44 



BULLETIN 1022, U. S. DEPARTMENT OF AGRICULTURE. 



ture of 70° C. ; processed at 116° C. for 30, 45, 60, TO, and 90 minutes, 

 respectively, and then cooled in air. 



The salient differences between these curves and those for No. 2 

 cans lie in the fact that the heat at the center of the No. 3 can con- 

















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120 130 140 ISO 



Fig. 30. — Experimental time-temperature curves for sweet potatoes in the form of pie 

 stock in No. 3 tin cans, starting at a uniform temperature of 70° C, processed for 

 different time periods at 116° C, and cooled in air at ordinary room temperature. 

 The arrows indicate when the cans, were removed from the retort. Curve for can 

 processed : A, For 30 minutes ; B, for 45 minutes ; G, for 60 minutes ; D, for 70 

 minutes ; E, for 90 minutes. 



tinues to rise for a longer time than in the No. 2 can, but the maxi- 

 mum temperatures attained are lower and the time the temperature 

 remains above 100° C. in the various tests is materially less. This is 

 due, of course, to the very slow rate of temperature changes in the 

 sweet potato. The difference in time during which they remain 

 above 80° C. is small, being slightly longer in the case of the No. 3 can. 



12* 

 310 

 300 



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Fig. 31. — Experimental time-temperature curves for sweet potatoes in the form of pie 

 stock in No. 3 tin cans, starting at a uniform temperature of 70° C, processed 

 for different time periods at 116° C, and cooled in water at 16° to 20° C. The 

 arrows indicate when the cans were taken from the retort and placed jn water. 

 Curve for can processed : A, For 30 minutes and cooled at 19° C. ; B, for 45 minutes 

 and cooled at 20° C. ; C, for 60 minutes and cooled at 17° C. ; D, for 75 minutes and 

 cooled at 19° C. ; E, for 90 minutes and cooled at 16° C. ; F, for 120 minutes and 

 cooled at 18° C. 



Figure 31 shows the experimental curves for water cooling of No. 

 3 cans handled in the same way as the above. 



As in the case of the No. 2 cans handled similarly, the tempera- 

 ture continues to rise after the cans are placed in cold water, but 



