110 



BACTERIA AND FOOD 



is the distribution of fresh pure milk during the summer months. 

 Fresh food never contains ptomaine secretions. 



How to protect our food against decay by bacteria. It is 

 impossible to have meats, milk, vegetables, and other foods 

 absolutely free from bacteria. The most that we can do is to 

 keep our foods in such a way that the bacteria in them do not 

 develop rapidly and become numerous enough to cause imme- 

 diate decay. Absolutely fresh foods contain few bacteria, and 



if these are kept from 

 increasing, the food re- 

 mains wholesome for a 

 long time. Bacteria do 

 not grow at the freezing 

 temperature, and there- 

 fore foods kept in cold 

 storage retain their 

 freshness almost indefi- 

 nitely (Fig. 47). Meat 

 is shipped from the west 

 in refrigerator freight 

 cars, and arrives abso- 

 lutely sound and fresh 



FIG. 47. A cold storage room. Notice the t j. eastern cities 

 frost-covered pipes overhead. 



Young chickens are killed 



in the spring and kept in cold storage until the following winter, 

 when they bring high prices. The freezing temperature of cold 

 storage vaults stops the growth of bacteria. Temperatures above 

 the freezing point do not stop growth, but merely lessen the 

 rapidity of growth. The temperature of the housewife's refrig- 

 erator and the butcher's ice chest is above the freezing point, 

 and does not completely stop the growth of bacteria, which in 

 time become numerous enough to spoil the food. Meat kept 

 m cold storage at the freezing temperature remains good for 



