CHAPTER I

PRODUCTION, COMPOSITION AND CHARACTERISTICS OF MILK, MILK FERMENTS, PASTEURIZATION

DAIRY CATTLE

A number of typical but widely different breeds of dairy cows have been developed in various dairy countries, each owing to the soil and the climatic conditions of its home, as well as to the skill and fancy of the breeders, its characteristic features, form, color, etc.

=Milk-Breeds.=—The black and white _Holstein-Friesians_ (which, by the way, had their home in Holland and not in Holstein) are known for their large production of not very rich milk, while the _Guernseys_ and _Jerseys_ give milk exceedingly rich in butter-fat. A good Holstein cow will give from 7,000 to 10,000 lbs. of milk in a year, containing from 3¼% to 4% butter-fat. Some of them produce as much as 20,000 to 30,000 lbs. in a year—nearly 4,000 gallons—just think of it! Jersey cows will usually not produce as much in quantity as the Holsteins but Jersey milk often contains 5% or 6% or more butter-fat, and a few of the best have been known to produce 800 to 900 lbs. of butter in one year, an amount equal to the cow’s own weight. The red _Danish_ cow is an exceedingly good and highly bred milk producer which, however, has not been introduced in the United States, but the Scotch _Ayrshires_ and the _Brown Swiss_ are other well-known dairy breeds which are in favor with many American farmers.

But, alas! too many herds of dairy cattle average less than 5,000 lbs. of milk per cow per year and do not pay for their feed.

Many native cows respond, however, to good care and feed and with a thoroughbred bull a satisfactory herd can readily be built up from carefully selected native stock. Such continued cross-breeding is more apt to succeed than attempts to cross two thoroughbred breeds because the characteristic features in full-blooded animals are so strong as to invariably predominate in the progeny over the less pronounced forms and tendencies inherent in native cows. But where two full-blooded animals are mated and the strong characteristics in each are fighting for predominance the result is apt to be a poor, ill-proportioned offspring as the result of atavism.

=Beef-Cattle.=—Cattle bred and developed for the purpose of producing beef rather than milk are called by contrast beef-cattle. As examples of beef-cows look at the _Shorthorns_ or the _Herefords_ or the _Polled Angus_ at the next State Fair you visit and notice the square, deep, smooth body with muscles and fat strongly developed in contrast to the loosely built, bony milk-cow with its tendency to turn all its food into milk at the expense of the body. There are, however, also among the Shorthorns, strains of good milkers, but as a rule these beef-breeds are not selected for the dairy farm, and “dual purpose” cows are not usually profitable.

=Food and Water.=—The natural food for the dairy cow in summer is grass, and where rich, succulent grass and clover grow in abundance, as on the fertile meadows of Holland and the Channel Islands, or the Swiss Alps, the highly cultivated Danish farms, the eastern and middle-western states of America, etc., dairying early reached its highest development. As the value of milk and its products for human food became more generally recognized and all-the-year-round production was forced, it was found necessary to feed the cows heavily in winter too, not only hay, but also grain and succulent food such as beets and corn-ensilage (green corn cut, stalks, cobs and all, and packed in a silo), and science was taken into play to formulate _Balanced Rations_ containing the proper amounts and proportions of the various nutrients—Protein, Fat and Carbohydrates. It is not the place here to go deeper into this problem which has long been a subject for thorough research and experiments. In fact, more attention has been paid to the feeding of cattle than to the proper nourishment of human beings, and much of what we know about the latter has been deducted from experience and study on the dairy farm, and from laboratory work along that line. In the chapter on “Milk as a Food” we are taking up food values, etc., in relation to the feeding of children and men. Suffice it here to say that the same fundamental principles apply to the feeding of calves and cattle for the production of milk and beef. And we wish to emphasize the fact that, with due consideration to the proper proportion between the various groups of nutrients, it is much more important that the food is succulent, appetizing and easily digestible than that the ration shall be accurately balanced.

This fact, long well known to practical breeders and dairymen, has recently been confirmed by Dr. E. V. McCullom to whose experiments further reference is made in the chapter on milk as a food for children. He shows that there is a very great difference in the quality of Protein and Fat from various sources and that there is “Something Unknown” in butter-fat, for instance, which is absent in most other fats and which is vital for the growth of the child as well as for the proper nourishment of man. This unknown but essential substance is also found, in small quantities, in the leaves of certain plants, as in alfalfa, while it is absent in the grain of the cereals.

In modern dairy farming _alfalfa_ is considered an indispensable source for protein, and corn-ensilage or beets for carbohydrates, while bran, cottonseed meal or oil cake, malt-sprouts, gluten, distillers’ grain, etc., may be used to advantage in various combinations.

Contrary to a general impression one cannot feed fat into the milk. A large amount of oil cake or other food rich in fat in the daily ration does not increase the percentage of butter-fat in the milk. Rather, it depends largely upon the breed and to some extent upon the period of lactation. Provided the food agrees with her digestion and keeps the cow in a good, healthy condition, the composition of the milk is not changed to any appreciable extent by a change in make-up of the food.

It goes without saying that to produce from 20 to 50 lbs. of milk a day the cow must have an abundance of _fresh, pure water_ to drink and she should not have access to stagnant water.

=The Barn= must be clean, light and well ventilated and the cows should be milked with clean hands into a clean pail which is covered as far as possible so as to prevent dust from falling into the milk, or with one of the excellent milking machines which are now frequently used in large dairies. The milk is strained and cooled immediately after milking.

=Milking.=—The cows are usually milked twice a day; occasionally, when the highest possible yield is desired, as in important tests, three or four times. The first five days after the birth of the calf the milk,—the Colostrum so called,—is not normal and should not be used for human consumption. It may be fed to the calf. The first three to four months the yield of milk generally is higher than later, when it gradually drops until after about ten months it stops altogether and the cow goes “dry” at least for some six weeks before dropping the next calf. The highest annual yield may be obtained by having the cows “come in” in the Fall or early Winter and feeding them well all Winter to keep up an abundant flow of milk. Then, when they come out on pasture in the Spring,—in the latitude of the Great Lakes about May 15th,—the fresh, rich feed will stimulate production and give it a fresh start so that the milk-pail may continue to be filled during the next few months and the shrinkage of the yield will not occur until the time when the pastures dry up. The cow will then go dry in the early Fall, when feed is scarce. Usually, however, the cows are allowed to “come in” in the Spring and the yield of milk begins to shrink in the late Summer with little or nothing in the Winter.

=Test the Cows.=—To ascertain if a cow pays for her feed the amount and the quality of the milk should be tested and computed for the year. If the milk from each cow cannot be weighed every day it may be done regularly once a month or preferably oftener. If it is weighed morning and evening once every ten days it is easy to keep the account by multiplying the number of pounds by ten and adding the totals for the year. Occasionally the milk may be subjected to the Babcock Test to ascertain its richness; three or four times during the period of lactation is sufficient.

Where farmers do not have time to do the testing themselves they often combine and hire a young man or woman, trained in an agricultural college, to go around from farm to farm and do the work. These experts not only test the yield and the percentage of fat but also weigh and compute the feed so as to help the farmer make up his rations and calculate whether each cow pays for her feed or not. The members of these associations meet and compare notes and a friendly rivalry is stimulated which may do much toward increasing production. As a matter of fact, where Cow Test Associations have been introduced, both yield and quality of the milk have been largely increased.

=Healthy Cows= alone can be depended upon to produce sanitary milk. In many herds of milk-cows tuberculosis is prevalent, and constant vigilance is necessary to prevent its spread. The _Tuberculin Test_ discovered by Koch is invaluable for the purpose of ascertaining the presence of tuberculosis. It is not necessary, however, to kill every infected animal. Only where the lungs or the udder is affected and a physical examination shows an advanced stage of the disease such radical means are advisable. When the tuberculin test was first introduced many valuable herds were wantonly and foolishly killed off because some of the highly developed dairy cows showed reaction to the test while worthless scrubs were allowed to live and spread the disease. For only the intelligent and public-spirited owners of fine herds submitted their cows to the test, a reaction to which, under ill-advised regulations, permitted state officials to condemn the infected herds. In Denmark Dr. Bernhard Bang introduced a system of isolation of the infected animals which together with _Compulsory Pasteurization_ of the milk from such cows has proved efficient for the eradication of tuberculosis, and the _Bang Method_ is now generally recognized as the proper way of handling the matter.

COMPOSITION OF COW’S MILK

Cow’s milk contains on an average in 100 lbs.:

87 lbs. of water 4 lbs. of butter-fat 3¼ lbs. of casein and albumin (protein) 5 lbs. of milk sugar ¾ lbs. of ash (mineral matter) 100 lbs. total.

It consists therefore of 87% water and 13% “solids,” 4 of which are fat and 9, “solids—not fat.” =Butter-Fat= is found in milk in the form of minute globules suspended in the liquid. As fat or oil is lighter than water (has less specific gravity) it naturally floats and the fat globules therefore soon rise to the top when milk stands at rest, forming a layer of _cream_ which may be skimmed off from the _milk_. In chemical composition butter-fat is very nearly the same as other animal and vegetable fats, but the slight variation may make a lot of difference in digestibility and palatability as well as in nutritive value, and it is a mistake to consider Oleomargarine, Butterine, Nut-Butter and other substitutes for butter “just as good” because a chemical analysis shows them to contain “almost” the same elements or compounds. These products may be good and legitimate if sold for what they are, but should never be allowed to be sold or served for what they are not, genuine butter.

=Casein and Albumin= are the proteids or nitrogenous matters of the milk, in chemical composition and in food value much the same as the protein in beans and peas or in meat, or the white of eggs. Casein is present in much larger quantity than albumin and is distinguished from the latter by being precipitated by rennet, which has no effect on albumin. Casein may also be precipitated by acids, while it required boiling as well as acidity to throw the albumin out of solution.

=Milk-Sugar= is related to the vegetable sugars, glucose, cane sugar, etc., and remains in solution in the whey which separates out from the cheese-curd when milk is curdled with rennet or acids. The whey also contains the mineral matters or _ash_, which consists largely of phosphate of lime, of use to the young in building up bones. When whey is boiled down to a thick syrup and left to stand, the sugar will crystallize out and may be separated from the liquid, still holding in solution the mineral matters.

=Mineral Matters.=—These may be gathered as _ash_ by boiling off the water from this liquid or from the whole milk and burning the rest, as all the constituents except the ash belong to what in chemistry is called organic matter, which disappears in the air by burning.

HOW TO TEST MILK

Milk may be adulterated or decreased in value either by skimming or by watering. In either case the percentage of the most valuable constituent, the butter-fat, is diminished. It is upon this fact that the most practical test, the Babcock, is based.

=The Babcock Test.=[2]—By treating a sample of milk with strong sulphuric acid the butter-fat is liberated as an oil. By subjecting the mixture to centrifugal force the light butter oil is separated from the rest of the milk and the percentage can be easily determined. Centrifugal force had already been used in the Fjord Cream Test, but it remained for Dr. Babcock to work out the splendid practical and reliable test which bears his name and in which he has given to the world an invention of incalculable value.

=Sampling.=—Whether it is new milk or skim milk or buttermilk or cream that is to be tested the first thing to observe is to take a _truly representative sample_. The liquid must be thoroughly mixed by pouring it several times from one vessel to another, or stirring vigorously.

It may not always be convenient to make a test immediately when the sample is taken. In the creamery where the milk is paid for according to its fat contents, samples are taken every day from every patron’s milk and it would take too much time for the butter maker to test all of these samples before they would spoil. A preservative, corrosive sublimate,—poisonous but all right for the purpose,—is therefore added and all the samples of one farmer’s milk for several days or a whole week are put together in one glass to be kept and tested at one time. This is called a composite test and has proven entirely satisfactory.

=The Lactometer= has been used to discover adulterations, depending upon the difference in specific gravity of the various constituents. The specific gravity of whole milk is about 1.032 which means that, if a certain volume of water weighs 1.000 weight units, the same volume of whole milk weighs 1.032, the same volume of butter-fat weighs, say, .900, or of cream about 1.000, and of skim milk 1.036 units. If the Lactometer shows a sample of milk to have a higher specific gravity than 1.032 it may therefore be suspected of having been skimmed. But it will readily be seen that by removing from whole milk some of the cream and adding water, the specific gravity can easily be brought back to normal for whole milk. This test is therefore unreliable and has been discarded with the advent of the Babcock.

=Acidity Test.=[3]—The acidity, or sourness, of milk or cream, which depends upon the amount of lactic acid developed in it, may be tested by a liquid normal alkali or by the Farrington Alkaline Tablets, a solution of which added to sour milk neutralizes the acid. A few drops of an indicator, Phenolpthalein, added to the milk, turns it pink when all the acid has been neutralized, and the amount of alkali solution used shows the percentage of acid in the milk. This is quite important in preparing “starters” for ripening the cream in butter making or milk in cheese making, and in the manufacture of “Commercial Buttermilk,” etc.

There are other tests used in scientific dairying as the _Fermentation Test_ to ascertain the relative purity of milk, the _Casein Test_, etc., but the above are those mostly used besides the _Bacterial Count_ which is mentioned under the chapter on “Milk Supply,” and the _Rennet Test_ described under “Cheese Making.”

FERMENTS

Two classes of ferments are of importance in connection with milk: (1) “unorganized” or chemical ferments, the “enzymes,” and (2) “organized” ferments such as bacteria and yeast.

_Enzymes_

=Rennet.=—Among the unorganized ferments, _Rennet_ or _Rennin_ is highly important on account of its power of coagulating or curdling milk by precipitation of the casein. Rennet is extracted from the stomach of the suckling or milk-fed calf, where it serves in digesting the calf’s food. It is in the market in the form of a liquid extract as well as a dry powder compressed into tablets (Rennet Tablets and Junket Tablets). The characteristics and use of rennet are described under “Cheese Making” in