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18 BULLETIN 1022, U. §. DEPARTMENT OF AGRICULTURE, — 
tests, using No. 3 cans sealed at different Beciae es and processed 
at 116° C, , 
The temperature of the retort is reached calls one to one ane one- 
half minutes sooner when the initial temperature is 80° than when it 
is 20° C. A comparison of these curves With similar ones for different 
food substances shown later will be found to be of interest. Cooling 
curves are also shown for the No. 3 can cooled from 116° in water 
at constant temperature to 60° and 20° C., respectively. While, as 
in the heating, the temperature changes within the can take place very 
rapidly, the ee and the = curves are not the exact reverse 
TEMPERATURE IN DEGREES CENTIGRADE 
Time IN MINUTES ~ =~ 
Fic. 6.--Experimental time-temperature curves for distilled water in No. 3 tin cans, 
starting at different uniform temperatures and processed at 116° C. The heating 
curve is shown for a can starting at 20° C. and processed at 100° C.; and curves 
showing the rate of cooling. in waiter at different temperatures. Curve for can start- 
ing: A, At 20° C. and processed at 100° C.; B, at 20° C. and processed at 116° C.; 
C, at 40° C. and processed at 116° C.; D, at 60° C. and processed at 116° C.3; H, at 
80° C. and processed at 116° C.; F, at 100° C. and processed -at-116° C.; G, at 110° 
C. and processed at 116° C.; X, at 116° C. and cooled in water at 60° C.; Ys at-116° 
C. and cooled in water at 20° Cc 
of each other. This is due in part, of course, to the fact that the 
viscosity of water changes with changes in eee As the 
temperature in the can approaches the temperature of the cooling 
bath there is a flattening out of the curve, due in part to the increase 
in viscosity of the water, which is much more marked than in the 
corresponding portion of the heating curve, where the viscosity is 
continuously diminishing and the time required to effect the complete 
change is materially lengthened. 
ene 7 shows the rate of temperature change at the center of a 
quart glass jar with water sealed at Oe temperatures and pro- 
cessed at 100° C. | 
a 
