TEMPERATURE-TIME RELATIONS IN CANNED FOODS 

 DURING STERILIZATION. 



GEORGE E. THOMPSON. 



Bacteriologists have found that the death rate of the bacteria 

 which cause spoilage in canned goods depends upon the tempera- 

 ture to which the bacteria are subjected. In order, therefore, 

 to establish the bacteriology of canning on a firm scientific basis 

 it is necessary to know the time at which certain critical tem- 

 peratures are attained by the foods which are subjected to the 

 sterilization process. This paper shows the result of an attempt 

 to work out by a combination of mathematical theory and experi- 

 ment the temperature-time cur^-es for certain foods in containers 

 of any size and for any practical temperature range. 



Apparently very little experimental w'ork has been done along 

 this line, and no attempt has been made, to the author's knowl- 

 edge, to apply well known mathematical theory. J. Kochs and 

 K, Weinhausen^ have measured with maximum thermometers the 

 temperatures attained in given times under certain practical con- 

 ditions, in cabbage, carrots, asparagus, apple musk and green 

 peas. A. W. Bitting and K. G. Bitting^ have published tem- 

 perature-time curves for pumpkin, sweet potatoes, tomatoes, 

 peaches, etc., while being heated in a water bath. Aside from 

 the reports of these men very little seems to have been published. 



MATHEMATICAL THEORY. 



In developing the mathematical thoory it will be assumed that 

 heat penetration is entirely due to conduction. This is obviously 

 not true except in very pasty substances, such as pumpkin, 

 mashed sweet potatoes, etc., but it is thought that in such cases 

 as com and peas where the convection currents must be mostly 

 very local in character the theory will still appl}' approximately 

 enough for practical purposes, the convection being in effect 

 equal to an increase of conduction. Also since the center of the 

 can is last to become heated and last to cool off, it is the most 

 important point to be considered and attention will be confined 

 entirely to it. 



In order to make the mathematical theory apply without too 

 much complexity, it is necessary to assume rather ideal condi- 

 tions, namely, that the contents of the can are of uniform tem- 

 perature throughout before immersion in the sterilizing bath, 



