“Milk contaminated by the introduction of dust, dirt, fecal matter, or kept in imperfectly cleaned cans becomes fouled with gas-producing bacteria that break down the milk sugar and so produce gases and usually undesirable odors.... Therefore milks showing the presence of gas or bad odors in any considerable degree are milks that have been more or less polluted with extraneous organisms or carelessly handled, and as a consequence such milks show a type of curd revealed in [Figs. 17], [18], and [19].
Whey.
—The residue left from milk in the process of the making of cheese is known as whey. Whey consists of that portion of milk which is not precipitated by the rennet and which separates when the casein of milk is coagulated and sets in the process of cheese making. The whey contains the principal portion of the water in milk, the most of the milk sugar therein, and small quantities of butter and soluble nitrogenous portions (albumin) and solid particles which remain suspended in the solution. It may, therefore, be properly considered as milk from which the greater part of the nitrogenous portions and fat particles has been separated. The value of whey as a food product consists chiefly in the milk sugar which it contains. It is not very largely used for human food but is valued as a food for young domesticated animals, especially pigs and poultry.
Composition of Whey.
—The whey resulting from the manufacture of cheese contains nearly all the foods of the whole milk with the exception of the casein and fat. It is composed of from 6 to 8 percent of solids consisting chiefly of milk sugar, some albumin, a little fat, and about 0.6 percent of mineral matter.
Koumiss.
—Koumiss originated in Asia Minor in the production of a fermented drink from mare’s milk, which is richer in milk sugar than the lactic secretions of most other mammals. By the fermentation of the milk sugar mare’s milk is converted into a fermented beverage containing a small percentage of alcohol. In this country koumiss is made almost exclusively from cow’s milk and by special fermentation at a low temperature. It is a beverage valued especially by convalescents and invalids and frequently is capable of nourishing the body in diseases which affect the digestive organs when other foods fail of assimilation. It is also a cooling and delicious beverage for those in health when properly prepared and stored.
Modified Koumiss or Kephir.
—Koumiss made from cow’s milk with the previous addition of milk or cane sugar to increase the alcoholic content cannot be regarded as a natural product but rather one to which the term “modified” may be applied. The greater part of koumiss made in the United States from cow’s milk is of this modified variety. Cow’s milk contains on an average about 4 or 5 percent of sugar and does not yield a fermented beverage of a sufficient alcoholic content without reducing the actual sugar content of the beverage below the point of palatability. Cane sugar is usually employed as the modifying agent. While modified koumiss cannot be regarded as of equal value with the natural article made from mare’s milk it is a palatable and wholesome beverage when produced and stored under proper conditions. The quantity of alcohol produced in any case is not very great and the change in composition which renders koumiss so easily assimilable in many cases cannot be due alone to the alcohol formed but to the fermentative changes produced by enzymic action which takes place in the other constituents of koumiss, especially casein during the process of fermentation.
Koumiss or kephir, which is the name applied to koumiss made from cow’s milk, is also prepared with the addition of honey, in the place of sugar, and small quantities of wheat flour, not exceeding 20 parts to 1500 parts of other constituents. Koumiss is sometimes artificially fortified by the addition of small quantities of alcohol, but this practice must be regarded as extremely reprehensible. The alcohol of koumiss is incident to its fermentation and should not be increased beyond the normal amount. One of the important points in the making of koumiss is the control of the temperature which, during fermentation, ought not to rise above 50 degrees in order to get the best results. Koumiss may be made in the bottle in which it is kept, in fact, it is best made so, and its fermentation then resembles that of champagne. During the process of fermentation the bottle should be shaken at least once a day in order that the part which coagulates cannot be unevenly distributed throughout the mass. The bottle should be strong enough to resist the pressure produced by the carbon dioxid which is formed and the cork should be securely tied in. As in the case of champagne it is best to place the bottle with the cork down. Before using, the bottle containing the koumiss should be well shaken in order to thoroughly mix the contents which form a creamy, foamy mass extremely palatable, highly nutritious, and valuable not only as a beverage but in many cases of disease and disordered digestion as a food. In fact the value of koumiss for medicinal purposes, that is for medicinal food, is not thoroughly appreciated by the medical profession. This may be due to the fact that the art of making koumiss is not generally known, and while the general principles upon which its manufacture is based have been set forth it requires an expert to make a palatable and useful article (“British Dairy Farming” by Jas. Long). It is worthy of suggestion now that the use of horses for draft purposes has practically been superseded by the automobile and the trolley that the production of real koumiss from mare’s milk might become a very useful field of industry in the United States. It is perfectly certain that the genuine article must possess properties which are not wholly found in the imitations of koumiss which are so common in this country. It is well understood by physicians that a natural product produced from natural material is always superior in character both as a food and medicine to the synthetic or artificial product. Whenever, therefore, a fermented beverage produced from natural sources is contaminated by artificial products the resulting compound is not so useful nor digestible. For instance, wine which is made partially from sugar and beer made partially from dextrose, although they may be healthful and wholesome beverages, are inferior in quality and character to the real product made from grape juice or barley malt.