TEMPEEATUBE CHANGES, ETC., DUEING CANNING OPEEATIONS. 25 



here again is emphasized the fact that the cooling curves are not the 

 exact reverse of the heating curves, for the final portion of the cool- 

 ing curve is flatter than the corresponding portion of the heating- 

 curve. No curves for cooling in air are shown here, but tests show 

 that it is very much slower than cooling in water. 



, PEAS. 



PRESSURE STUDIES. 



Peas used for the pressure tests were shelled, blanched in boiling 

 water for four minutes, drained, and then weighed into the test cans. 





































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Fig. 13. — Experimental time-temperature curves- for string beans in No. 3 tin cans start- 

 ing at different uniform temperatures and processed at 100°, 116°, and 121° C. Curve 

 is also shown for cooling in water at 20° C. Curve for can starting: A, At 26° C 

 and processed at 100° C ; a, at 20° C. and processed at 116° C. ; a', at 25° C. and 

 processed at 121° C. ; C, at 80° C. and processed at 100° C. ; c, at 80° C. and processed 

 at 116° C. ; c', at 80° C. and processed at 121° C. X, Cooling curve for can starting 

 at 116° C. and cooled in water at 20° C. 



For the No. 2 can 400 grams of peas and 170 c. c. of liquor were used. 

 The cans were sealed at the initial uniform temperatures of 20°, 70°, 

 and 80° C, respectively, and processed for one hour at 100°, 116°, 

 and 121° C. Figure 14 shows the time-pressure curves for these cans, 

 together with one curve for unblanched peas sealed at 19° and 

 processed at 116° C. 



As in the case of string beans, cans processed at 100° C. approached 

 an equilibrium of pressure in a length of time corresponding closely 

 to that required to reach a temperature equilibrium, that is about 15 

 minutes. At the higher processing temperatures the continued rise 

 in pressure is again noted, though in the case of the cans sealed at 



70344°— 22 4 



