538 



MICROBIOLOGY OF FOODS 



in the presence of fifty thousand spores as in the presence of about 

 twenty spores. 



Size of Container. Assuming the same food product, it naturally 

 follows that a large can would require a longer time for processing than 

 a small one, the rapidity of heat penetration varying according to the 

 size of the can. 



Consistency of Contents of the Container. Consistency is expressed 

 in the way it is determined when a can is examined after it has been 

 packed, that is, in terms of drained solids. A can containing twenty- 

 seven ounces of drained solids will require a longer processing time than 

 the same size can containing only eighteen ounces of drained solids. Or, 

 to apply the principle in another way, a product such as peas or carrots 

 will require less time for heat penetration than corn or spinach in which 

 the food is packed more closely in the can. 



Initial Temperature. Foods filled into the cans hot can be success- 

 fully processed in a shorter time than if packed cold. This is especially 

 true in the case of such goods as corn in which the heat penetration is 

 slower than with some other products such as peas. 



00^ 



/0/5 ^0 25 30 35 



50 55 GO 65 



FIG. 154.- -Tomatoes in no. 3 cans Influence of speed of rotation on heat 



penetration. 



Agitation of the Container during Processing. This factor can best 

 be explained by Fig. 154 which shows the influence on heat penetration 

 of rotating a can of tomatoes while it is being processed. The can 

 represented by curve "B' : was processed in the ordinary steel retort 

 without rotating. The can in curve "A" was processed continuously 



