CH. XXX.] BKEAD 489 



Bread. 



Bread is made by cooking the dough of wheat flour mixed with 

 yeast, salt, and flavouring materials. An enzyme in the flour acts at 

 the commencement of the process, when the temperature is kept a 

 little over that of the body, and forms dextrin and sugar from the 

 starch, and then the alcoholic fermentation, due to the action of the 

 yeast, begins. The bubbles of carbonic acid, burrowing passages 

 through the bread, make it light and spongy. This enables the 

 digestive juices subsequently to soak into it readily and affect all 

 parts of it. In the later stages, viz., baking, the temperature is raised, 

 the gas and alcohol are expelled from the bread, the yeast is killed, 

 and a crust forms from the drying of the outer portions of the dough. 



White bread contains, in 100 parts, 8 to 10 of protein, 55 of 

 carbohydrates, 1 of fat, 2 of salts, and the rest water. 



Cooking of Pood. 



The cooking of foods is a development of civilisation, and serves 

 many useful ends : 



1. It destroys all parasites and danger of infection. This relates 

 not only to bacterial growths, but also to larger parasites, such as 

 tapeworms and trichinae. 



2. In the case of vegetable foods it breaks up the starch grains, 

 bursting the cellulose and allowing the digestive juices to ome into 

 contact with the granulose. 



3. In the case of animal foods it converts the insoluble collagen of 

 the universally distributed connective tissues into the soluble gelatin. 

 The loosening of the fibres is assisted by the formation of steam 

 between them. By thus loosening the binding material, the more 

 important elements of the food, such as muscular fibres, are rendered 

 accessible to the gastric and other juices. Meat before it is cooked is 

 generally kept a certain length of time to allow rigor mortis to pass off. 



Of the two chief methods of cooking, roasting and boiling, the 

 former is the more economical, as by its means the meat is first sur- 

 rounded with a coat .of coagulated protein on its exterior, which keeps 

 in the juices to a great extent, letting little else escape but the drip- 

 ping (fat). Whereas in boiling, unless both bouillon and bouilli are used, 

 there is considerable waste. Cooking, especially boiling, renders the 

 proteins more insoluble than they are in the raw state ; but this is 

 counterbalanced by the other advantages that cooking possesses. 



In making beef tea and similar extracts of meat it is necessary 

 that the meat should be placed in cold water, and this is gradually 

 and carefully warmed. In boiling a joint it is usual to put the meat 

 into boiling water at once, so that the outer part is coagulated, and 

 the loss of material minimised. 



