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.

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.

As has already been learned, great care must be taken in the heating of milk, because the solids that it contains adhere quickly to the bottom of the pan and cause the milk to scorch. For this reason, milk should never be heated directly over the flame unless the intention is to boil it, and even if it must be boiled every precaution should be taken to prevent it from burning. It should be remembered, too, that a very small scorched area will be sufficient to make a quantity of milk taste burned. The utensil in which milk can be heated in the most satisfactory way is the double boiler, for the milk does not come in direct contact with the heat in this utensil. If a double boiler is not available, good results can be obtained by setting one pan into another that contains water.

Milk is often used in place of water for cooking cereals, beverages, puddings, soups, etc. This is good practice and should be followed whenever possible, for when milk is added it serves to increase the nutritive value of the food. It should be observed, however, that more time is required to cook grains or cereals in milk than to cook them in water, because milk contains more solid matter than water and is not absorbed so quickly. Another frequent use of milk is in breads and biscuits, where, as is explained in Bread and Hot Breads, it produces a browner and more tender crust than water.

Because of the numerous purposes for which milk is required in the preparation of foods, the smallest amount of it, whether sweet or sour, can be utilized in cooking; therefore, no milk need ever be wasted. A few of the uses to which this food is oftenest put are mentioned briefly in order that the housewife may be familiar enough with them to call them to mind whenever she desires to carry out a recipe that calls for milk or when she has occasion to utilize milk that she has on hand. Milk thickened slightly with flour and flavored with such material as corn, asparagus, celery, tomatoes, beans, peas, orfish makes a delicious soup. In bisques, or thickened soups, and in chowders, the liquid used need not be milk, but these are made very appetizing if milk is used for part or all of the liquid. Then, too, sauces or gravies made with milk, thickened with flour, and made rich with butter or other fat lend themselves to a variety of uses. Dice of vegetables, meat, fish, or game added to a sauce of this kind and served in pastry cases or over toast provide dishes that are delightful additions to any meal.

Milk is also used as the basis for custards, blanc manges, ices, sherbets, ice creams, and tapioca, rice, and bread puddings in which eggs, starchy materials, and flavorings are added and the mixture then baked, steamed, boiled, or frozen, as the desired result may require. As is well known, milk is practically indispensable in the making of cakes, cookies, quick breads, and in fact nearly all dough mixtures. Even if it has soured, it can be used with soda to take the place of cream of tartar in mixtures that are to be made light, the lactic acid in the sour milk acting with the soda as leavening. Left-over milk in comparatively large quantities may also be used in the home for the making of cheese, although this product of milk is usually produced commercially.