TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 45 
the length of time is increased. In water cooling, even when proc- 
essed for 60 minutes, the temperature never reaches 100° C. In ad- 
dition to the facts brought out in the discussion on water-cooled No. 
2 cans, the form of 
the cooling curves 
for No. 3 cans proc- 
essed for the longer 
periods is of inter- 
est as illustrating 
again the effect of 
condensation of 
steam within the 
head space and the 
consequent rapid 
fall of temperature, a a a 
which has been Fig. 32.—Experimental time-temperature curves for sweet 
earlier considered. potatoes in the form of pie stock in No. 2 tin cans, 
Th ° + a starting at different uniform temperatures, processed for 
ese, wit the 45 minutes at 116° C., and cooled in air at ordinary room 
preceding Curves, . temperature. Curve for can starting: A, At 20° C.; 
f t ti Beat 37°) C30; at 50° \C.\ D5 at 603° C+ HB, at 70° C.; 
are of great practi- F,-at 80° C. 
cal value in deter- 
mining the length of the processing period of sweet potatoes. 
Figure 32 shows the experimental curves for sweet potatoes in No. 
2 cans, starting at the different initial temperatures, processed for 
UO; 
esr 
Pee 
Boo7 2 Seen 
2) deacee 
64 (ane an 
TEMPERATURE IN OLGREES CENTIGRAOE 
\\ 
NN 
AW 
N 
NC 
X 
my 
See cal ate 
BSA o 
~ 
JE SUS ES 
TEMPERATURE IN DEGREES CENTIGRADE 
1 
TIME IN MINUTES 
I'ic. 33.—Experimental time-temperature curves for sweet potatoes in the form of pie 
stock in No. 8 tin cans, starting at different uniform temperatures, processed for 
1 hour at 116° C., and cooled in air at ordinary room temperature. Curve for can 
Rete SC at, ote. Cs) Bat 382° C.3 0, at. 514° C.; D, at 60°. C.: ZH, at 704° C.: 
F, at 80° C. ° 
45 minutes at 116° C., and cooled in air. Figure 33 shows the same 
for the No. 3 can, except that the processing period is 60 minutes. 
These curves show the effect which different initial temperatures 
have upon the maximum temperatures attained during a single 
definite processing period, and they furnish a definite picture of the 
