supposing for instance on evaporating
800 gallons of partly concentrated pulp of Brix of filtrate (5.10)
to approximately 334 gallons (calculated from the 1.050 column in
Table 9) it has been found that the use of 301 pounds of sugar, 26.7
gallons of 100 grain vinegar, 66.8 pounds of salt and 50.2 pounds
of onions together with spices gives ketchup of the flavor desired.
Dividing the amount of each ingredient by 334, it is found that each
gallon of finished ketchup contains .9 pound of added sugar, .2 pound
of salt, .15 pound of onions, and about 10 ounces of vinegar. After
having determined the amount of each ingredient per gallon of finished
ketchup, it is easy to make a table giving the amount of ingredients
necessary for a given volume of cyclone juice or concentrated pulp of
any gravity. In Table 11 such calculations are made. This table is
based on securing a ketchup having the consistency of 1.050 pulp and
starting with 800 gallons of boiling pulp of specific gravity 1.0220
(Brix reading of filtrate 5.10). Some manufacturers may desire to base
the amount of ingredients on 100 gallons or multiple of 100 gallons of
finished ketchup. This may be done by first making out a table similar
to 9 and then calculating the amount of pulp and other ingredients for
100 gallons of ketchup. This would, however, involve considerable work
as unless the pulp used had a constant specific gravity, a calculation
of the quantity of each ingredient would have to be made for the volume
of pulp for each batch.

TABLE 11.—_Manufacture of Ketchup. Quantity of Constituents to be Added
to 800 Gallons of Boiling, Partly Concentrated Pulp_

=========+==================+=========+===============================
         |Filtrate from pulp|         |      Added constituents
Specific +-------+----------+Volume of+------+---------+-------+------
 gravity |Degrees| Specific |finished |      |100-grain|       |
 of pulp |Brix at| gravity  | ketchup |Sugar | vinegar | Salt  |Onions
at 68° F.|68° F. |at 68° F. |         |      |         |       |
---------+-------+----------+---------+------+---------+-------+------
         |       |          | _Gals._ |_Lbs._| _Gals._ | _Lbs._|_Lbs._
 1.0154  | 3.50  |  1.0137  |  226.0  | 203  |  18.1   |  45.2 | 33.0
 1.0158  | 3.60  |  1.0141  |  232.0  | 209  |  18.5   |  46.4 | 34.8
 1.0162  | 3.70  |  1.0145  |  239.0  | 215  |  19.1   |  47.8 | 35.9
 1.0166  | 3.80  |  1.0149  |  245.0  | 221  |  19.6   |  49.0 | 36.8
 1.0170  | 3.90  |  1.0153  |  252.0  | 227  |  20.2   |  50.2 | 37.8
         |       |          |         |      |         |       |
 1.0174  | 4.00  |  1.0157  |  258.0  | 232  |  20.6   |  51.8 | 38.7
 1.0178  | 4.10  |  1.0161  |  265.0  | 239  |  21.2   |  53.0 | 39.8
 1.0182  | 4.20  |  1.0165  |  272.0  | 245  |  21.7   |  54.4 | 40.8
 1.0186  | 4.30  |  1.0169  |  278.0  | 250  |  22.2   |  55.6 | 41.7
 1.0190  | 4.40  |  1.0173  |  285.0  | 257  |  22.8   |  57.0 | 42.8
         |       |          |         |      |         |       |
 1.0194  | 4.50  |  1.0177  |  292.0  | 263  |  23.4   |  58.4 | 43.8
 1.0199  | 4.60  |  1.0181  |  299.0  | 269  |  23.9   |  59.8 | 44.9
 1.0202  | 4.70  |  1.0185  |  306.0  | 275  |  24.5   |  61.2 | 45.9
 1.0206  | 4.80  |  1.0189  |  313.0  | 282  |  25.0   |  62.6 | 47.0
 1.0211  | 4.90  |  1.0193  |  320.0  | 288  |  25.6   |  64.0 | 48.0
         |       |          |         |      |         |       |
 1.0216  | 5.00  |  1.0197  |  327.0  | 294  |  26.2   |  65.4 | 49.1
 1.0220  | 5.10  |  1.0201  |  334.0  | 301  |  26.7   |  66.8 | 50.2
 1.0224  | 5.20  |  1.0205  |  341.0  | 307  |  27.3   |  68.2 | 51.2
 1.0228  | 5.30  |  1.0209  |  347.0  | 312  |  27.8   |  69.4 | 52.1
 1.0232  | 5.40  |  1.0213  |  354.0  | 319  |  28.3   |  70.8 | 53.2
         |       |          |         |      |         |       |
 1.0236  | 5.50  |  1.0217  |  361.0  | 324  |  28.9   |  72.2 | 54.2
 1.0240  | 5.60  |  1.0221  |  368.0  | 331  |  29.4   |  73.6 | 55.2
 1.0244  | 5.70  |  1.0225  |  374.0  | 337  |  29.9   |  74.8 | 56.2
 1.0249  | 5.80  |  1.0229  |  381.0  | 343  |  30.5   |  76.2 | 57.2
 1.0253  | 5.90  |  1.0233  |  388.0  | 349  |  31.0   |  77.6 | 58.2
         |       |          |         |      |         |       |
 1.0257  | 6.00  |  1.0237  |  395.0  | 356  |  31.6   |  79.0 | 59.3
 1.0261  | 6.10  |  1.0241  |  402.0  | 362  |  32.1   |  80.4 | 60.4
 1.0266  | 6.20  |  1.0245  |  409.0  | 368  |  32.7   |  81.8 | 61.4
 1.0271  | 6.30  |  1.0249  |  416.0  | 374  |  33.3   |  83.2 | 62.5
 1.0275  | 6.40  |  1.0253  |  422.0  | 380  |  33.8   |  84.4 | 63.4
         |       |          |         |      |         |       |
 1.0279  | 6.50  |  1.0257  |  429.0  | 386  |  34.3   |  85.8 | 64.4
 1.0283  | 6.60  |  1.0261  |  436.0  | 392  |  34.9   |  87.2 | 65.4
 1.0287  | 6.70  |  1.0265  |  443.0  | 399  |  35.4   |  88.6 | 66.5
 1.0291  | 6.80  |  1.0270  |  450.0  | 405  |  36.0   |  90.0 | 67.5
 1.0295  | 6.90  |  1.0274  |  457.0  | 411  |  36.6   |  91.4 | 68.6
         |       |          |         |      |         |       |
 1.0299  | 7.00  |  1.0278  |  464.0  | 418  |  37.1   |  92.8 | 69.6
 1.0304  | 7.10  |  1.0282  |  471.0  | 424  |  37.7   |  94.2 | 70.7
 1.0309  | 7.20  |  1.0286  |  478.0  | 430  |  38.2   |  95.7 | 71.8
 1.0313  | 7.30  |  1.0290  |  485.0  | 437  |  38.8   |  97.1 | 72.8
 1.0318  | 7.40  |  1.0294  |  492.0  | 443  |  39.4   |  98.5 | 73.8
         |       |          |         |      |         |       |
 1.0322  | 7.50  |  1.0298  |  499.0  | 449  |  39.9   |  99.9 | 74.9
 1.0326  | 7.60  |  1.0302  |  506.0  | 455  |  40.5   | 101.3 | 76.0
 1.0330  | 7.70  |  1.0306  |  513.0  | 462  |  41.1   | 102.7 | 77.0
 1.0335  | 7.80  |  1.0310  |  521.0  | 469  |  41.7   | 104.2 | 78.2
 1.0339  | 7.90  |  1.0315  |  529.0  | 476  |  42.3   | 105.8 | 79.4
         |       |          |         |      |         |       |
 1.0343  | 8.00  |  1.0319  |  536.0  | 482  |  42.9   | 107.2 | 80.4
 1.0347  | 8.10  |  1.0323  |  543.0  | 489  |  43.5   | 108.6 | 81.5
 1.0352  | 8.20  |  1.0327  |  550.0  | 495  |  44.0   | 110.0 | 82.6
 1.0356  | 8.30  |  1.0331  |  557.0  | 501  |  44.5   | 111.4 | 83.6
 1.0361  | 8.40  |  1.0335  |  564.0  | 508  |  45.1   | 112.8 | 84.7
         |       |          |         |      |         |       |
 1.0365  | 8.50  |  1.0339  |  571.0  | 514  |  45.7   | 114.2 | 85.7
 1.0369  | 8.60  |  1.0343  |  578.0  | 520  |  46.2   | 115.6 | 86.8
 1.0374  | 8.70  |  1.0348  |  585.0  | 527  |  46.8   | 117.0 | 87.8
 1.0379  | 8.80  |  1.0352  |  592.0  | 533  |  47.4   | 118.4 | 88.8
 1.0383  | 8.90  |  1.0356  |  600.0  | 540  |  48.0   | 119.0 | 90.0
---------+-------+----------+---------+------+---------+-------+------

The use of Table 11 gives a ketchup of medium concentration. Using this
as a basis the manufacturer can decide the extent to which he should
evaporate to secure a ketchup of the consistency desired and modify the
table accordingly.

Final concentration of the ketchup is controlled in the same manner as
for pulp, either by a gauged tank or by specific gravity determination.
If we start, therefore, with a given volume of partially concentrated
cyclone juice and determine the solids present, we can in every case
quickly ascertain from the appropriate table the number of gallons of
finished product we should obtain, and the gauge stick or attached
gauge glass will indicate when to stop evaporation in the tank. One
advantage of measuring the original volume at the boiling temperature
is that no temperature corrections are necessary, as both the initial
and final temperature measurements are approximately the same.

The final concentration may be controlled, as stated above, by
determining the specific gravity of the finished product by one of the
methods given under pulp (see page 33 and following). The determination
of specific gravity at this point will probably give more accurate
results than the use of a gauge stick, and is to be recommended for
use with the finished product, provided the added constituents have
been standardized. The method described on page 42 for determining the
specific gravity of hot tomato pulp, may be used for obtaining the
per cent of solids in the boiling cyclone juice in place of the Brix
spindle reading on the filtrate.

Table 11 for controlling the concentration of finished ketchup is
based on the idea that there shall be a definite volume of partly
concentrated pulp in the tank when the inflow of cyclone juice is
stopped and the sample is taken for analysis. In this respect, this
method of controlling the concentration of ketchup varies from the
method described on page 54 for the control of the concentration of
tomato pulp. It is sometimes convenient to secure this definite volume
by filling the tank to a greater height than is desired and evaporating
until the desired volume is secured. When this point is reached the
sample of pulp is taken for specific gravity and steam is again turned
on the tank.

The Abbé refractometer may also be used for controlling the final
concentration of the ketchup. This provides a very simple and quick
method for determining the percentage of solids. It requires but
a few drops of the filtered liquor from the ketchup to make the
determination. The reading may be taken and the calculation made in
one or two minutes’ time by use of Tables 13 and 14.

The table for calculating the solids from the refractometer reading is
Geerlig’s table for dry substance in sugar-house products, and is taken
from the Methods of the Association of Official Agricultural Chemists,
1919. The entire table is not given but only the range over which it
might possibly be desired to use it in the control of the manufacture
of ketchup.

The results by this method are only approximate, but are sufficiently
accurate for manufacturing control. Table 12 gives a comparison of the
solids obtained by drying in vacuum at 70° C. with results obtained by
the refractometer.


TABLE 12.—_Solids in Ketchup Obtained by Drying in Vacuum at 70° C. and
by Abbé Refractometer from Geerlig’s Table_

        +------------------------------+
        |   Solids in tomato ketchup   |
        +----------------+-------------+
        |  By drying in  |   By Abbé   |
        |vacuum at 70° C.|refractometer|
        +----------------+-------------+
        |   _Per cent_   | _Per cent_  |
        |      29.5      |    29.0     |
        |      30.0      |    29.4     |
        |      32.8      |    32.4     |
        |      28.0      |    27.9     |
        |      22.0      |    21.8     |
        |      27.7      |    28.0     |
        +----------------+-------------+

There are several errors in this determination which partially
compensate for each other and give results fairly comparable with
those obtained by drying. The refractometer of course determines only
soluble constituents. Since salt gives a higher refractive reading
than the same per cent of sugar, and since tomato solids give a higher
refractive reading than the same percentage of sugar, and since any
acetic acid of the vinegar is also read as solids on the refractometer,
the total increase in reading due to these different factors nearly
compensates for the insoluble solids of the ketchup.

The variation of the per cent of solids as obtained by the
refractometer from that obtained by drying will depend somewhat on
the composition of the ketchup and in using the refractometer it is
advisable to also determine the solids by drying on a few samples to
obtain the relation between the two figures for that particular ketchup.


TABLE 13.—_Refractive Index and Per Cent Solids in Tomato Ketchup_[21]

        ==========+======+===================
        Refractive| Per  |  Decimals to be
          index   | cent |     added for
                  |solids|fractional readings
        ----------+------+-------------------
          1.3484  |  11  |   0.0001 = 0.05
          1.3500  |  12  |   0.0002 = 0.1
          1.3516  |  13  |   0.0003 = 0.2
          1.3530  |  14  |   0.0004 = 0.25
          1.3546  |  15  |   0.0005 = 0.3
                  |      |
          1.3562  |  16  |   0.0006 = 0.4
          1.3578  |  17  |   0.0007 = 0.45
          1.3594  |  18  |   0.0008 = 0.5
          1.3611  |  19  |   0.0009 = 0.6
          1.3627  |  20  |   0.0010 = 0.65
                  |      |
          1.3644  |  21  |   0.0011 = 0.7
          1.3661  |  22  |   0.0012 = 0.75
          1.3678  |  23  |   0.0013 = 0.8
          1.3695  |  24  |   0.0014 = 0.85
          1.3712  |  25  |   0.0015 = 0.9
          1.3729  |  26  |   0.0016 = 0.95
                  |      |
          1.3746  |  27  |   0.0001 = 0.05
          1.3764  |  28  |   0.0002 = 0.1
          1.3782  |  29  |   0.0003 = 0.15
          1.3800  |  30  |   0.0004 = 0.2
          1.3818  |  31  |   0.0005 = 0.25
                  |      |
          1.3836  |  32  |   0.0006 = 0.3
          1.3854  |  33  |   0.0007 = 0.35
          1.3872  |  34  |   0.0008 = 0.4
          1.3890  |  35  |   0.0009 = 0.45
          1.3909  |  36  |   0.0010 = 0.5
                  |      |
          1.3928  |  37  |   0.0011 = 0.55
          1.3947  |  38  |   0.0012 = 0.6
          1.3966  |  39  |   0.0013 = 0.65
          1.3984  |  40  |   0.0014 = 0.7
          1.4003  |  41  |   0.0015 = 0.75
                  |      |   0.0016 = 0.8
                  |      |   0.0017 = 0.85
                  |      |   0.0018 = 0.9
                  |      |   0.0019 = 0.95
                  |      |   0.0020 = 1.0
                  |      |   0.0021 = 1.0
        ----------+------+-------------------

[21] Geerlig’s table for dry substance in sugar house products by Abbé
refractometer at 28°C.

In using Table 13, find the refractive index which is next lower
than the reading actually obtained and note the corresponding whole
number for the per cent of dry substance. Subtract the refractive
index obtained from the table from the observed reading; the decimal
percentages corresponding to this difference, as given in the column so
marked, is added to the whole per cent of solids as first obtained.

Correction must also be made for the temperature if above or below 28°
C. The temperature correction is obtained from Table 14. For instance,
suppose the refractive index was 1.3750 and that the temperature was
25° C. The per cent of solids as obtained from the table would be
27.2. The correction for temperature would amount to .14, which would
be added to this reading, giving 27.34 as the per cent of solids.


TABLE 14.—_Corrections for Temperature to be Used with Table 13_

        ============+=============================
                    |     Per cent of solids.
        Temperature,+----+----+----+----+----+----
            ° C.    | 10 | 15 | 20 | 25 | 30 | 40
        ------------+----+----+----+----+----+----
                    |      To be subtracted
                    +----+----+----+----+----+----
             20     |0.55|0.56|0.57|0.58|0.60|0.62
             21     | .48| .49| .50| .51| .52| .54
             22     | .42| .42| .42| .44| .45| .47
             23     | .34| .35| .36| .37| .38| .39
             24     | .27| .28| .28| .29| .30| .31
             25     | .21| .21| .22| .22| .23| .23
             26     | .13| .14| .14| .15| .15| .16
             27     | .07| .07| .07| .07| .08| .08
                    +----+----+----+----+----+----
                    |         To be added
                    +----+----+----+----+----+----
             29     |0.07|0.07|0.07|0.07|0.08|0.08
             30     | .13| .14| .14| .14| .15| .15
             31     | .21| .21| .22| .22| .23| .23
             32     | .27| .28| .28| .29| .30| .31
             33     | .34| .35| .36| .37| .38| .39
             34     | .42| .42| .43| .44| .45| .47
             35     | .48| .49| .50| .51| .52| .54
        ------------+----+----+----+----+----+----

Whether or not ketchup should be processed after filling into bottles
depends on the conditions under which it is bottled. If the bottled
product can be sealed at 180° F. or better a process is not necessary
and is an unnecessary expense and waste of time, besides it may
injure the color of the product. With the modern type of equipment
it is possible to fill the bottles at a temperature which obviates
sterilization. Care must be taken that the temperature of the ketchup
in the receiving tank feeding the filler does not fall too low. Care
must also be avoided in order not to fill the ketchup at too high a
temperature as it results in excessive shrinkage of the contents.

For ketchup filled at relatively low temperature a process should be
used. The process necessary will depend upon the temperature at which
the ketchup is filled and on the time that may elapse between filling
and processing. Sanitary conditions of the factory and equipment are
exceedingly important not only in relation to ease of sterilization but
also in securing a product of good quality.

In stacking ketchup it is best to stack the bottles upside down. This
tends to prevent darkening of the ketchup in the neck of bottle, a
condition known as “black neck.” It has been our experience that
wherever this condition has occurred it is due to leakage of air into
the bottles. Stacking bottles in this way undoubtedly keeps the cork of
the cap moist and makes the seal more effective.




CHILI SAUCE


Chili sauce is of the same general character as ketchup but is made
from peeled and cored tomatoes without removing the seeds, contains
more sugar and onions and sometimes is made hotter than ketchup by the
use of more cayenne pepper. There is a great variation among different
manufacturers with respect to the methods of treating the tomatoes.
Usually large to medium sized tomatoes are employed, separated from
the small tomatoes which are used for making pulp and ketchup. Some
manufacturers of chili sauce place the peeled and cored tomatoes
directly into the kettle and mix the other ingredients without any form
of breaking. Other manufacturers have various methods of breaking and
crushing the tomatoes. Several crushers for this purpose are on the
market and other means of breaking, such as meat choppers, meat cutters
and apple graters are employed. Some convey the tomatoes from the
peeling room to the kettle through a pump which breaks them up more or
less.

Because of the nature of the product there is no method available for
testing the concentration of chili sauce and determining the point at
which the cooking should be stopped. The refractometer may be used as
a rough method of controlling the concentration. The percentage of
solids as determined from the refractometer reading and Geerlig’s table
is too low on account of the relatively high percentage of insoluble
solids. However, a relation between the soluble solids and total
solids may be obtained in this way which may be useful in controlling
the concentration. The consistency of the product is always regulated
by its appearance. The amount of cooking varies among different
manufacturers but in general there is a concentration of from 40 to
45 per cent of the volume of the raw tomatoes employed. That is, 100
gallons of peeled and cored tomatoes yield from 40 to 45 gallons of
chili sauce.

The amount of onions added to chili sauce is substantially larger than
the amount used with ketchup. Some manufacturers use approximately
twice as much as the former. Hier[22] suggests 100 pounds of onions
when used in the preparation of 100 gallons of chili sauce. Large
onions should be used since they are more easily peeled and give less
waste than smaller onions. They should be carefully peeled and should
be finally chopped in order to safeguard against stopping up the tubes
of the filling machine.

[22] “The Manufacture of Tomato Products, 1919.”

The cooking is substantially the same as with ketchup and the same
ingredients are used with the exception of garlic which is not
employed. Some manufacturers make the product rather mild, while
others use substantially twice as much cayenne pepper as with ketchup.
The same amount of salt and vinegar are employed with ketchup but
substantially more sugar, some manufacturers using one-half more sugar
than with ketchup.

Because of its lumpy condition chili sauce affords more difficulty in
filling into the bottle than is the case with ketchup. The bottle is
also harder to seal. Its wide neck makes it more difficult to make the
sealing tight than the smaller neck ketchup bottles, and the black
rings in the top of the bottle are more frequent and more conspicuous
than is the case with ketchup.

The discussion of the processing given under ketchup (p. 70) is also
applicable to chili sauce.




PUBLICATIONS

RESEARCH LABORATORY

NATIONAL CANNERS ASSOCIATION


BULLETINS

   *1 Some Safety Measures in Canning Factories
   *2 Swells and Springers (Superseded by Circular 6-L)
   *3 Tomato Pulp (Superseded by Bulletin 21-L)
   *4 Preliminary Bulletin on Canning
   *5 The Examination of Evaporated Milk
   *6 A cause of Dark Color in Canned Corn
   *7 Specific Gravity and Solids in Tomato Pulp
      (Superseded by Bulletin 21-L)
   *8 Exhaust and Vacuum
   *9 Processing and Process Devices
  *10 Lye Peeling
   11 Deterioration in Asparagus
   12 Washing Fruits and Vegetables
   13 Washing and Cleaning Cans
  *14 Bacteriological Examination of Canned Foods
   15 Suggestions for Canning Pork and Beans
   16-L Heat Penetration in Processing Canned Foods
   17-L Relation of Processing to the Acidity of Canned Foods
   18-L Black Discoloration in Canned Corn
  *19-L Vitamins in Canned Foods
   20-L The Effect of Hard Water in Canning Vegetables


CIRCULARS

  *1-L Springers and Perforations in Canned Fruits
   2-L The Discoloration of Lye Hominy
   3-L Some Research Problems of the Canning Industry
   4-L The Effect on Canned Foods of Industrial Wastes in the Water Supply
   5-L Processing of Peas
   6-L Swells and Springers
   7-L Processing of String Beans and Beets
   8-L Processing of Corn and Pumpkin

* Out of print.


Transcriber’s notes:
In the text version, italics are represented by _underscores_, and
bold and black letter text by =equals= symbols.

Page
p16   iris diaphrams — corrected to diaphragms.
p16   Abbe condenser usually has an accent on the e
      — left as printed.
p17   Compound miscroscope — corrected to microscope
p17  There are two anchors for footnote 6
p21  Table 2 has been split into 3 sections because of its width.
p22  Table 3 has been split into 3 sections because of its width.
p23  Table 4 has been split into 2 sections because of its width.
p25  Table 5 refractometer readings column needed to be shifted
     down one row starting between 5.60 and 5.66.
p25  Table 5 The entry for specific gravity of the
     filtrate for a whole pulp reading in vacuo of 6.05 percent is given
     as 0.0235 — this has been corrected to 1.0235
p32   raw product it its — changed to it is.
p60   value of of the pulp. — extra of removed.
p68   refractometor — changed to refractometer