BREAD, CAKES, ETC.] 



CHEMISTRY. 



345 



the stable, manure effects in the field ; and while witl 

 cattle an abundant formation of fat is principally sought, 

 the chief endeavours of the agriculturist are directed to 

 the production of gluten. The greater the amount o: 

 nitrogen incorporated into the soil by means of manure 

 in the form of ammonia, the more considerable is the 

 yield of gluten, which by means of the seeds of the 

 cerealia renews the blood of man. 



Besides manure, the temperature exercises a most im- 

 portant influence upon the quantity of gluten produced 

 by the gramineous plants of the fields. In summer, and 

 in warm climates, more gluten is formed than in the corn 

 of winter and of the rough north. 



52. Constituents of Bread. Although bread is made 

 of different cereals in different countries as of rice by 

 the Hindoos, and of maize in Tyrol and at the Gold- 

 coast wheat and rye furnish the flour chiefly used in 

 the preparation of bread in Europe. 



Our ordinary bread is prepared with leaven, and is, 

 therefore, called leavened or fermented bread. Leaven 

 is nothing else than a part of the common dough pre- 

 served until the next baking, during which time it has 

 become sour. By the process of fermentation in this 

 preserved doiigh, lactic and acetic acids are formed. 

 t may be substituted for leaven with precisely the 

 same effect. In both, an albuminous compound is the 

 occasion of the sugar formed in the dough turning it into 

 a Vinous fermentation. By this process the sugar is 

 decomposed into alcohol, which evaporates, and into 

 carbonic acid, which, inclosed by the tough gluten, is 

 retains! in the bread. 



P'lour, the lerment water, and salt, form the dough. 

 In this a part of the starch has already been transformed 

 into sugar ; and by the action of leaven or yeast, this 

 sugar is transmuted into alcohol and carbonic acid. The 

 carbonic acid, which is prevented from escaping by the 

 tenacity of the gluten, produces the vesicles which give 

 to the bread its ordinary lightness. By the process of 

 baking, a portion of the starch in the external layer of 

 the bread is transformed into gum and sugar. The 

 soluble albumen coagulates the process; the alcohol 

 evaporates. 



By exposure to heat, this crust becomes brown ; a 

 compound of an agreeable bitter taste is thus formed, 

 similar to that produced by the roasting of different other 

 organic compounds. This peculiar bitter principle is 

 called "roast-bitter," or "Assamar." Bread is so 

 easily soluble in water, that it is liquefied even by the 

 humidity of the air. 



Good wheaten bread is white ; the real brown bread, 

 as, for example, the well-known Westphalia rye bread 

 called " Pumpernickel," is from rye. As wheaten flour 

 contains more gluten than rye flour, the same proportion 

 is not found in white and brown bread ; and as it is 

 gluten which causes the sugar to undergo fermentation 

 and retain the carbonic acid, the reason is apparent why 

 rye bread, which contains a smaller proportion of gluten, 

 is less spongy than wheaten bread. Stale bread is 

 scarcely drier than fresh. In five days fresh bread loses 

 one-hundredth only of its amount of water, and becomes 

 stale even if it has cooled in an atmosphere saturated 

 with moisture. But stale bread may bo retransformed 

 into fresh if put again into the oven, whereby a con- 

 siderable amount of water is necessarily lost. Both high 

 and low temperatures cause a change in the smallest 

 particles, which has yet more closely to be investigated 

 by science. It is, however, a fact, that stale bread is 

 hard and firm, but not dry. 



53. Nutritive Qualities of Bread. Bread is not, on 

 the whole, so nutritious as meat, so far as the albuminous 

 substances are concerned ; for even the richest bread 

 contains only about two-thirds of the quantity of albu- 

 minous matters present in beef. 



The digestibility, moreover, of bread and flesh is not 

 to be considered equal ; for gluten is more difficult of 

 nolution by our digestive juices than the fibres of the 

 muscles, and corresponds less intimately with the albu- 

 minous substances of the blood ; therefore it is more 

 lowly transformed into its constituents. 



The starch, so abundant in bread, has to be trans- 

 formed into fat. The inferior solubility peculiar to the 

 ready-formed fat of the flesh is thus compensated. 



Of the fat which the excretions subtract from the 

 blood, bread is a much more productive source than 

 meat ; for more than one-third of wheaten bread con- 

 sists of starch ; while one-tenth in weight of gum, and a 

 small quantity of sugar, is also contained in it. This 

 predominance of the constituents of fat, explains why 

 bread contains much more of solid substance than flesh. 

 In the former, the proportion of water scarcely amounts 

 to one-third of the whole. 



This abundance of the constituents of fat does not at 

 all correspond in proportion to the small quantity of fat 

 to be found in the blood ; and in comparing the nutri- 

 tiveness of flesh with that of bread, we must, therefore, 

 decide in favour of the former. 



The nutritiveness of the different kinds of grain is de- 

 pendent upon their comparative proportions of gluten ; 

 for in all of them the constituents of fat are present in 

 abundance. Wheat, rye, oats, barley, rice, and maize, 

 form a series, in which wheat takes the highest, and 

 maize the lowest place with respect to nutritiveuuss. 

 Thus in rice and maize there is scarcely to be found 

 one-seventh of the amount of gluten contained in wheat. 

 A corresponding proportion of nutritiveness consequently 

 exists in the bread prepared of these different kinds of 

 grain. Chemical knowledge thus justifies the old usage 

 which prefers wheat and rye-bread to all other kinds of 

 bread. 



54. Indujestibility of Cakes. Like stewed hare, or 

 any other composite preparation of meat, cakes belong 

 more to a cookery-book than to a treatise on food. 

 Eggs, fat, sugar, different condiments, almonds, dry 

 or fresh fruit, are mixed with the dough of different 

 kinds of flour ; and all these constituents will be spoken 

 of in their respective places. Why are cakes less con- 

 ducive to health than bread ? This question is so im- 

 portant to that large class of housewives who are proud 

 of their pastries, that I will not pass it without a reply. 



Sugar is the constituent considered, by most people, 

 the most dangerous, while it is in reality the least so. 

 [f not added in too great a quantity to cakes and tarts, 

 sugar is transformed into lactic acid, and assists the 

 stomach in digesting. It is the fat, so abundantly mixed 

 with many tarts in the form of butter, and as a consti- 

 ;uent of the eggs and almonds, which renders many 

 duds of pastry so difficult of digestion. The more these 

 'ats are transformed by heat into the products of their 

 respective decomposition, the more will this be the case. 

 For this reason, macaroons, almond-tarts, or chocolate- 

 cakes, containing the fat of cocoa, are more indigestible 

 ,han other fruit-cakes and pastry which contain neither 

 almonds nor cocoa. 



The indigestibility of the latter, however, corresponds 

 exactly to the quantity of butter and yolks of eggs used 

 n their preparation ; for in the yolk the fat of the eggs 

 s principally to be found. Cakes, therefore, containing 

 only a small proportion of butter and eggs, are the most 

 'nnoxious. 



The roast-bitter, produced by baking, in the crust of 

 >read, originates in all farinaceous food in the same way. 

 .t is the substance which principally takes up water from 

 .he air, or the interior of the cakes, and causes the crust 

 o be moist. 



But why are cakes preserved in a moister condition, 



hen kept in tin boxes secluded from the air 1 Because 



n a closed place the water of the cake evaporates less, 



and the cake therefore is less desiccated. The sugar, 



with which the surface is usually sprinkled, and the 



oast-bitter principle, attract the water from the interior 



)f the cake ; and after a time the sugar is found melted, 



and the crust humid. 



55. Peas, Beans,, and Lintels. Peas, beans, and 

 intels are comprised under the name of leguminous 

 ueds. If we wished to divide all aliments into two 

 irincipal groups, the former containing those of a 

 ligher nutritive quality, we should in this class the 

 eguminous seeds together with meat and bread. For 



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