TEMPERATURE CHANGES IN CANNING FRUITS AND VEGETABLES. 31 



Figure 31 shows the record of cooling for a No. 2 tin can in 

 air and in water. The cooling in air is considerably slower than that 

 of string beans, but the 

 differences are not so 

 great as might be ex- 

 pected from the differ- 

 ences in the rise in tem- 

 perature. The cooling in 

 water, although very 

 much faster than the cool- 

 ing in air, is still very 

 slow in comparison to the 

 cooling of string beans in 

 water. It requires about 

 1 hour and 20 minutes for 

 the corn to fall to 30° C. 

 in these tests, whereas 

 string beans required only 

 10 to 15 minutes. These 

 differences in the rate of 

 cooling in air and in 

 water. It required about 

 tremely important when it 

 is remembered that high 



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Fig. 33. — Time-teinperature relations for sweet corn 

 (Maine style) when processed in pint glass jars 

 at 100°, 109°, 116°, and 121° C. These curves 

 were plotted from temperature readings made at 

 intervals of 5 minutes. Rise in temperature when 

 processed : A, At 100° C. (the proportion of corn 

 to liquor in this case, unfortunately, was less than 

 in those processed at the higher temperatures) ; 

 B, at 109° C. ; C, at 116° C. ; D, at 121° C. 



temperatures seriously affect the appearance and flavor of the corn. 

 Attention is again called to the fact that when the steam is cut 



off at the end of the 

 processing* period the 

 temperature of the 

 jars falls from any 

 temperature above 

 100° to 100° C. as 

 rapidly as the tem- 

 perature in the re- 

 tort. This is impor- 

 tant, especially in 

 substances like corn, 

 as sterilizing tem- 

 peratures are main- 

 tained for much 

 shorter periods than 

 in tightly sealed 

 cans. 



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Fig. 34. — Time-temperature relations for sweet corn 

 (Maine style) when processed in quart glass jars at 

 100% 109°, 116°, and 121° C. These curves were 

 plotted from temperature readings made at intervals 

 of 5 minutes. Rise in temperature when processed : 

 A, At 100° C. (the proportion of corn to liquor in this 

 case, unfortunately, was less than in those processed 

 at the higher temperatures) ; B, at 109° C. ; C, at 

 116° C. ; D, at 121° C. 



VARIETAL DIFFERENCES. 



Other tests were 

 made to determine 



