14 



BULLETIN 956, U. S. DEPARTMENT OF AGRICULTURE 



cans processed at temperatures above 100° and cooled in air the 

 sudden drop in temperature to 100° C. is not noted, the temperature 

 falling gradually, and still more slowly as it approaches that of the 

 room. These differences in cooling between the tin and glass con- 

 tainers are to be observed throughout the whole series of experi- 

 ments. 



One fact of importance shown by the curves is that the length of 

 time required for the center of any can to attain the temperature of 

 the bath or retort is approximately the same for all the tempera- 

 tures here used, except that in some tests the boiling-water bath 

 required a slightly longer time. 



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Fig. 7. — Time-temperature relations for distilled water when processed in quart glass 

 jars at 100°, 109°, 116°, and 121° C. and also when cooled in air. The curves repre- 

 senting the rise in temperature during processing were plotted from readings made 

 at intervals of 30 seconds ; the curve representing cooling in air, from readings at 

 intervals of 5 to 15 minutes. Rise in temperature when processed : A, At 100° C. ; 

 B, at 109° C. ; C, at 116° C. ; D, at 121° C. a, Fall from 100° C. when cooled in air 

 at 18° to 20° C. 



BRINE. 



. To determine whether the addition of salt would have any direct 

 influence upon the rate of change in temperature in the can, com- 

 parative tests were made, using distilled water, a 2 per cent brine, 

 and a saturated brine. In figure 8 curves for saturated brine and 

 distilled water show that the difference between distilled water and 

 a saturated brine is insignificant. From the results of these experi- 

 ments it is concluded that the proportion of salt commonly added to 

 canned materials has no direct effect upon the rate of change of 

 temperature at the center of the can. 



SUGAR SOLUTIONS. 



In order to get an idea of the possible effect that the addition of 

 sugar to canned materials has upon the rate of change of temperature 



