FOODS 59 



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. During baking 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, 7 to 10 of protein, 55 of carbo- 

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



COOKING OF FOOD 



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

 relating to this subject is a matter of education and taste rather than 

 of physiological necessity. Cooking, however, 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 come into 

 contact with 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 

 surrounded with a coat of coagulated protein on its exterior, which 

 keeps in the juices to a great extent, letting little else escape than 

 the dripping (fat). Whereas in boiling, unless 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. 



Beef Tea. 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 cooking a joint it is usual to 



