A. Class Experiments. Acids and Milk.
The possible effect of heat and acids on sweet milk in making cream of tomato soup.
1. Heat a little milk which is sour, but not separated. Note the result.
2. Mix a tablespoon of tomato juice with one of milk, and heat. Note the result.
3. Add tomato juice, drop by drop, to a little milk, stirring, and see how much juice can be added before the milk separates. Then reverse the experiment, adding the milk to the tomato juice.
4. Make a quarter of a cup of medium white sauce, omitting the salt, and add, stirring slowly, a quarter of a cup of hot tomato juice. Season.
5. Compare the flavor of (4) with soups made by adding a saltspoon of soda to the tomato.
Give the reasons for each of the following precautions in the making of cream of tomato soup:
1. Be sure that the milk is perfectly sweet.
2. Thicken either the tomato juice or the milk. Have each hot, and do not heat further after combining; or combine cold, and heat only to the serving point.
3. Omit salt until ready to serve.
4. Pour the tomato into the milk.
5. Avoid letting the soup stand after it is made.
6. If the milk is old, or the tomato juice very acid, or the soup must stand (as in serving a large number of people), use soda.
B. Cream of Tomato Soup.
C. Prepare Lemon Milk Sherbet.
Make in large amounts in a freezer, or stir and freeze in a tin cup.
4 c. milk 11/2 c. sugar
Juice of three lemons
Combine and freeze. Curdling will not affect the quality after freezing.
The amount of fat in milk varies with the breed of cow as well as with the feed given. Milk from Jersey cows is high in fat; from Holstein cows, low. Milk from the latter breed is considered best for babies. While the amount of fat in milk averages four per cent by weight, in the cream it averages from twenty to thirty per cent. The fat of milk is already in an emulsified form, so, like the fat of egg-yolk, it is considered especially digestible. Babies, however, often have difficulty in digesting much of it. This fat is peculiar in containing a relatively high amount of the volatile fats and less olein than is present in most fats used as food. It also contains a very small amount of stearin and a fairly large amount of olein.
At least three-fourths of the protein in milk is casein. Some albumin is also present, as well as other proteins in much smaller amounts. These proteins are of high nutritive value. An unusually high percentage of them is digested and absorbed, and they do not readily undergo intestinal putrefaction. The percentage of protein in milk is much greater than in mothers' milk. To remedy this, milk for feeding to babies is diluted with water, after which more sugar is added.
Sugar of milk is the carbohydrate present in milk. This sugar is less sweet than cane and is supposed to be much better for babies, because it is less liable to irritate the stomach. As, however, cheap grades of milk sugar are impure, and the pure sugar is exceedingly expensive, many doctors recommend the addition of cane sugar to the diluted milk in baby-feeding.
The mineral elements in milk need special mention.
Calcium and phosphorus are present in unusual amounts. The iron present seems to be in a form which is most readily assimilated, thus making up somewhat for the small quantity present. Babies are born with relatively more iron in their bodies than adults have. This seems to be nature's way of assuring them a plentiful supply. Diluted cows' milk furnishes less iron than mothers' milk, and so babies which are fed artificially have other food added to their diet earlier than those which are nursed.
Boiling milk seems to bring about certain changes in the substances present. The protein is undoubtedly changed, for such milk fails to clot with rennin, while raw milk clots readily. The boiling may also affect the vitamines present. This may be an important question when milk is used as the sole food. Boiled milk does not seem to be less digestible than raw milk.
When milk sours, the lactic acid bacteria present change the milk sugar to acid. The acid finally precipitates the protein and the milk "clabbers."Milk containing too little acid to bring about this, may separate when heated. If salt is present, this is even more liable to happen. Herein lies the difficulty of making cream of tomato soup without neutralizing the acid with soda, but the flavor is superior if soda is not used.
The important thing to remember in connection with milk is its value in the diet. A reasonable amount should be included even by those living at low cost. Sherman tells us that" those who are able to spend 30 to 40 cents per person per day for food are practising true economy when they buy and use liberally the best milk obtainable, even at a price of from 15 to 20 cents per quart." Also, "in no other way can the food habits now prevailing, especially in the cities, be so certainly and economically improved as by a more liberal use of milk."
References As in the previous lesson.
1. What is meant by scalding milk? How can you easily tell when it is scalded?
2. Why is milk usually heated in a double boiler? When may this be done over a direct flame?
3. Would you infer that acid is present in chocolate, since chocolate fudge is so liable to separate in cooking? Does the separation affect the final product?
4. What two classes of condensed milk are there? How are they prepared? What do they cost? How does this cost compare with that of ordinary milk?