TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 27 
In concussion tests upon cans in lots sealed at the various tem- 
peratures the results were somewhat variable, but differences in the 
resistance of No. 2 cans to denting did not seem to be very marked 
with sealing temperatures up to 70° or 80° C. Above 80° the 
susceptibility to denting became more and more marked and be- 
tween 95° and 100° C. the cans usually collapsed spontaneously. 
The No. 3 cans were more susceptible to denting than the No. 2 
size and their susceptibility became more and more marked above 
75° C. With sealing temperatures between 90° and 95° C. the can 
usually collapsed spontaneously or with very slight pressure. 
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Fig. 15.—Experimental time-temperature curves for peas in No. 2 tin cans, starting at 
different uniform temperatures and processed at 100°, 116°, and 121° C. Curves are 
also given for cooling from different temperatures in water at 24° C. Curve for can 
starting: A, At 26° C. and processed at 100° C.; a, at 20° C. and processed at 116° 
abe rand processed at 121° "Gs "Cs" at. 80° C. and processed at 100° C.; G&G 
at 80° C. and processed at 116° C.; c’, at 80° C. and processed at 121° C.; D, at 
100° C. and processed at 121° €. Cooling curve for can starting: X, At 100° C. and 
cooled in water at 24° C.; Y, at 116° C. and cooled in water at 24° C.; Z, at 121° C. 
and cooled in water at 24° C, 
HEAT PENETRATION. 
The results of experiments on the rate of change of temfperature 
in No. 2 cans of peas having different temperatures are shown in 
figure 15. These show that when cans are sealed at the various 
initial temperatures and processed at the same retort temperatures 
the heat penetration curves closely approach each other in the first 
four or five minutes of the process, and the difference in the length 
of time required to reach’ retort temperature amounts to only two 
or three minutes. The curves do not differ markedly from those for 
distilled water. The rate of temperature change in glass, although 
not shown here, is considerably slower than in the tin and agrees 
closely with that shown for string beans. 
