TEMPEBATUEE CHANGES, ETC., DUBING CANNING OPEBATTONS. 43 















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perature of 70° C, processed at 116° for 30, 45, 60, 75, and 90 

 minutes, and then cooled in air at 26° C. 



In the can processed for 30 minutes the temperature continues to 

 rise for 20 minutes. A gradual reduction in the time during which 

 the succeeding curves continued to rise is noted, the can processed 

 for 90 minutes continuing only 5 minutes. In 30 minutes of process- 

 ing the can did not reach 100° C. When air cooled the can processed 

 for 45 minutes remained above 100° C. for 30 minutes; when proc- 

 essed for 60 minutes it remained above that point for a little over 50 

 minutes; when processed for 75 minutes, for about 70 minutes; and 

 when processed for 90 minutes it remained above 100° C. for nearly 

 90 minutes. The sig- 

 nificance of these fig- 

 ures is apparent. 



Figure 29 shows 

 curves obtained under 

 like conditions, except 

 that the cooling was 

 done in water at 17° C. 



It will be noted 

 that with sweet pota- 

 toes, even in water 

 cooling, the tempera- 

 ture continues to rise 

 for a little while, but 

 the time is much re- 

 duced over what was 

 obtained with air 



cooling. Within the range of these experiments the rise continued 

 only from 5 minutes in the case of the can processed for 75 minutes 

 to 8 minutes in the can processed for 30 minutes. 



As in the preceding figure, the temperature in the can processed 

 for 30 minutes did not reach 100° C. at all; that processed for 45 

 minutes remained above 100° C. for about 12 minutes; that processed 

 for 60 minutes for about 28 minutes ; and that processed for 110 min- 

 utes for about 45 minutes. 



Comparing these figures with the figures for air cooling, we find 

 that the time during which cooking continues after 100° C. is reached 

 is reduced by 18 minutes in the can processed for 45 minutes and by 

 25 minutes in the can processed for 110 minutes. 



How one is able to control the cooking and thus prevent in a 

 measure the caramelization of the material by water cooling of the 

 cans is clearly illustrated. 



Figure 30 shows the experimental time-temperature relations for 

 No. 3 cans of sweet potatoes starting at the initial uniform tempera- 



Fig. 29. — Experimental time-temperature curves for sweet 

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

 starting at a uniform temperature of 70° C.„ processed 

 for different time periods at 116° C, and cooled in 

 water at about 17° C. The arrows indicate when the 

 . cans were taken from the retort and placed in water. 

 Curve for can processed : A, For 30 minutes ; B, for 45 

 minutes ; C, for 60 minutes ; D, for 75 minutes^. 



