TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 45 



the length of time is increased. In water cooling, even when proc- 

 essed for 60 minutes, the temperature never reaches 100° C. In ad- 

 dition to the facts brought out in the discussion on water-cooled No. 

 2 cans, the form of 

 the cooling curves 

 for No. 3 cans proc- 

 essed for the longer 

 periods is of inter- 

 est as illustrating 

 again the effect of 

 condensation of 

 steam within the 

 head space and the 

 consequent rapid 

 fall of temperature, 

 which has been 

 earlier considered. 

 These, with the 

 preceding curves, 

 are of great practi- 

 cal value in deter- 

 mining the length of the processing period of sweet potatoes. 

 Figure 32 shows the experimental curves for sweet potatoes in No. 

 2 cans, starting at the different initial temperatures, processed for 



Fig. 32. — Experimental time- temperature curves for sweet 

 potatoes in the form of pie stock in No. 2 tin cans, 

 starting at different uniform temperatures, processed for 

 45 minutes at 116° C, and cooled in air at ordinary room 

 temperature. Curve for can starting : A, At 20° C. ; 

 B, at 37° C. ; O, at 50° C. ; D, at 601° C. ; E, at 70° C. ; 

 F, at 80° C. 















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Fig. 33. — Experimental time-temperature curves for sweet potatoes in the form of pie 

 stock in No. 3 tin cans, starting at different uniform temperatures, processed for 

 1 hour at 116° C, and cooled in air at ordinary room temperature. Curve for can 

 starting : A, At 24|° C. ; B, at 381° C. ; G, at 51£° C. ; D, at 60° C. ; E, at 701° C. ; 

 F, at 80° C. 



45 minutes at 116° C, and cooled in air. Figure 33 shows the same 

 for the No. 3 can, except that the processing period is 60 minutes. 



These curves show the effect which different initial temperatures 

 have upon the maximum temperatures attained during a single 

 definite processing period, and they furnish a definite picture of the 



