The chemistry of plant and animal life . tsare obtained when foods are combined so as to secure nu- RATIONAL FEEDING OF MEN 383 trients in approximately the amounts given. By meansof a careful study of the dietary, it is possible to reducethe cost of food without impairing its nutritive value,and in many cases, as the cost is decreased, the nutritivevalue is increased. 508. Chemical Changes in the Cooking of Foods.—Thechemical changes which take place in cooking are broughtabout by the joint action of heat, water and ferments andoccasionally by the use of chemicals. The various com-pounds of w
The chemistry of plant and animal life . tsare obtained when foods are combined so as to secure nu- RATIONAL FEEDING OF MEN 383 trients in approximately the amounts given. By meansof a careful study of the dietary, it is possible to reducethe cost of food without impairing its nutritive value,and in many cases, as the cost is decreased, the nutritivevalue is increased. 508. Chemical Changes in the Cooking of Foods.—Thechemical changes which take place in cooking are broughtabout by the joint action of heat, water and ferments andoccasionally by the use of chemicals. The various com-pounds of which foods are composed, namely, carbohy-drates, proteids and fats, are all susceptible to the action ofthese agencies and the chemical changes which they un-dergo are briefly discussed in Chapters XXIII and XXIV,treating of the composition of the nitrogenous and non-nitrogenous compounds. Some of the changes are phys-ical rather than chemical in character. All of the differ-ent nutrients of foods are influenced by the action of Fig. loi.—Comparative composition of raw and baked beans. Starch, in the presence of water and heat,, undergoespartial hydration, so that the material is in a condition 384 AGRICULTURAI, CHEMISTRY both chemically and mechanically to undergo readily in-version changes. In the cooking and preparation of foods,starch rarely undergoes more than the hydrationchange. In bread-making, for example, only a smallportion of the original starch is converted into solubleforms. The action of heat upon cellulose and cellular tissueis mechanical rather than chemical. The mass is partiallydisintegrated and in the case of some of the cellulose,hydration takes place to a limited extent. Human foods,however, contain comparatively little of the cellulosegroup of compounds. The sugars are partially caromel-ized by heat, provided it is sufficiently intense, but inordinary cooking operations, they undergo little or nochemical change unless associated with acids, alk
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