154 CEREALS. 



The proteids of oats are three in number : One soluble in 

 alcohol, one a globulin, and the third a proteid soluble in alkali. 



Jn maize there are two globulins, one a vitellin and the other 

 a myosin ; one or more albumins ; and zein, a proteid soluble in 

 alcohol. 



The proteids of rye are gliadin, leucosin, edestin, and proteose ; 

 and those of barley are leukosin, proteose, edestin, and hordein. 



The cereal most commonly used is, perhaps, wheat, the flour 

 of which is made into bread. 



Bread. The cereal most used for bread-making is wheat, 

 though bread is also made from rye and cornmeal. Wheat-flour 

 contains approximately 14 per cent, of water, 12 of proteids, and 

 70 of carbohydrates. The amount of fat and salts is small. In 

 the making of flour the wheat-grains are ground, and the result 

 is sifted, or " bolted " as it is termed, into fine flour, coarse flour, 

 and bran. The bran is the extreme outer covering of the grain, 

 and is so tough and silicious that it is of no nutritive value, while 

 the other coverings contain so much of proteid, fat, and salts as to 

 give them considerable food-value. The process of making flour 

 just described is known as the old process, and results in heating 

 the flour, which, if not properly cooled, is liable to spoil. In the 

 new process the grains are cut with knives or crushed between iron 

 rollers which do not produce heat. Flour is made by another 

 process, in which the grains are moistened and the extreme outer 

 covering or husks removed by rubbing. The grains after being 

 dried are exposed to blasts of air which have force enough to thor- 

 oughly disintegrate them. When pulverized this is known as 

 whole-wheat flour, and contains all that is nutritive in the wheat. 

 In making bread the flour is moistened with water or .milk to 

 which yeast has been added, and when thoroughly mixed this 

 becomes dough. Salt is also added, and some breadmakers add 

 sugar and butter as well. After thorough kneading, the dough is 

 exposed to a temperature of about 24 C. The starch is con- 

 verted by an enzyme which exists in the wheat into dextrin and 

 sugar, and this, under the influence of the yeast, then undergoes 

 the alcoholic fermentation, alcohol and carbonic-acid gas resulting. 

 This gas rises up through the dough, expanding it to more than 

 double its original volume, making it thereby very spongy. When 

 the dough has risen sufficiently, it is put into an oven and baked. 

 This results in killing the yeast-cells, and thus prevents any 

 further fermentation, and at the same time the carbonic acid and 

 alcohol are expelled and the crust is formed. Wheat bread con- 

 tains 7 to 10 per cent, of proteids, 55 of carbohydrates, 1 of fat. 

 2 of salts, and 32 to 35 of water. 



