

PRESERVATION OF FOOD PRODUCTS FROM BACTERIA. 321 



he pleases, and that part of his product for which he does not 

 find an immediate market may be preserved for a later season 

 by the process of canning. It is well for the agriculturist to 

 learn that in farming, as in all other industries, it is the special- 

 ist who succeeds, and that the proper utilization of this process 

 of canning is one of the means of making a special product 

 upon a farm yield proper returns. 



A few practical points connected with the process of can- 

 ning are of interest and may sometimes be of use to the agricul- 

 turist. It is one of the unfortunate facts connected with this 

 industry that not all of the cans of food thus prepared result 

 successfully. Many of the cans of tomatoes, and a still larger 

 number of cans of corn, even after careful treatment and thor- 

 ough sealing, undergo some of the putrefactive changes which 

 it is the purpose of the canning to prevent. Cans of corn 

 thus fermented become swollen from the pressure of the gases 

 which accumulate within, and the contents are ruined. Such 

 spoiling of the material must be due, either to the fact that the 

 original heat was insufficient to destroy all the bacteria, or due 

 to a secondary contamination. In most cases the chance of 

 secondary contamination is practically ruled out by the con- 

 ditions ; and the cause of the trouble is, in nearly all cases, 

 that some of the organisms in the original product have re- 

 sisted the heat. This is a very natural suggestion when we 

 remember two facts : that many bacterial spores resist the tem- 

 perature of boiling for a long time without injury, and that in 

 order to prevent subsequent decay every individual spore must 

 be destroyed. If there is left in the can, after sealing, a single 

 resisting spore, it is just as bad as if there were a million ; for 

 this one is capable of completely ruining the product in the 

 course of time. If, therefore, the fruit chances to have some of 

 these highly resistant spores clinging to it, it may very well 

 happen that, occasionally, some of them will not be killed by 

 the heat of the boiling. It follows, of course, from this that 

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