Elements of the theory and practice of cookery

What else does food do for us? Breathe on your fingers; your breath is warm. Evidently heat is pro- duced in the body. 131. The body compared to a steam-engine. — Just as heat and mechanic power are produced by burning fuel under the boiler of a steam-engine, so force and heat are produced by the oxidation of food in the tissues of the body.i Starch slowly oxidized in the body gives off just as much heat and force as if burnt (z.e. rapidly oxidized) in the air. How is oxygen taken into the body? What combustible elements does starch con- tain? What other kinds of slow oxidation do you know of? (§§ 68 and 103.) Thus food serves as fuel to warm the body and to keep its machinery running, its oxidation, as in the case of other fuels, giving rise to carbon dioxide, water, and also to waste products corresponding to the ash of coal or wood. 132. The body, unlike an engine, repairs itself. — A steam-engine differs from the body, however, in one important respect, — it cannot repair itself. No fuel we 1 About one-third of the energy contained in the food we eat can be utilized in productive work; the other two-thirds is used up inter- nally in life processes. FUEL FOODS: SOME STARCHY PLANTS 73 can feed it with will stop a leak in the boiler or restore a missing rivet ; but food renews the tissues of the body as fast as they wear out, making bone, nerve, muscle, and skin for us continually. Then, too, in a steam- engine, fuel and air meet and unite in one place, whereas in the body combustion goes on in all its parts. 133. Different kinds of foodstuffs serve the body in different ways ; for instance, starch cannot build tissue, but is efficient, first, as a force-producer, sec- ondly, as a heat-giver. Fat and oil have greater fuel value than starch has, because they contain a much smaller proportion of oxygen and so can unite with more. Experiment. — Throw a bit of butter or lard and a bit of starch into the fire. AVhich burns best ? Chemists are able to calculate exactly how much work a certain amount of starch or of other food will enable a man to do. Other kinds of starch and the manufacture of starch are de- scribed on p. 248 of Food Products of the World. Repeat at home the experiments given in this section. Section 3. Cereals; Simple Cereal Poods On either side the river lie Long fields of barley and of rye That clothe the wold and meet the sky. — Tennyson. 134. Cereals, or grains, are grasses the seeds of which are used for food ; among the most important 74 THEORY AND PRACTICE OF COOKERY being wheat, Indian-corn or maize, oats, rice, rye, and barley. From these are prepared various breakfast foods, — oatmeal, wheatena, and others, besides corn- meal and other preparations sometimes served for breakfast. 135. Cereals compared with potatoes. — Cereals, like potatoes, contain starch. How may we prove this? If they were like potatoes in other respects, they could be cooked in much the same way. Unlike potatoes, however, they do not contain nearly enough water to soften the starch, and must, therefore, be so cooked that they can absorb more. All except rice contain much woody fibre tougher tlian that in potatoes, and so need longer cooking.