Milk is probably the most important article of diet used today, because of the large place it fills not only in the diet of children and invalids but also in the economic and hygienic nutrition of healthy adults.

In qualitative composition milk is an aqueous solution of milk sugar, mineral matter, and albumin with fat globules held in suspension and casein together with mineral matter in a state of semi-solution. Other facts regarding the constituents of milk will be developed in the course of the experimental work included in this chapter.

The quantities of the chief constituents average approximately as follows: water, 87 per cent; milk sugar, 5 per cent; fat, 4 per cent; proteins, 3.3 per cent; ash, 0.7 per cent. Market milk may of course be somewhat less rich in one or more of the foodstuffs than this average, but nearly every state now has legal requirements governing the milk industry and setting at least a minimum standard for the product. In buying milk the sanitary quality should be carefully considered as well as the food value. See Leach's Food Inspection and Analysis, Chapter VII (Cheese), Rosenau's The Milk Question, and Sherman's Food Products, Chapter III (Canning And Preserving).

Milk is the most important of all foods as a source of bodybuilding material for growing children. While the great economic growth of the milk industry, the progress in the chemical and bacteriological study of milk, and the care given to the legal and sanitary control of the production and handling of milk are all indications of a growing realization of the importance of milk as a food, yet it is of interest to find that the great quantity of milk used as such in this country amounts on calculation to only a little over a half a pint per day for every man, woman, and child, whereas the study of dietetics teaches us that adults should have at least as much milk as this and children a good deal more - "a quart of milk a day for every child" if possible. The study of milk cookery should therefore have as one of its main objects the development of a higher appreciation of milk as a food and the encouragement of its more liberal use in the diet, both as a beverage and in the greatest variety of cooked foods.

Experiments On Milk And Milk Products

Cream

83. - Examine a bottle of milk obtained from a reliable dealer.

a. Read the statements on the cap.

b. Of what significance are they?

c. What are the two layers in the bottle ?

d. Why is the yellow layer at the top ?

84. - a. Examine with the microscope a tiny drop of cream.

b. Make a drawing of the fat droplets.

85. - a. Divide a quart of cream into four cups: A, B, C, D.

b. Heat A in a double boiler until a thick scum appears. Allow the cream to cool and then beat it with a Dover egg beater. (Keep B, C, and D for subsequent experiments.) c. Can this cream be beaten stiff ?

d. What was the scum which appeared when the cream was heated ?

86. - a. Whip B with a wire whisk until stiff.

b. Beat c with a Dover egg beater until stiff.

1 A division in the recipes for milk and cheese has been made, but the experiments for milk and milk products have been considered together for purposes of comparison and summary.

c. Compare A, B, and C as to flavor, consistency, and volume.

d. How do you explain differences noted ?

87. - Beat D with a Dover egg beater until fat globules form masses and butter results. Drain off buttermilk and save for further experiments.

Compute the per cent of butter obtained from a unit of cream.

88. - Wash the butter in cold water until no more buttermilk appears. "Pat" out the water.

a. Weigh the washed butter and divide it into two parts of equal weight.

b. Add sufficient salt to one part to give it the usual salty flavor.

c. Put both parts in the refrigerator for a few hours to ripen.

d. Compare as to weight, flavor, and texture.