TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 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. 
IM DEGREES CENTIGRADE 
TEMPERATURE 
TIME IN MINUTES 
Fic. 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 26° C. and processed at 116° C.; a’, at 25° C,. and 
processed at 121° C.; CO, 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 ¢. ¢. 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 liigher processing temperatures the continued rise 
in pressure is again noted, though in the case of the cans sealed at 
70344°—22- 4 
