FOOD. 



119 



produces complete coagulation in fifteen or twenty minutes. The coagu- 

 lum is drained from the watery serum or " whey," and afterward pressed 

 into the form of cheese. The variety in consistency and flavor of differ- 

 ent cheeses depends mainly on the proportion of fatty matter retained in 

 the coagulum, and upon certain slow changes, in the nature of fermen- 

 tations, which go on in it subsequently. 



The fatty matter of milk is suspended in the serous portion under the 

 form of minute spheroidal masses. These little masses or " milk-glob- 

 ules" are not quite fluid at ordinary temperatures, but have a semi-solid 

 consistency owing to their containing a considerable proportion of pal- 

 mitine. The fat globules, separated by churning from the other ingre- 

 dients of the milk, and made to unite into a coherent mass, constitute 

 butter. This substance, accordingly, represents simply the oleaginous 

 ingredients of the milk ; and when purified from the watery portions 

 entangled with it, consists mainly of palmitine and oleine, together 

 with a small proportion of peculiar odoriferous and flavoring ingredi- 

 ents, the principal of which has received the name of " butyrine." These 

 substances are usually mingled in the following proportions : 



Palmitine 68 parts. 



Oleine 30 " 



Butyrine and other flavoring matters . . . 2 " 



100 



When well prepared and in good condition, butter constitutes one of 

 the most valuable and easily assimilated forms of oleaginous food. If 

 contaminated with the remains of the nitrogenous matter of the milk, 

 its fatty ingredients after a time become decomposed with the develop- 

 ment of volatile fatty acids ; in which condition the butter is said to be 

 " rancid," and is no longer fit for food. 



Bread. The cereal grains resemble each other more or less in their 

 constitution, all of them containing starch, nitrogenous matter, dextrine 

 or sugar, fat, and mineral salts in various proportions. Wheat is dis- 

 tinguished from the remainder in containing a considerably larger quan- 

 tity of nitrogenous matter as compared with the other ingredients, and 

 in the peculiarly adhesive or fibrinous quality of this substance, which 

 has received accordingly the name of " gluten." The different grains 

 in common use for food have when dry the following average compo- 

 sition, according to Payen. 



COMPOSITION OF THE CEREAL GRAINS. 



