434 Bacteria in Relation to Country Life 



The canning industries have been responsible for the 

 growth of skill and intelligence in many farming com- 

 munities, and have, thereby, contributed much toward 

 the development of American agriculture. They have 

 benefited both the producer and the consumer and have 

 indirectly affected the growth and prosperity of other 

 important industries, notably the manufacture of tin- 

 cans, of glassware, and of fertilizers. 



Losses through imperfect canning. — Occasionally, the 

 elimination of the bacteria from the canned goods is not 

 complete. Spores of resistant species survive the heating 

 process, develop later, and spoil the contents of the 

 package. Such spoiled packages frequently burst on 

 account of the accumulation of gas in the cans, or merely 

 bulge outward. They are designated as "swells" at 

 the canneries, and their contents, on opening, are found 

 to be decomposed and offensive to the smell. In other 

 instances, the imperfectly sterilized cans do not swell, 

 but the bacteria within them cause the souring of the 

 material. The losses thus occasioned to the canneries 

 are, at times, considerable. Entire shipments are now 

 and then rendered worthless. This involves not only a 

 direct monetary loss, but, also, that of reputation, since 

 the swelling does not become apparent, at times, until 

 after the goods are in the hands of the jobber or of the 

 retailer. 



Temperatures required for sterilization. — Some fruits 

 or vegetables requii'e higher temperatures than others. 

 For instance, pie-plant will keep with less heating than 

 is required for asparagus, a difference ascribed to the 

 acid in pie-plant. Again, the heat does not pass so readily 



