The new century cookery book

Extractives. — This is the term given to the group of chemical substances which we can dissolve out of any substance by water or other solvent. Soups, extracts of meat, glaze and similar pre- parations mainly consist of these substances. Finally there is a large group of more or less desirable accessories to food, such as spices and condiments, wines, tea, coffee, and cocoa, and so on. Having thus considered very briefly these ‘ proximate principles,’ let us see how a few of the more ordinary articles of diet supply us with them. 1. Milk.- -This naturally comes first, inasmuch as it is the most complete of any of the natural food stuffs. It contains : — A. Proteids, mainly a proteid called caseinogen. — This is dissolved in the milk, but unlike most proteids does not coagulate in boiling. When, however, a little rennet is added to the milk, it becomes converted into casein, and entangling with it the fatty globules of the milk, forms the well-known curd. This forms the principal constituent of cheese. If milk be allowed to boil for some time, certain changes occur, the exact nature of which has not been discovered. They are of great practical importance from the fact that children fed upon milk prepared in this way frequently do not thrive. Milk should therefore be removed from the fire immediately it begins to boil, especially if it is to be used for feeding very young children. B. Fats.— If a drop of milk be examined under the microscope, it is seen to consist of numerous globules of fat which, when shaken together, form butter, one of the most valuable of all the fats from a physiological standpoint. C. Carbohydrates. — Milk contains a special form of sugar lactose, or milk sugar. D. Water, Salts and Extractives. Human milk differs from cow’s milk in that it contains more sugar and less proteid matter. In round numbers the relative quantities are : — ^ — Human Milk Cow’S- Milk Proteid (per cent.) . • • ' . . ! 2 4 Fat (per cent.) . . i 4 4 Carbohydrate (per cent.) . ' 4 THE SCIENCE OF COOKERY 19 2. Meat.-— Here we have to consider two distinct structures. In the first place, we have the actual fibres of the meat, consisting, besides water, almost entirely of proteid, or albuminous material of several varieties. Some of these after death undergo coagulation, causing the carcase of the animal to become stiff and rigid. The other constituents of the meat are sinews and material uniting the fibres together. These contain fat and a substance which yields gelatin on boiling with water. Gelatin, the chief constituent of jellies and clear soups, is a sub- stance allied to proteid, and is of value in that it can replace part, though not all, of the proteid part of the diet. It has hence been called a ‘ proteid sparing ’ food. 3. Eggs. — These form the nearest approach to a pure proteid that we have in nature, their other constituents being comparatively unimportant. 4. Bread and Flour. — These in various forms constitute the main sources of carbohydrates. Bread contains a large amount of starch, some sugar formed from it in the process of baking, as well as about 8 per cent, of the vegetable proteid called gluten. Bread is made ‘ light ’ by the action of yeast, a small plant which, as it grows, forms carbonic acid gas from the sugar. This gas bubbling through the dough renders it porous.