VEGETABLE FOODS. 



351 



1. The cereals are most important vegetable foods ; they contain proteids, starch, 

 salts, and water about 14 per cent. The nitrogenous body glutin is most abundant 

 under the husk (fig. 236, c). The use of whole meal containing the outer layers 

 of the grain is highly nutritive, but bread containing much bran is somewhat indi- 

 gestible (Rubner). Their composition is the following : 



It is curious to observe that soda is absent from white wheat, its place being taken by other 

 alkalies. Rye contains more cellulose and dextrin than wheat, but less sugar ; rye-bread is 

 usually less porous. 



[Oatmeal contains more nitrogenous substances (gliadin and glutin-casein) than wheaten flour, 

 but owing to the want of adhesive properties it cannot be made into bread. The amount of fat 

 and salts is large.] 



In the preparation of bread the meal is kneaded with water until dough is formed, and to 

 it is added salt and yeast (Saccharomycetes cerevisise). When placed in a warm oven, the pro- 

 teids of the meal begin to decompose and 

 act as a ferment upon the swollen-up starch, 

 which becomes in part changed into sugar. 

 The sugar is further decomposed into C0 2 

 and alcohol, the C0 2 forms bubbles, which 

 cause the bread to "rise " and thus become 

 spongy and porous. The alcohol is driven 

 off by the baking (200), while much soluble 

 dextrin is formed in the crust of the bread. 

 [But C0 2 may be set free within the dough 

 by chemical means without yeast or leaven, 

 thus forming unfermented bread. This 

 is done by mixing with the dough an 

 alkaline carbonate and then adding an acid. Fig. 236. 



Baking powders consist of carbonate of Microscopic characters of wheat ( x 200). , cells of 

 soda and tartaric acid. In Daughsh's pro- the bran ; b, cells of thin cuticle ; c, glutin cells ; 

 cess for aerated bread, the C0 2 is forced d starch cells, 

 into water, and a dough is made with this 



water under pressure, and when the dough is heated, the C0 2 expands and forms the spongy 

 bread. Bread as an article of food is deficient in N, while it is poor in fats and some salts. 

 Hence the necessity for using some form of fat with it (butter or bacon). 



2. The pulses contain much albumin, especially legumin : together with starch, 

 lecithin, cholesterin, and 9 to 19 per cent, water. Peas contain 18*02 proteids, and 

 34 - 81 starch : beans 28*54, and 37*50 : lentils, 29*31, and 40, and more cellulose. 

 Owing to the absence of glutin they do not form dough, and bread cannot be pre- 

 pared from them. On account of the large amount of proteids which they contain, 

 they are admirably adapted as food for the poorer classes. 



[3. The whole group of farinaceous substances used as "pudding stuffs," such as corn-flour, 

 arrow-root, rice, hominy, are really very largely composed of starchy. substances.] 



4. Potatoes contain 70 to 81 per cent, water. In the fresh juicy cellular tissue, 

 which has an acid reaction, from the presence of phosphoric, malic, and hydro- 

 chloric acids, there is 16 to 23 per cent, of starch, 2*5 soluble albumin, globulin, 

 and a trace of asparagin. The envelopes of the cells swell up by boiling, and are 

 changed into sugar and gums by dilute acids. The poisonous solanin occurs in the 

 sprouts. In 100 parts of potato ash, May found 49*96 potash, 2*41 sodium chloride, 



