38 



BULLETIN 956, U. S. DEPARTMENT OF AGRICULTURE. 



been entirely different. If the initial temperature of the material 

 when put into the can had been higher, the maximum temperature 

 attained would also have been higher. 



Fig, 43. — Time-temperature relations for sweet potatoes when processed in No. 3 tin cans 

 at 116° C. for 50, 60, TO, 80, 90, and 100 minutes and then removed to the air at 

 20° to 25° C. These curves were plotted from readings made at intervals of 5 minutes. 

 Temperature curve when processed and placed in air : A, For 50 minutes ; B, for 60 

 minutes ; C, for 70 minutes ; D, for SO minutes ; E, for 90 minutes ; F, for 100 minutes. 



It is obvious that the initial temperature in the can should be 

 uniform, in all cans of the pack where the same processing is to be 

 given, and the initial temperature should also be as high as pos- 



20 ao '?0 SO SO 



/SO /<?0 /SO /eo /70 /SO /SO 200 



Fig. 44. — Time-temperature relations for sweet potatoes when processed in Xo. 3 tin cans 

 for 1 hour at 100°, 109°. 116°, and 121° C. and then removed to the air at 20° to 25° C. 

 These cuives were plotted from readings made at intervals of 5 minutes. Temperature 

 curves when processed for one hour : A, At 100° C. ; B, at 109° C. ; C, at 116° C. ; 

 D, at 121° C. 



sible, in order that the processing period may be shortened. Start- 

 ing at a temperature higher than that of the room is to be recom- 

 mended. 



PROCESSING EOR ONE HOUR AT DIFFERENT TEMPERATURES. 



Figure 44 shows curves for Xo. 3 tin cans of sweet potatoes proc- 



C. for 1 hour in the retort, or 



essed at 100°, 109°, 116°, and 121 ( 



