POPULAR EDITION.

  BULLETIN No. 183.        DECEMBER, 1900.

  New York Agricultural Experiment Station.

  GENEVA, N. Y.

  [Illustration]

  DAIRY DISAGREEABLES BUSY THE BACTERIOLOGISTS.

  F. H. HALL, H. A. HARDING, L. A. ROGERS AND G. A. SMITH.

  PUBLISHED BY THE STATION.




BOARD OF CONTROL.


     GOVERNOR THEODORE ROOSEVELT, Albany.
     STEPHEN H. HAMMOND, Geneva.
     AUSTIN C. CHASE, Syracuse.
     FRANK O. CHAMBERLAIN, Canandaigua.
     FREDERICK C. SCHRAUB, Lowville.
     NICHOLAS HALLOCK, Queens.
     LYMAN P. HAVILAND, Camden.
     EDGAR G. DUSENBURY, Portville.
     OSCAR H. HALE, North Stockholm.
     MARTIN L. ALLEN, Fayette.


OFFICERS OF THE BOARD.

     STEPHEN H. HAMMOND, _President_.
     WILLIAM O’HANLON, _Secretary and Treasurer_.


EXECUTIVE COMMITTEE.

     STEPHEN H. HAMMOND,
     MARTIN L. ALLEN,
     FRANK O. CHAMBERLAIN,
     FREDERICK C. SCHRAUB,
     LYMAN P. HAVILAND,
     NICHOLAS HALLOCK.


STATION STAFF.

     WHITMAN H. JORDAN, SC. D., _Director_.

     GEORGE W. CHURCHILL, _Agriculturist and Superintendent of Labor_.

     WILLIAM P. WHEELER, _First Assistant_ (_Animal Industry_).

     FRED C. STEWART, M.S., _Botanist_.

     LUCIUS L. VANSLYKE, PH.D., _Chemist_.

     CHRISTIAN G. JENTER, PH.C.,
  [A]WILLIAM H. ANDREWS, B.S.,
     J. ARTHUR LECLERC, B.S.,
  [B]AMASA D. COOK, PH.C.,
     FREDERICK D. FULLER, B.S.,
  [B]EDWIN B. HART, B.S.,
  [A]CHARLES W. MUDGE, B.S.,
  [A]ANDREW J. PATTEN, B.S., _Assistant Chemists_.

     HARRY A. HARDING, M.S., _Dairy Bacteriologist_.

     LORE A. ROGERS, B.S., _Assistant Bacteriologist_.

     GEORGE A. SMITH, _Dairy Expert_.

     FRANK H. HALL, B.S., _Editor and Librarian_.

     VICTOR H. LOWE, M.S.,
  [C]F. ATWOOD SIRRINE, M.S., _Entomologists_.

     PERCIVAL J. PARROTT, A.M., _Assistant Entomologist_.

     SPENCER A. BEACH, M.S., _Horticulturist_.

     HEINRICH HASSELBRING, B.S.A., _Assistant Horticulturist_.

     FRANK E. NEWTON,
     JENNIE TERWILLIGER, _Clerks and Stenographers_.

     ADIN H. HORTON, _Computer_.

Address all correspondence, not to individual members of the staff, but
to the NEW YORK AGRICULTURAL EXPERIMENT STATION, GENEVA, N. Y.

The Bulletins published by the Station will be sent free to any farmer
applying for them.




POPULAR EDITION[D]

OF

BULLETIN NO. 183.

DAIRY DISAGREEABLES BUSY THE BACTERIOLOGISTS.

F. H. HALL.


FLAVOR IN MILK AND ITS PRODUCTS.

[Sidenote: =Flavor: How tested?=]

Good flavor sells milk, cream, butter and cheese; poor flavor condemns
them. Flavor is that indescribable something, which, in good dairy
products, appeals pleasantly to our senses, but often passes unnoticed
because so familiar; in poor products it is equally indescribable, but
more often characterized in vigorous language, when “frowzy” butter,
“garlicy” milk, “bitter” cream or “strong” cheese present their
offensive odors and tastes. The ordinary consumer calls flavor the
“taste” of the article which tickles his palate; but the expert knows
that the nerves of smell play the larger part, and he depends for his
judgment largely upon a trained nose. Hence we see the butter judge
or cheese scorer pass the trier beneath his nostrils with deep-drawn
breath and meditative study of the aroma which arises. Smells, however,
cannot be measured in degrees or separated into their elements by the
spectroscope; therefore we have to depend upon general terms, often
differing with the different experts, in our discussion of flavor; yet
we have some well-marked classes which serve as a basis for reference.

[Sidenote: =Faults of flavor classified.=]

We can separate the faulty flavors into classes by their origin. The
minute particles thrown off by dairy products, whose impact upon tongue
or nostrils give rise to taste or smell, may come (1) from compounds in
the food of the cow or developed in her body (2) from matters, other
than germs, taken up by the milk while it stands in poorly-ventilated
stables or rooms reeking with foul smells, or (3) from substances which
are the direct or indirect result of the activity of living organisms
in the milk.

Odors of the first class will be most noticeable while the milk is
warm from the cow and will not increase with time. They are really
far less common than dairymen generally believe and may be avoided
almost entirely by careful feeding. Garlic, turnips, cabbage and such
“fragrant” edibles will, of course, taint the milk if they are fed
within a few hours before milking; but when fed soon after the cows are
milked, the volatile oils to which these odors are due will generally
disappear from the animal’s system before the next morning or evening.

Too often odors of the second class are assigned to the first, and
the old cow takes the blame for man’s fault; as milk very readily and
quickly takes up smells and tastes from its surroundings. When the
owner delivers milk to the factory and is told that it “smells bad,” he
forgets that he or his men let it stand in the uncleaned stable to draw
in the “cowy” and worse odors, while the cows were being fed and some
other chores attended to; or that they poured it into pails that lacked
a little of perfect sweetness; and he immediately says; “I’ve got to
stop feeding silage.” “The cows ate some cabbage trimmings last night,”
or, “Someone forgot to close the rye-field gate.”

Odors of these two classes, due to volatile compounds in the milk, are
of most importance in the milk and cream trade, as the faults largely
disappear in making butter and cheese. Thorough æration is often
helpful in the removal of such flavors.

Odors of the third class, except in some very rare cases where the
udder itself is the seat of colonies of bacteria, are not observed in
freshly-drawn milk. The bacteria, molds and yeasts which cause them
must have a chance to develop and to set up chemical changes in the
milk; and this rarely occurs to any great extent within 12 hours from
the time the milk is drawn. A high temperature, however, is favorable
to growth of these low forms of plant life; so in warm weather milk
faults are common. In butter-making, and in cheese-making, also,
the heat often used to ripen the cream and the high temperature at
which the milk is held in “setting” and “cooking” the curd, furnish
conditions very favorable to the germs present and they develop with
great rapidity. In their growth part of the milk is used for food and
in its breaking down into simpler compounds the aromatic substances
which make flavor, good or bad, are formed.

The flavor of good milk and cream, then, is an inherent quality due
to the normal constituents of the milk; the flavors of butter, both
good and bad, except that due to the fat and to odors absorbed by the
milk, are held to be the result of bacterial action; the fundamental
flavors of cheese are probably due to chemical decomposition, started
by unorganized ferments known as enzyms; joined with which are other
flavors marking the individual cheeses, which are probably due to
bacteria; and it has recently been found that in some cases yeasts have
been the cause of bad flavor.


FISHY FLAVOR IN MILK.

[Sidenote: =Ready Relief.=]

This peculiar smell, as though the milk had set in a close room with
a barrel of not-too-fresh fish, was brought to the attention of the
Bacteriologist by a dealer who had already located it as coming from
the milk of a certain dairy. The dairyman is a more than ordinarily
careful milk-handler, who gladly coöperated with the Station in efforts
to locate the trouble in his herd. Bottles were supplied by the
Bacteriologist, which had been steamed to insure the death of all germ
life and then sealed. These sealed bottles were taken by the dairyman
to his farm; at milking time each was opened long enough to receive a
little milk from each quarter of the udder of a single cow; and then
re-sealed. All were brought to the Station; and, upon examination, the
odor was found only in the milk of one cow. The owner rejected her milk
and heard no further complaint, from the dealer, of bad smells. This
was the practical point; and it was thus easily and simply gained.

[Sidenote: =Cause not found.=]

From the scientist’s standpoint, though, only a beginning had been
made; the real cause of the trouble was as yet unknown; nor was any
satisfactory solution reached even after a long investigation. The
flavor could hardly come from the food, for all the cows were fed alike
and no objectionable weeds were found in their pasture. The cow seemed
perfectly healthy and no evidence of inflammation or disease could be
found on the udder or in the milk. Neither could any form of bacteria
be found in the milk, which, in cultures or introduced into the udder
of a healthy cow, would reproduce the fishy smell.

[Sidenote: =Rare fault.=]

At least two other cases of similar flavor have been known; but no
cause was evident in either case. The trouble is very infrequent, at
worst, and is here discussed mainly to show how easily a trouble due to
one cow can be located by taking individual samples of the milk; and
how cheaply gotten rid of by leaving out the objectionable product.


BITTER FLAVOR IN NEUFCHATEL CHEESE.

[Sidenote: =An uncompleted study.=]

A little better result than that in the study of fishy flavor was
reached in the investigation of a bitter flavor in Neufchatel cheese;
but this study also had to be left incomplete. The trouble in the
factory was easily remedied; and the germ responsible for the outbreak
was obtained in pure culture; but full study of the fault in all its
bearings was hindered by the refusal of the herd owner to admit that
the trouble was due to his milk. The investigation had to stop with the
guilty herd; it did not locate the original source of infection.

[Sidenote: =Method of detection.=]

This bitter flavor is not the same as the bitterness quite common in
milk and cream at certain seasons of the year; as the milk itself
tasted and smelled all right until well along in the process of
cheese-making when the curd was being ærated and drained. The flavor
was noticed in the factory in October and could not be checked, though
the maker took great pains to wash and scald all his utensils and
everything which touched the milk after it came from the farm. To
locate the trouble, samples were taken of the milk of each patron
and the cheese-making process started with each sample. In 18 hours
all the samples of curd appeared normal but two, which were gassy
and bad-smelling; and one of these, when drained and exposed to the
air, showed a pronounced bitter flavor. This sample proved to be from
the dairy which had furnished the milk for making the Neufchatel,
a milk specially selected because of its high fat-content. This
furnished direct proof that the fault lay in the milk, not in its
factory handling; and rejection of this milk ended the trouble in the
Neufchatel. As already stated, the study could not be carried into the
herd to see whether one cow, wrong stable surroundings, a stagnant pool
of water or contaminated dairy utensils were to blame for the trouble
in the factory.

[Sidenote: =Bacteria blamable.=]

Samples of this faulty milk were taken for laboratory study and various
bacteria and molds were separated. This was done by diluting the milk
with a sterilized fluid so that the germs were quite widely separated
when the milk was poured out in flat glass dishes. Each kind of germ
is marked by some peculiarity of growth which makes it possible to
distinguish between them; and pure cultures can be made by transferring
a little of the growing colony to a new dish of sterilized agar,
gelatin or other material suited to germ life. From these pure cultures
fresh milk from the Station herd was inoculated and small Neufchatel
cheeses made. No bitter flavor was noticed in similar check cheeses;
and the milk containing only one of the forms of germ life found
produced bitter cheese. The bitterness, as in the factory, was noticed
only after the curd was drained and ærated. Soft, poorly-drained curd
was free from the flavor though well inoculated with the short bacillus
which produced the bad flavor in well-dried curd. This shows that the
germ is one which requires exposure to the air to develop the bitter
compound in the cheese. Unfortunately this germ, when cultivated in
milk for some time lost the power of producing bitter cheese, so the
investigation came to an end.


SWEET FLAVOR IN CHEDDAR CHEESE.

[Sidenote: =A new cause of cheese faults.=]

By methods similar to those just given the cause of the common and
costly cheese fault known as “sweet flavor” has probably been found.
This investigation was demanded by the occurrence in some of the
best-conducted factories of outbreaks of the trouble which most
thorough cleansing and scalding fail to overcome. It is believed that
these attacks result in annual loss to the State of at least $10,000.
The trouble is of obscure origin and is peculiar in its development,
manifesting itself in flavors of varying intensity and character, from
a faint sweetness to a well-marked fruity smell and taste, and seeming
to appear and disappear without rule or method. This made study more
difficult than in the case of well-defined troubles; but its manner of
development in the cheese indicated some living germ as the cause; so
the attempt at solution of the problem was made from that standpoint.

By cultural methods, study was made of the flora of good and poor
cheeses; that is, the various forms of plant life existing in these
cheeses were separated from each other and their forms, actions and
effects noted. These forms of life were mostly bacteria and yeasts;
and, contrary to the usual rule, it was the latter which finally seemed
to demand attention.

Yeasts are plants a little higher in the scale of life than bacteria,
a little larger but still microscopic, and differing from bacteria in
their mode of reproduction, which is by budding of a new cell from
an old one rather than by division of an old cell into two new ones
of equal size. Their most characteristic action is the formation of
alcohol and carbon dioxide; which makes them indispensable in brewing
and bread making.

In good cheeses almost no yeasts were found, but in the sweet-flavored
cheeses sometimes half of the germs present were yeasts; and they were
always found where the sweet flavor was noticed. Yeasts have not been
recognized, hitherto, as a cause for such cheese faults; but their
presence in such numbers cast strong suspicion upon them; which actual
work proved to be well founded, for pronounced cases of sweet flavor
developed in cheeses made from pure milk inoculated with the yeasts;
and the vat in which the cheese was made became contaminated so that,
without further intentional inoculation, sweet-flavored cheese was
produced where none had been known before. As yeasts have hitherto
played minor parts in dairy investigations, no classification of those
found has yet been made, nor has the exact flavor due to each one been
determined. Further study is being given to the subject.


RUSTY SPOT IN CHEDDAR CHEESE.

[Sidenote: =Not a flavor.=]

Rusty spot is not a flavor trouble, as spotted cheeses of this kind
may be all right in taste and smell. The spots, however, are offensive
to the eye and render the cheese salable only at a reduction in price,
if at all. From the Station investigations, continued for nearly two
years, along much the same lines as the flavor studies but with a
little more definite guide in color than in taste and smell, some
direct knowledge has been gained, though not as definite as could be
desired along preventive and remedial lines.

[Sidenote: =Cause and conditions.=]

The rusty spots are colonies of minute plants, bacteria, growing on
the walls of the air spaces within the cheese. The trouble usually
appears in May, often does little harm during the middle of the summer
and generally disappears in October. In cheese made with a high acid
content the moisture content of the air spaces within the cheese is
low, and without abundance of moisture the germs make little growth;
hence the spots are too small to be noticed. The marked influence, on
the germs of rusty spot, of this slight variation in the character
of the cheese probably accounts for the unexpected appearance and
disappearance of the spots from cheeses of an occasional day’s make in
infected factories.

[Sidenote: =Cure.=]

Where the spots are not too large or too plentiful, giving the cheese a
good high color covers up the rustiness so that it is not noticeable.
To get entirely rid of the trouble has bothered some of the best
cheese-makers, aided by good advisers; but plenty of hot water followed
by a liberal use of live steam on vats, cans and working utensils
should give good results.




FOOTNOTES:


[A] Connected with Fertilizer Control.

[B] At Second Judicial Department Branch Station, Jamaica, N. Y.

[C] Absent on leave.

[D] This is a brief review of Bulletin No. 183 of this Station entitled
Notes on Some Dairy Troubles, by H. A. Harding, L. A. Rogers and G.
A. Smith. Anyone specially interested in the detailed account of the
investigations will be furnished, on application, with a copy of the
complete bulletin. The names of those who so request will be placed
on the Station mailing list to receive future bulletins, popular or
complete as desired. Bulletins are issued at irregular intervals as
investigations are completed, not monthly.




TRANSCRIBER’S NOTES:


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