Besides milk that is commonly sold by dairymen and milk dealers, it is possible to buy in the market many grades of so-called PRESERVED MILK. Such milk is produced by driving off all or part of the water contained in milk, and it is sold as condensed, evaporated,and powdered milk. Usually, it is put up in tin cans, and while it is not used so extensively as regular milk, many firms are engaged in its preparation.
As has just been mentioned, condensed and evaporated milk is produced by the complete or partial evaporation of the water contained in milk. Such milk can be shipped long distances or kept for long periods of time, because it does not contain sufficient moisture to permit the growth of bacteria. In evaporating milk to produce these preserved milks, each gallon is diminished in quantity to about two and one quarter pints, the original 87 per cent. of water being reduced to about 25 per cent. Therefore, in order to use such milk, sufficient water must be added to restore it to its original composition. Sometimes comparatively large amounts of cane sugar are added to such milks, which, besides sweetening them, assist in their preservation. If cane sugar is not used, the milks are usually made sterile in order to prevent them from spoiling.
The form of preserved milk known as powdered milk is the result of completely evaporating the water in milk. Such milk has the appearance of a dry powdered substance. It does not spoil easily and is so greatly reduced in quantity that it can be conveniently stored. Because of these characteristics, this product, for which skim milk is generally used, is extensively manufactured. It is used chiefly by bakers and confectioners, and, as in the case of evaporated or condensed milk, the water that has been evaporated in the powdering process must be supplied when the milk is used. In order that a definite idea may be formed of the sanitary and bacteriological standards that are set by milk commissions, there are here given, in Table I, the regulations governing the grades and designation of milk and cream that may be sold in the city of New York. As will be observed from a study of this table, only definite grades of milk and cream can be sold in that city; likewise, it must conform to certain standards of purity and the producer must handle it in such a way that it may be delivered to the consumer in as clean and fresh a condition as possible. Without doubt, a grading similar to this one will become general throughout the United States eventually, for this is the only way by which the housewife may know with certainty whether or not the milk she purchases is of the right composition and is safe, fresh, and sanitary in every respect. The different qualities of milk and cream as shown by this grading are, of course, sold at different prices, those which require the greatest care and expense in handling selling for the highest price. After the housewife has become familiar with the points that she should know concerning milk, she will be much better equipped to purchase milk of the right kind for her home. However, there are still some points for her to observe when she is purchasing milk if she would supply her family with the best quality of this food.
In the first place, she should buy milk from a reliable dealer who will not object to questioning, and, if possible, she should make an investigation of the dairy that supplies the milk that she uses. If she cannot investigate the dairy personally, she should at least endeavor to obtain information from those who are prepared to give it. If she learns that the conditions in the dairy that is supplying her with milk are not what they should be, she should try to obtain milk from some other source. Of course, she should remember that milk of the best and cleanest quality is the highest in price, because of the increased cost of production; but it is usually advisable to pay the higher price, especially if children are to be fed, because cheap milk is liable to be unsafe, at least for any purpose that will require it to be served without cooking. Should the income not allow the best quality of milk to be used for all purposes, a cheaper grade can be used for cooking, but it is always economical to purchase the best quality when this food is to be used as a beverage.