126 PHYSIOLOGICAL CHEMISTRY. 



acquired by bread is the main object of its fermentation, although an 

 agreeable flavor is also developed by the process, which does not exist 

 in unfermented bread. The interior of the loaf, in baking, does not 

 rise above 100 C. ; the exterior, which is subjected to a higher tem- 

 perature, becomes covered with a crust of partially torrefied starch or 

 dextrine, and caramelized sugar. The interior of the loaf also usually 

 retains a little glucose, not destroyed in the process of fermentation. 

 A considerable portion of the water which was mixed with the flour 

 remains united with its organic ingredients; so that 100 parts of flour 

 will usually yield, after baking, 130 parts, by weight, of bread. 



Wheaten bread thus prepared has the following average composition : 



COMPOSITION OF WHEATEN BREAD. 

 Starchy matters (starch, dextrine, glucose) . . . 56.7 



Albuminous matter (gluten, etc.) 7.0 



Fatty matter 1.3 



Mineral matter (calcareous, magnesian, and alkaline salts) 1.0 



Water 34.0 



100.0 



Thus, while bread contains an abundance of albuminous and starchy 

 matter, it is deficient in fat ; and instinct leads us to take with it butter, 

 fat bacon, or some other form of oleaginous food. 



The good quality of bread, aside from that of the flour from which 

 it is made, depends mainly on the process of fermentation. If this be 

 incomplete, the bread is heavy, and not sufficiently reticulated in texture. 

 If too long continued, it passes into an acid fermentation, and develops 

 a sour taste. When properly fermented, the bread is uniformly light 

 and spongy, and has no acid reaction. 



Meat. The muscular flesh of various animals affords the most valu- 

 able and nutritious kinds of food, among which beef, mutton, and venison 

 hold the highest place. The muscular fibre itself consists almost exclu- 

 sively of nitrogenous matters, but in point of fact the flesh used for 

 food is always accompanied with more or less adipose tissue, and even 

 when freed from visible fat, it always contains, according to Payen 

 and Pavy, more or less oleaginous matter entangled with its fibres. In 

 various kinds of meat, and even in that from different parts of the same 

 animal, the proportion of fat will vary considerably ; but it was found 

 by Pavy, in one of the best and most commonly used portions of beef, 

 to amount to about 5 per cent, of the whole. 



COMPOSITION OF BEEF FLESH. 



Water 77.5 



Albuminous matter 16.0 



Fat 5.0 



Mineral salts 1.5 



100.0 



The mineral matters consist of alkaline chlorides and phosphates, 

 with phosphates of lime and magnesia. 



