VEGETABLE FOODS. 



427 





It is remarkable that in white wheat sodium is wanting and is replaced by 

 other alkalies. Rye contains more cellulose and dextrin than wheat, but less 

 sugar. Rye-bread is, as a rule, less porous. Barley and oats are much used as 

 gruel, and in the North also mixed in bread. 



Oats contain a crystalline globulin (avenalin) , and a proteid soluble in alcohol 

 and another soluble in alkalies. By admixture with water or neutral salts three 

 other proteids are obtained as products of transformation. Rye and wheat 

 yield one globulin (edestin) ; one albumin (leukosin) ; gliadin, forming gluten, 

 and soluble in dilute alcohol; and glutenin (absent from rye), soluble in dilute 

 acids and alkalies. Barley contains leukosin, edestin, hordein, corresponding to 

 gliadin, and also other proteids. 



In the preparation of bread, flour is kneaded, together with water, to form 

 dough, in which the gluten acts as a cementing substance, and to which salt and 

 also yeast (saccharomyces cerevisiae) are added. Under the influence of heat the 

 albuminates of the flour begin to undergo decomposition and the ferments act 

 upon the swollen starch, which is partially transformed into sugar. The sugar 

 undergoes further decomposition into carbon dioxid and alcohol, of which the 

 first, forming bubbles in the stiff dough, causes this to become spongy. Certain 

 bacteria also cooperate with the yeast to the same end. By the baking at 200 

 C. the alcohol is driven off and the dough is done. Much readily soluble dextrin 

 is formed in the crust . In the 

 preparation of sour bread, old 

 sour dough, in which the sugar 

 has partially undergone lactic- 

 acid fermentation, is added 

 instead of yeast, and as a re- 

 sult, in addition to the alco- 

 holic fermentation, the lactic- 

 acid fermentation of the 

 grape-sugar in the dough is 

 also initiated. As in the 

 transformation of starch into 

 sugar, and the latter into car- 

 bon dioxid and alcohol 

 (which eventually escape) , 

 material is directly lost; am- 

 monium carbonate, which es- 

 capes during the process of 

 baking with the expansion of 

 the dough, is added. This 

 loss amounts to about one 

 per cent.; with an average 

 daily consumption of bread 

 for each individual of 256 

 grams, the daily loss for 1,000,000 persons should equal 2500 kilograms of bread, 

 or sufficient for 10,000 persons. J. v. Liebig proposes the use of sodium bicarbon- 

 ate and hydrochloric acid for the same purpose ; then the dough will not have to 

 be salted, because of the formation of sodium chlorid. Horsford's baking-powder 

 (calcium phosphate and sodium bicarbonate) is also used. It permits the escape 

 from the dough of the expanding carbon dioxid, the phosphoric acid of which is 

 also useful to the body. 



The legumes contain much albumin. Beans contain two globulins readily 

 soluble in salt-solutions the phaseolin of Ritthausen and phaselin. Peas and 

 vetches yield in considerable amount a globulin, designated legumin by Braconnot, 

 which is soluble in a solution of sodium chlorid, and also three other proteids. 

 Legumes contain also starch, lecithin, and cholesterin, together with from 9 to 

 19 per cent, of water. Peas contain 28.02 per cent, of albumin and 38.81 of starch; 

 beans 28.54 and 37.50; lentils 29.31 and 40 respectively. The last are richer in 

 cellulose. Because of the deficiency in gluten no dough can be made from them, 

 and therefore no bread. As a food for the mass of the people, these plants deserve 

 the greatest consideration, because of the large amount of albumin they contain, 

 although they may be a source of intestinal discomfort in consequence of the devel- 

 opment of gas, as well as of the presence of indigestible cellulose. Leguminous 

 flour, when mixed in different proportions with the flour of cereals (for instance 

 in the form of Hartenstein's leguminose) , can be used with advantage in the feed- 

 ing of children and debilitated persons. 



FIG. 138. Section through a Grain of Wheat: p, epidermis, with 

 c, cuticula, m middle layer, qu transverse, sch tubular cells, br 

 and n seed-membrane, Kl gluten, / starch. 



