51. KEEPING MILK CLEAN IN THE HOME.--Immediately upon delivery, the bottle containing the milk should be placed in the coolest place available, never being allowed to stand on the porch in the sun or where such animals as cats or dogs may come in contact with it. When the milk is to be used, the paper cap should be carefully wiped before it is removed from the bottle, so that any dirt that may be on top will not fall into the milk. If not all the milk is used and the bottle must be returned to the cool place where it is kept, it should be covered by means of an inverted drinking glass or, as shown in Fig. 6, by a glass or porcelain cover. Such covers, or sanitary milk caps, as they are called, are very convenient for this purpose and may be purchased at a slight cost.

52. Another precaution that should be taken is never to mix stale milk with fresh milk, because the entire quantity will become sour in the same length of time as the stale milk would. Also, milk that has been poured into a pitcher or any other open vessel and allowed to stand exposed to the air for some time should never be put back into the bottle with the remaining milk. Such milk is sure to be contaminated with the germs that are always present in the dust constantly circulating in the air. It is sometimes necessary to keep milk in a vessel other than the bottle in which it is delivered. In such an event, the vessel that is used should be washed thoroughly, boiled in clean water, and cooled before the milk is poured into it.

53. Particular care should be taken of the empty milk bottles. They should never be used for anything except milk. Before they are returned to the dairyman to be used again, they should first be rinsed with cold water, then washed thoroughly with hot, soapy water, and finally rinsed with hot water. If there is illness in the home, the washed bottles should be put into a pan of cool water, allowed to come to a boil, and permitted to boil for a few minutes. Such attention will free the bottles from any contamination they might have received. The dairyman, of course, gives the bottles further attention before he uses them again, but the housewife should do her part by making sure that they are thoroughly cleansed before they are collected by him.

54. KEEPING MILK COOL IN THE HOME.--As has been pointed out, milk should, upon being received, be kept in the coolest place available, which, in the majority of homes at the present time, is the refrigerator. In making use of the refrigerator for this purpose, the housewife should put into practice what she learned in Essentials of Cookery, Part 2, concerning the proper placing of food in the refrigerator, remembering that milk should be placed where it will remain the coolest and where it is least likely to absorb odors. She should also bear in mind that the temperature inside of a refrigerator varies with that of the surrounding air. It is because of this fact that milk often sours when the temperature is high, as in summer, for instance, even though it is kept in the refrigerator.

55. In case a refrigerator is not available, it will be necessary to resort to other means of keeping milk cool. A cool cellar or basement is an excellent substitute, but if milk is kept in either of these places, it must be tightly covered. Then, too, the spring house with its stream of running water is fully as good as a refrigerator And is used extensively in farming districts. But even though a housewife has none of these at her disposal, she need not be deprived of fresh milk, for there are still other ways of keeping milk cool and consequently fresh. A very simple way in which to keep milk cool is to weight down the bottles in a vessel that is deeper than they are and then pour cold water into the vessel until it reaches the top of the bottles, replacing the water occasionally as it becomes warm. A still better way, however, so far as convenience and results are concerned, is that illustrated in Fig. 7. As shown, wrap the bottle in a clean towel or piece of cotton cloth so that one corner of it is left loose at the top. Then place this end in a pan of cold water that stands higher than the bottle. Such an arrangement will keep the cloth wet constantly and by the evaporation of the water from it will cause the milk to remain cool.

COOKING MILK

56. POINTS TO BE OBSERVED IN COOKING MILK.--Because of the nature of milk and its constituents, the cooking of this liquid is a little more difficult than would appear at first thought. In fact, heating milk to a temperature greater than 155 degrees Fahrenheit causes several changes to occur in it, one of which, the coagulation of the albumin, has already been mentioned. As the albumin hardens into the layer that forms on the top of boiled milk, a certain amount of fat, sugar, and casein becomes entangled in it, and if the coagulated skin is rejected, these food substances, in addition to the albumin, are lost. Another change that results from boiling is in the fat globules that remain, for these separate and exist no longer in the form of cream.

57. When milk that is not perfectly fresh is cooked with other materials or soups, sauces, and puddings it sometimes curdles. To prevent curdling, the milk should be heated as rapidly as possible before it is used with the other ingredients. While the separate heating of the milk involves a little more work, time may be gained by heating the milk while the remaining ingredients are being prepared. The curdling of comparatively fresh milk is often caused by the addition of salt, especially if the salt is added when the milk is hot. However, if a pinch of bicarbonate of soda is added to the milk before it is heated, it will not be likely to curdle even though it is not absolutely fresh. When tomato is to be used in soup that contains milk or cream, curdling can be prevented if the milk or the cream to be used is thickened with flour or corn starch or a little soda is added to the tomato before the two are mixed. The mixing is accomplished by pouring the tomato into the milk instead of the milk into the tomato. When acid fruit juices are to be added to milk or cream and the mixture then frozen, curdling can be prevented by thoroughly chilling the milk or cream in the freezer can before combining it with the juices.