Woman's Institute Library of Cookery. Volume 2: Milk, Butter and Cheese; Eggs; Vegetables

by Woman's Institute of Domestic Arts and Sciences

CHARACTERISTICS OF WHOLESOME MILK

21. So far as the housewife is concerned, the qualities that characterize wholesome milk are without doubt of great interest. She may know of what use milk is in the diet and the food substances of which it is composed, but unless she understands just what constitutes milk of good quality, as well as the nature of inferior milk, she cannot very well provide her family with the kind it should have. Therefore, to assist her in this matter, the characteristics of wholesome milk are here discussed. Such milk, it will be well to note, must be of the right composition, must not be adulterated, must be fresh--that is, not older when delivered than is permitted by law--and must be as clean as possible.

22. STANDARD OF MILK COMPOSITION.--The housewife usually judges the quality of milk by the amount of cream that rises to the top when milk in a bottle is allowed to remain undisturbed for some time. This is really an excellent test, because milk that contains only a small amount of cream is of poorer quality than that which contains a larger amount; in other words, the more cream milk contains, the higher will be its food value and the greater its energy-producing ability. Then, too, milk that is rich in cream usually contains proportionately large amounts of protein and sugar.

While the composition of milk has much to do with the quality of this food, it varies, as should be noted, in different breeds and even in individual cows, depending on both the food and the care given to them. For this reason, milk that is mixed is preferable to the milk of a single cow, as the mixing of the milk of a number of cows insures a better average composition.

23. ADULTERATION OF MILK.--The composition of milk, and hence its quality, is seriously affected by its adulteration. By this is meant the extraction of any of the food substances from whole milk; the addition of anything that tends to weaken or lower its quality or strength; the use of coloring matter to make it appear of greater value than it actually is; or the use of preservatives to prevent it from souring as soon as it ordinarily would. It is, of course, illegal to adulterate milk, yet it is sometimes done. The most convenient and possibly the most common materials used to adulterate milk are water and skim milk. The addition of water to milk decreases the quantity of all its food substances, but the addition of skim milk reduces the quantity of fat only. The color of the milk is often affected by the use of these adulterants, but when this happens, yellow coloring is usually added to restore the original appearance.

Sometimes the milk that a dairyman markets contains more fat than the law requires; but even such milk cannot legally be skimmed nor diluted with skim milk. The only thing that may be done to it is to mix it with milk that is low in butter fat and thus obtain a milk that will average the legal percentage. For instance, if milk from a dairy averages 5 per cent, of butter fat, it may be diluted with milk that contains only 3 per cent, of butter fat, because the result of such mixing, which will be milk averaging 4 per cent, of this food substance, will be the legal standard.

24. To prevent milk from souring, dishonest milk dealers often put into it such preservatives as soda, borax, and formaldehyde. There is no definite way of telling whether or not one of these has been used, except by a chemical analysis. However, if milk does not sour within a reasonable time when no precautions have been taken to keep it sweet, it should be looked on with suspicion, for it undoubtedly contains a preservative.

25. FRESHNESS OF MILK.--To be most satisfactory for all purposes, milk should be absolutely fresh. However, it is almost impossible to obtain milk in this condition, because it is generally sold at a distance from the source of supply. Milk that is sold in small towns and cities is usually 12 and often 18 to 21 hours old when it is delivered; whereas, in large cities, where the demand is so great that milk must be shipped from great distances, it is often 24 to 36 or even 48 hours old when it reaches the consumer. In order that milk may remain sweet long enough to permit it to be delivered at places so far removed from the source of supply, it must be handled and cared for in the cleanest possible way by the dealers. Likewise, if the housewife desires to get the best results from it, she must follow the same plan, cooling it immediately on delivery and keeping it cool until it is consumed. The freshness of milk can be determined only by the length of time it will remain sweet when proper care is given to it.

26. CLEANLINESS OF MILK.--Milk may be of the right composition, free from all adulteration, and as fresh as it is possible to obtain it, but unless it is clean, it is an injurious food. Milk is rendered unclean or impure by dirt. In reality, there are two kinds of dirt that may be present in milk, and it is important to know just what these are and what effect they have on milk.

27. The less harmful of the two kinds of dirt is the visible dirt that gets into the milk from the cow, the stable, the milker, the milking utensils, and similar sources when these are not scrupulously clean. If milk containing such dirt is allowed to stand long enough in pans or bottles for the heavier particles to settle, it will be found as sediment in the bottom of the receptacle. To say the least, the presence of such dirt is always disagreeable and frequently produces foreign flavors.

Straining the milk through clean absorbent cotton will reveal the presence of such dirt and another kind of dirt that does not show through the opaque fluid. This second kind of dirt is generally found in milk when the first kind is present in any quantity. It is more liable to be harmful than the other, because it enters the milk from the water used in cleaning the receptacles or from some contaminated source.

28. Whenever dirt is present in milk, bacteria are sure to be there; and the greater the quantity of dirt the greater will be the number of bacteria. Should the housewife desire to compare the cleanliness of several lots of milk, she may filter a like quantity from each lot, say a quart or a pint, through small disks of absorbent cotton. If, after the milk has passed through the cotton disk, very little dirt remains on it, as in Fig. 2 (a), the milk may be considered as comparatively clean; if the cotton disk appears as in (b), the milk may be said to be only slightly dirty; if it appears as in (c), the milk is dirty; and if it appears as in (d), the milk is very dirty. Milk that leaves a stain like that in (d) contains more bacteria than milk that leaves a stain like that in (c), and so on through all the lots of milk. Filtering milk in this manner, however, does not indicate whether the bacteria are disease producing. Such information can be secured only by microscopic examination, and only then by persons who have a knowledge of such matters.

29. Since, as has been pointed out, bacteria cling to all dirt, the dirt that milk contains is one of the causes of souring and putrefaction of milk, and may be a cause of disease. Indeed, it is definitely known that dirty milk sours much more quickly than does clean milk. Actual tests in which clean milk was put in a cool place have proved that it will keep for weeks, whereas dirty milk will sour in a day or two, especially in warm weather. This information should point out clearly to the housewife that it is not merely heat that changes milk or causes it to sour. She should understand in addition, that bacteria grow and multiply very rapidly when conditions for their growth are provided. These conditions are moisture, warmth, and the right kind of food, and as all of these are found in milk, this product is really ideal for bacterial development. The only way in which to protect milk is to make sure that no bacteria enter it, or, if they do, to make it impossible for them to grow. This may be done by keeping the milk so cold that they cannot thrive, or by destroying them in various ways, which are taken up later.

30. In former times, there was not much danger of wide-spread disease from the milk supply, for it was cared for almost entirely by those who kept a few cows and distributed milk to a small number of customers. In fact, it has been only within the past 50 years that large quantities of milk are handled by separate dairies and shipped great distances from the source of supply and that the distribution of milk has become a great industry. When so much milk is handled in one place, it is more or less unsafe unless the dairy is kept extremely clean and is conducted in the most sanitary manner. Experience has shown that too much attention cannot be given to the care of milk, for the lives of great numbers of children have been sacrificed through the carelessness of dairymen and persons selling and distributing milk, as well as through the negligence of those who handle the milk after it has entered the home. To overcome much of this carelessness, both the Federal Government and the various states of this country have set standards for safe milk production, and in order to make their laws effective have established inspection service. Independently of these state and national laws, many of the cities, particularly the large ones, have made their own standards, which, as a rule, are very rigid. One of the usual requirements is to compel each person who wishes to sell milk in the city to buy a license, so that the city authorities may keep in touch with those handling milk and so that conditions may be investigated at any time. In view of the care required of dealers in handling milk, the housewife owes it to herself and the members of her family to keep the milk in the home in the best possible manner.