1/8 BACTERIA, YEASTS, AND MOLDS 



its contents, is placed in a convenient heating appa- 

 ratus for thorough sterilization, the opening in the top 

 being sufficient for the exit of steam and for preventing 

 internal pressure, which might give rise to an explosion. 

 In some factories it is sometimes customary to heat the 

 product in a bath of CaCl, which makes it possible to 

 obtain a temperature of 260° — quite sufficient to sterilize 

 the contents of the can, even though it contain resisting 

 spores,- as will be the case with peas or corn. While the 

 material is still hot a drop of solder is placed upon the 

 opening in the top of the can. This thoroughly seals it 

 and the work is done. It is customary to keep the cans 

 in the factory for a while in order to test the efficacy 

 of the work. Any cans which later are found to be 

 swollen, indicating the accumulation of gas on the inside, 

 are discarded as ruined. In the ordinary process it fre- 

 quently happens that an occasional can either fails of ster- 

 ilization or of complete sealing ; the result of which is a 

 subsequent ruin of the product. Canning factories some- 

 times suffer great loss from the spoiling of their products. 

 In all these cases the cause is probably the presence 

 of resisting spores, and the remedy is the application of 

 greater heat. A knowledge of this fact has enabled can- 

 ning establishments in recent years to avoid in great 

 measure their previous losses. 



In certain kinds of canned food it has been customary to add 

 some mild antiseptic to aid in the subsequent preserva- 

 tion. The material most commonly used for this purpose 

 is borax, which is frequently found in cans of meat. Its 

 purpose is to check the development of any bacteria that 

 may be left in the meat after the process of canning. 



