386 AGRICULTURAL CHEMISTRY 



less digestible after the action of prolonged heat. Ex- 

 periments in the feeding of animals have shown that when 

 foods are cooked, the total digestibility of the nutrients 

 is not increased, and in some cases, a smaller amount of 

 nutrients was absorbed after cooking than before. This 

 does not mean that the cooking of foods is undesirable 

 because ease of digestion is equally as important as com- 

 pleteness of digestion. Also cooking sterilizes the food, 

 which is desirable. Many foods, if consumed uncooked, 

 would be unwholesome because of the presence of ferment 

 bodies or poisonous compounds as ptomains. When 

 acted upon by heat, the ferment bodies are destroyed and 

 the ptomain compounds decomposed. 



When salt, soda and other chemicals are used, chem- 

 ical changes, to a limited extent, take place. Soda, for 

 example, combines with the proteid compounds, forming 

 alkali proteids and the acids form acid proteids. In 

 cooking and preparing foods, many of the physical 

 changes which take place precede and are necessary to the 

 chemical changes. In the boiling of potatoes, for exam- 

 ple, heat changes the physical character of the cells but 

 does not alter the solubility of the starch. The albumin 

 is coagulated and small amounts of the mineral com- 

 pounds and other bodies are extracted. In the cooking 

 of some of the cereals, as oatmeal, if the process is con- 

 tinued for only a few minutes, the starch is not acted 

 upon to any appreciable extent because of the relatively 

 large amount of gelatinous proteids which protect the 

 starch particles. If the cooking is continued for three 

 or four hours, the material is disintegrated, the starch 



