MILK.
Milk, as the first and natural food of man, has been used from the
remotest antiquity of the human race. It is produced by the females of
that class of animals known as the _mammalia_, and was designed by
nature as the nourishment of their young; but the richest and most
abundant secretions in common use are those of the cow, the camel, the
mare, and the goat. The use of camel’s milk is confined chiefly to
Africa and to China, that of mares to Tartary and Siberia, and that of
goats to Italy and Spain. The milk of the cow is universally esteemed.
Milk is an opaque fluid, generally white in color, having a sweet and
agreeable taste, and is composed of a fatty substance, which forms
butter, a caseous substance, which forms cheese, and a watery residuum,
known as serum, or whey, in cheese-making. The fatty or butyraceous
matter in pure milk varies usually from two and a half to six and a half
per cent.; the caseous or cheesy matter, from three to ten per cent.;
and the serous matter, or whey, from eighty to ninety per cent.
To the naked eye milk appears to be of the same character and
consistence throughout; but under the microscope a myriad of little
globules of varied forms, but mostly round or ovoid, and of very unequal
sizes, appear to float in the watery matter. On more minute
examination, these butter-globules are seen to be enclosed in a thin
film of caseous matter. They are so minute that they filter through the
finest paper. Milk readily assimilates with water and other sweet and
unfermented liquids, though it weighs four per cent. more than water.
Cold condenses, heat liquefies it.
The elements of which it is composed, not being similar in character or
specific gravity, undergo rapid changes when at rest. The oily
particles, being lighter than the rest, soon begin to separate from
them, and rise to the surface in the form of a yellowish semi-liquid
cream, while the greater specific gravity of the serous matter, or whey,
carries it to the bottom.
A high temperature very soon develops acidity, and hastens the
separation of the cheesy matter, or curd, from the whey. And so the
three principal elements are easily distinguished.
But the oily or butyraceous matter, in rising to the surface, brings up
along with it many cheesy particles, which mechanically adhere to it,
and give it more or less of a white instead of a yellow color; and many
watery or serous particles, which make it thinner, or more liquid, than
it otherwise would be. If it rose up free from the adhesion of the other
elements, it would appear in the form of pure butter, and would not need
to undergo the process of churning to separate it from other substances.
The time may come when some means will be devised, either mechanical or
chemical, to separate the butter particles from the rest instantaneously
and completely, and thus avoid the often long and tedious process of
churning.
The coagulation, or collecting together of the cheesy particles, by
which the curd becomes separated from the whey, sometimes takes place so
rapidly, from the effect of great heat, or sudden changes in the
atmosphere, that there is not time for the butter particles to rise to
the surface, and they remain mixed up with the curd.
Nor does the serous or watery matter remain distinct or free from the
mixture of particles of the cheesy and buttery matters. It also holds in
suspension some alkaline salts and sugar of milk, to the extent of from
three to four per cent. of its weight.
We have, then,
{Butter. }
{Cream. {Butter-milk.} Water.
Milk. { {Buttery and cheesy residuum.}
{Skimmed milk. {Curd. {Sugar of milk. } Pure
{Whey. {Salts. } water.
It may be stated, in other words, that milk is composed chiefly of
caseine, or curd, which gives it its strength, and from which cheese is
made; a butyraceous or oily substance, which gives it its richness; a
sugar of milk, to which it owes its sweetness, and a watery substance,
which makes it refreshing as a beverage; together with traces of
alkaline salts, from whence are derived its flavor and medicinal
properties; and that these constituents appear in proportions which vary
in different specimens, according to the breed of the animal, the food,
the length of time after parturition, etc.
Milk becomes sour, on standing exposed to a warm atmosphere, by the
change of its sugar of milk into an acid known as lactic acid; and it is
owing to this sugar, and the chemical changes to which it gives rise,
that milk is susceptible of undergoing all degrees of fermentation, and
of being made into a fermented and palatable but intoxicating liquor,
which, by distillation, produces pure alcohol. This liquor is
extensively used in some countries. The arrack of the Arabs is
sometimes made from camel’s milk.
The Tartars make most of their spirituous liquors from milk; and for
this purpose they prefer mare’s milk, on account of its larger
percentage of sugar, which causes a greater and more active
fermentation. The liquor made from it is termed milk-wine, or khoumese.
It resembles beer, and has intoxicating qualities. The process of
manufacture is very simple. The milk, being allowed first to turn sour,
is then heated to the proper temperature, when it begins to ferment; and
in a day in summer, or two or three days in winter, the process is
completed, and the liquor may be kept several weeks without losing its
good qualities.
The admirable though complicated organization of the udder and teats of
the cow has already been explained, in speaking of the manner of
milking. But it may be said, in general, that the number of stomachs or
powerful digestive organs of the ruminants is wonderfully adapted to
promote the largest secretions of every kind.
The udder of the cow, the more immediate and important receptacle of
milk, and in which other milk-vessels terminate, is divided into two
sections, and each of these sections is subdivided into two others,
making four divisions, each constituting in itself, to some extent, an
organ of secretion. But it is well known that, as a general thing, the
lateral section, comprising the two hind teats, usually secretes larger
quantities of milk than the front section, and that its development,
both external and internal, is usually the greatest.
Milk is exceedingly sensitive to numerous influences, many of which are
not well understood. It is probably true that the milk of each of the
divisions of the udder differs to some extent from that of the others in
the same animal; and it is well known that the milk of different cows,
fed on the same food, has marked differences in quality and composition.
But food, no doubt, has a more powerful and immediate effect than
anything else, as we should naturally suppose from the fact that it goes
directly to supply all the secretions of the body. Feeding exclusively
on dry food, for instance, produces a thicker, more buttery and cheesy
milk, though less abundant in quantity, than feeding on moist and
succulent food. The former will be more nutritive than the latter.
Cows in winter will usually give a milk much richer in butter and less
cheesy than in summer, for the same reason; while in summer their milk
is richer in cheese and less buttery than in winter. As already
intimated, the frequency of milking has its effect on the quality.
Milking but once a day would give a more condensed and buttery milk than
milking twice or three times. The separation of the different
constituents of milk begins, undoubtedly, before it leaves the udder;
and hence we find that the milk first drawn from the cow at a milking is
far more watery than that drawn later, the last drawn, commonly called
the strippings, being the richest of all, and containing from six to
twelve times as much butter as the first.
Many other influences affect the milk of cows, both in quantity and
quality, as the length of time after calving, the age and health of the
cow, the season of the year, etc. Milk is whiter in color in winter than
in summer, even when the feeding is precisely the same. At certain
seasons the milk of the same cow is bluer than at others. This is often
observable in dog-days.
The specific gravity of milk is greater than that of water, that of the
latter being one thousand, and that of the former one thousand and
thirty-one on an average, though it varies greatly as it comes from
different cows, and even at different times from the same cow. A feeding
of salt given to the cow will, in a few hours, cause the specific
gravity of her milk to vary from one to three per cent.
Milk will ordinarily produce from ten to fifteen per cent. of its own
volume in cream; or, on an average, not far from twelve and a half per
cent. Eight quarts of milk will, therefore, make about one quart of
cream. But the milk of cows that are fed so as to produce the richest
milk and butter will often very far exceed this, sometimes giving over
twenty per cent. of cream, and in very rare instances twenty-five or
twenty-six per cent. The product of milk in cream is more regular than
the product of cream in butter. A very rich milk is lighter than milk of
a poor quality, for the reason that cream is lighter than skim-milk.
Of the different constituents of milk, caseine is that which most
resembles animal matter, and hence the intrinsic value of cheese as a
nutritive article of food. Hence, also, the nutritive qualities of
skimmed milk, or milk from which the cream only has been removed, while
the milk is still sweet. The oily or fatty parts of milk furnish heat to
the animal system; but this is easily supplied by other substances.
From the peculiar nature of milk, and its extreme sensitiveness to
external influences, the importance of the utmost care in its management
must be apparent; and this care must begin from the moment when it
leaves the udder, especially if it is to be made into butter. In this
case it would be better, if it were convenient, to keep the different
kinds of milk of the same milking by itself--that which comes first from
the udder, and that which is drawn last; and if the first third could be
set by itself, and the second and the third parts by themselves, the
time required to raise the cream of each part would doubtless be
considerably less than it is where the different elements of the milk
are so intimately mixed together in the process of milking, after being
once partially separated, as they are before they leave the udder.
After milking, as little time as possible should elapse before the milk
is brought to rest in the pan. The remarks of Dr. Anderson on the
treatment of milk are pertinent in this connection. “If milk,” says he,
“be put into a dish and allowed to stand until it throws up cream, the
portion of cream rising first to the surface is richer in quality and
equal in quantity to that which rises in a second equal space of time;
and the cream which rises in a second interval of time is greater in
quantity and richer in quality than that which rises in a third equal
space of time. That of the third is greater than that of the fourth, and
so of the rest; the cream that rises continuing progressively to
decrease in quantity and quality, so long as any rises to the surface.
“Thick milk always throws up a much smaller proportion of the cream
which it actually contains than milk that is thinner, but the cream is
of a richer quality; and if water be added to that thick milk, it will
afford a considerably greater quantity of cream, and consequently more
butter, than it would have done if allowed to remain pure; but its
quality at the same time is greatly deteriorated.
“Milk which is put into a bucket or other proper vessel, and carried in
it to a considerable distance, so as to be much agitated and in part
cooled before it be put into the milk-pans to settle for cream, never
throws up so much or so rich a cream as if the same milk had been put
into the milk-pans, without agitation, directly after it was milked.”
Milk as it comes from the cow is about blood-heat, or 98° Fah. It should
be cooled off as little as possible before coming to rest. With this
object in view, the pails may be rinsed with hot water before milking,
and the distance from the place of milking to the milk-room should be as
short as possible; but, even with all these precautions, the fall in
temperature will be considerable.
From what has already been said with regard to the manner in which the
cream or oily particles of the milk rise to the surface, and the
difficulty of rising through a great space, on account of their intimate
entanglement with the cheesy and other matters, the importance of using
shallow pans must be sufficiently obvious.
To facilitate and hasten the rising of the butter or oily particles, the
importance of keeping the milk-room at a uniform and pretty high
temperature will be equally obvious. The greatest density of milk is at
or near the temperature of 41° Fah.; and at this point the butter
particles will, of course, rise with the greatest difficulty and
slowness, and bring up a far greater amount of cheese particles than
under more favorable circumstances. These caseous and watery matters, as
has been already stated, cause the cream or the butter to look white,
and to ferment and become rancid. To avoid this, the temperature is
generally kept, in the best butter-dairies, as high as from 58° to 62°.
Some recommend keeping the milk at over 70°, and from that to 80°, at
which temperature the cream, they say, rises very rapidly, especially if
the depth through which it has to rise is but slight. But that, in the
opinion of most practical dairymen, is too high.
To obtain the greatest amount of cream from a given quantity of milk,
the depth in the pan should, it seems to me, never exceed two inches. A
high temperature and shallow depth, as they liquefy the milk and
facilitate the rising of the particles, tend to secure a cream free
from the cheesy matter, and such cream will make a quality of butter
both more delicate to the taste, and less likely to become rancid, than
any other.
It has already been intimated, in another connection, that neither the
largest quantity nor the best quality of milk is given by the cow till
after she has had two or three calves, or has arrived at the age of five
or six years. It may also be said, what cannot fail to have attracted
the attention of observing dairymen, that in very dry seasons the
quantity of milk yielded will generally be less, though the quality will
be richer, than in moist and mild seasons.
Hence it may be inferred that moist climates are much more favorable to
the production of milk than dry ones; and this also has been frequently
observed and admitted to be a well-known fact. From these facts it may
be stated that dry and warm weather increases the quantity of butter,
but it is also true that cooler weather produces a greater amount of
cheese. A state of pregnancy, it is obvious, must reduce the quality of
the milk, and cause it to yield less cream than before.
In the treatment of milk the utmost cleanliness is especially requisite.
The pails, the strainers, the pans, the milk-room, and, in short,
everything connected with the dairy, must be kept neat and clean to an
extent which few but the very best dairy-women can appreciate. The
smallest portion of old milk left to sour in the strainers or pans will
be sure to taint them, and impart their bad flavor to the new milk put
into them. Every one is familiar with the fact that an exceedingly small
quantity of yeast causes an active fermentation. The process is a
chemical one, and another familiar instance of it is in the distillation
of liquors and the brewing of beer, where the malt creates a very active
fermentation. In a similar manner the smallest particle of sour milk
will taint a large quantity of sweet.
The milk-room should be removed from dampness, and all gases which might
be injurious to the milk by infecting the atmosphere. If the state of
the atmosphere and the temperature, as has been stated, affect it, all
contact with foreign substances to which it is liable in careless and
slovenly milking, and all air rendered impure by vegetables and
innumerable other things kept in a house-cellar, will be much more
liable to taint and injure it. Milk appears to absorb odors from objects
near it, to such an extent that a piece of catnip lying near the pan has
been known to impart its flavor to it.
Milk, as sold in most large cities, is often adulterated to a great
extent, but most frequently with water. Not unfrequently, too, a part of
the cream is first taken off, and water afterwards added; in which case
the use of burnt sugar is very common for coloring the milk, the
blueness of which would otherwise lead to detection. The adulteration of
pure milk from the healthy cow by water, though dishonest, and
objectionable in the highest degree, is far less iniquitous in its
consequences than the nefarious traffic in “swill-milk,” or milk
produced from cows fed entirely on “still-slops,” from which they soon
become diseased, after which the milk contains a subtle poison, which is
as difficult of detection by any known process of chemistry as the
miasma of an atmosphere tainted with yellow fever or the cholera. The
simple fact is sufficiently palpable, that no pure and healthy milk can
be produced by an unhealthy and diseased animal; and that no animal can
long remain healthy that is fed on an unnatural food, and treated in the
manner too common around the distilleries of many large cities.
[Illustration: Fig. 71.]
It is evident, from the well-known influence which “still-slops” and
other exceedingly succulent food have in increasing the amount of water
in the milk, that adulteration may be effected by means of the food, as
well as by addition of water to the milk itself. It is evident, too, on
a moment’s reflection, that the specific gravity of pure milk must vary
exceedingly, as it comes from different cows, or from the same cow at
different times. This variation reached to the extent of twenty-three
degrees in the milk of forty-two different cows, or from one thousand
and eight to one thousand and thirty-one; but so great a variation is
very rare, and not to be expected.
No reliable conclusion, as to whether a particular specimen of milk has
been adulterated or not, can therefore be drawn from the differences in
specific gravity alone. A radical difficulty attending this test arises
from the fact that the specific gravity both of water and cream is less
than that of pure milk. If, therefore, the hydrometer sinks deeper into
the fluid than would be expected in ordinary pure milk, how is it
possible, unless the variation is very large, to tell whether it is due
to the richness of the milk in cream, or to the water? I have, for
instance, two instruments, each labelled “Lactometer,” but both of which
are simple hydrometers (Fig. 71), or specific gravity testers, one of
which is graduated with the water-mark 0 and that of pure milk 20°; the
water-mark of the other being 0, like the first, and that of pure milk
100°. Both are the same in principle, the only difference being in the
graduation. On the former, graduated for pure milk at 20°, it is
difficult to tell with accuracy the small variations in the percentage
of water or cream, the divisions on the scale are so minute, while the
latter marks them so that they can be read off with greater ease and
precision.
For the purpose of showing the difference in the specific gravity in
different specimens of pure milk, taken from the cows in the morning,
and allowed to cool down to about 60°, I used the latter instrument with
the following results: The first pint drawn from a native cow stood at
101°, the scale being graduated at 100° for pure milk. The last pint of
the same milking, being the strippings of the same cow, stood at 86°.
The mixture of the two pints stood at about 93¹⁄₂°. The milk of a
pure-bred Jersey stood at 95°, that of an Ayrshire at 100°, that of a
Hereford at 106°, that of a Devon at 111°, while a thin cream stood at
66°. All these specimens of milk were pure, and milked at the same time
in the morning, carefully labelled in separate vessels, and set upon the
same shelf to cool off; and yet the variations of specific gravity
amounted to 25°, or, taking the average quality of the native cows’ milk
at 93¹⁄₂°, the variations amounted to 17¹⁄₂°.
But, knowing the specific gravity, at the outset, of any specimen of
milk, the hydrometer would show the amount of water added. This cheap
and simple instrument is therefore of frequent service.
The lactometer is a very different instrument, and measures the
comparative richness of different specimens of milk. It is of very great
service both in the butter and cheese dairy, for testing the comparative
value of different cows for the purposes for which they are kept. This
instrument is very simple and cheap and the practical dairyman can tell
by it what cows he can best part with without detriment to his
business. No cow should be admitted to a herd kept for butter-making
without knowing her qualities in this respect.
Many would find, on examination, that some of their cows, though giving
a good quantity, were comparatively worthless to them. Such was the
experience of John Holbert, of Chemung, New York, who, in his statement
to the state agricultural society, says: “I find, by churning the milk
of each cow separately, that one of my best cows will make as much
butter as three of my poorest, _giving the same quantity_ of milk. I
have kept a dairy for twenty years, but I never until the past season
knew that there was so much difference in cows.”
[Illustration: Fig. 72. Lactometer.]
The simplest form of the lactometer is a series of graduated glass tubes
(Fig. 72), or vials, of equal diameter; generally a third of an inch
inside, and about eleven inches long. The tubes are filled to an equal
height, each one with the milk of a different cow, and allowed to stand
for the cream to rise. The difference in thickness of the column of
cream will be very perceptible, and it will be greater than most people
imagine. The effect of different kinds of food for the production of
butter may be studied in the same way. This form of the lactometer was
invented by Sir Joseph Banks.
Various means are used for the preservation of milk. One of these is by
concentrating it by boiling. Where this is followed, as it is by some
dairymen, as a regular business, the milk is poured, as it comes from
the dairy, into long, shallow, copper pans, and heated to a temperature
of a hundred and ten degrees, Fahrenheit. A little sugar is then mixed
in, and the whole body of milk is kept in motion by stirring for some
three or four hours. The water is evaporated, leaving the milk about one
fourth of its original bulk. It is now put into tin cans, the covers of
which are soldered on, when the cans are lowered into boiling water.
After remaining a while, they are taken out and hermetically sealed, in
which condition the milk will keep for months. Concentrated milk may
thus be taken to sea or elsewhere. Another form is that of solidified
milk, in which state it is easily and perfectly soluble in water; and
when so dissolved with a proper proportion of water, it assumes its
original form of milk, and may be made into butter. A statement by Dr.
Dorémus, in the New York _Medical Journal_, explains the process, as
follows:
“To one hundred and twelve pounds of milk twenty eight pounds of
Stuart’s white sugar were added, and a trivial portion of bicarbonate of
soda,--a teaspoonful,--merely enough to insure the neutralizing of any
acidity, which, in the summer season, is exhibited even a few minutes
after milking, although inappreciable to the organs of taste. The sweet
milk was poured into evaporating pans of enamelled iron, imbedded in
warm water heated by steam. A thermometer was immersed in each of these
water-baths, that, by frequent inspection, the temperature might not
rise above the point which years of experience have shown advisable. To
facilitate the evaporation, by means of blowers and other ingenious
apparatus a current of air is established between the covers of the pans
and the solidifying milk. Connected with the steam-engine is an
arrangement of stirrers, for agitating the milk slightly, while
evaporating, and so gently as not to _churn_ it. In about three hours
the milk and sugar assumed a pasty consistency, and delighted the
palates of all present. By constant manipulation and warming, it was
reduced to a rich, creamy-looking powder, then exposed to the air to
cool, weighed into parcels of a pound each, and by a press, with the
force of a ton or two, made to assume the compact form of a tablet (the
size of a small brick), in which shape, covered with tin-foil, it is
presented to the public.
“Some of the solidified milk which had been grated and dissolved in
water the previous evening was found covered with a rich cream; this,
skimmed off, was soon converted into excellent butter. Another solution
was speedily converted into wine-whey by a treatment precisely similar
to that employed in using ordinary milk. It fully equalled the
expectations of all; so that solidified milk will hereafter rank among
the necessary appendages to the sick room. In fine, this article makes
paps, custards, puddings, and cakes, equal to the best milk; and one may
be sure it is an unadulterated article, obtained from well-pastured
cattle, and not the produce of distillery slops; neither can it be
_watered_. For our steamships, our packets, for those travelling by land
or by sea, for hotel purposes, or use in private families, for young or
old, we recommend it cordially as a substitute for fresh milk.”
A pound of this solidified milk, it is said, will make five pints when
dissolved in water.
Another favorite form in which milk is used is that known as ice-cream,
a cheap and healthy luxury during the summer months. It is frozen in a
simple machine made for the purpose, in the best form of which the time
of the operation is from six to ten minutes. The richest quality of
ice-cream is made from cream, in the following manner: To one quart of
cream use the yolks of three eggs. Put the cream over the fire till it
boils, during which time the eggs are beaten up with half a pound of
white sugar, powdered fine; and when the cream boils stir it upon the
eggs and sugar, then let it stand till quite cold, then add the juice of
three or four lemons. It is then ready to put into the freezer. The heat
of the cream partially cooks the eggs, and the stirring must be
continued to prevent their cooking too much.
A somewhat simpler receipt, given by the confectioners, is the
following: To half a pound of powdered sugar add the juice of three
lemons. Mix the sugar and lemon together, and then add one quart of
cream. This is less rich and delicate than the preceding, but is quite
rich enough for common use, and some trouble is saved.
The following receipt makes a very good ice-cream.
Two quarts of good _rich_ milk; four fresh eggs; three quarters of a
pound of white sugar; six teaspoons of Bermuda arrow-root. Rub the
arrow-root smooth in a little cold milk, beat the eggs and sugar
together, bring the milk to the boiling point, then stir in the
arrow-root; remove it then from the fire, and immediately add the eggs
and sugar, stirring briskly, to keep the eggs from cooking, then set
aside to cool. If flavored with extracts, let it be done _just before_
putting it in the freezer. If the vanilla bean is used, it must be
boiled in the milk. The preparation must be _thoroughly cooled_ before
the freezing is proceeded with.
The ice-cream by this receipt may be produced at a cost not exceeding
twenty-five cents a quart, calling the milk five cents a quart, and the
eggs a cent apiece, and including the cost of labor. It is quite equal
to that commonly furnished by the confectioners at seventy-five cents a
quart. The arrow-root may be dispensed with. The freezer is a cheap and
simple machine.
After the cream has frozen in the machine, it should stand an hour or
two to harden before it is used.
* * * * *
To secure a more uniform flow and a richer quality of milk, cows are
sometimes spayed, or castrated. The milk of spayed cows is pretty
uniform in quantity, and this quantity will be, on an average, a little
more than before the operation was performed. But few instances have
come under my observation, and those few have resulted satisfactorily,
the quality of the milk having been greatly improved, the yield becoming
regular for some years, and varying only by the difference in the
succulence of the food. The proper time for spaying is about five or six
weeks after calving, or at the time when the largest quantity of milk is
given. There seem to be some advantages in spaying for milk and butter
dairies, where the raising of stock is not attended to. The cows are
more quiet, never being liable to returns of seasons of heat, which
always more or less affect the milk both in quantity and quality. They
give milk nearly uniform in these respects, for several years, provided
the food is uniformly succulent and nutritious. Their milk is influenced
like that of other cows, though to less extent, by the quality and
quantity of food; so that in winter, unless the animal is properly
attended to, the yield will decrease somewhat, but will rise again as
good feed returns. This uniformity for the milk-dairy is of immense
advantage. Besides, the cow, when old, and inclined to dry up, takes on
fat with greater rapidity, and produces a juicy and tender beef,
superior, at the same age, to that of the ox. The operation of spaying
is simple, and may be performed by any veterinary surgeon, without much
risk of injury.
The milk of the cow has often been analyzed. It was found by Haidlen to
consist of
Water, 873.
Butter, 30.
Caseine, 48.2
Sugar of milk, 43.9
Phosphate of lime, 2.31
Magnesia, .42
Iron, .47
Chloride of Potassium, 1.44
Sodium and Soda, .66
-------
1000.
But its composition, as already intimated, varies exceedingly with the
food of the animal, and is influenced by an infinite variety of
circumstances.
Skim-milk is much more watery than whole milk. It was found by one
analysis to contain about 97 per cent. of water and 3 per cent. of
caseine.
Swill-milk, or milk from cows fed on “still-slops,” in New York, was
found by analysis to contain less than 1.5 per cent. of butter, some
specimens having even less than one per cent.
The colostrum, or milk of the cow just after calving, contains a large
proportion of cheesy matter. Its amount of caseine was found by careful
analysis to be 15.1 per cent., of butter 2.6, mucous matter 2, and water
80.3, there being only a trace of sugar of milk.
The measures for milk in common use in this country are those used for
wine and beer. The wine quart is about one fifth less than the beer
quart, and is that most commonly used in England. It is to be regretted
that no uniform standard has been adopted throughout the country.