TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 43 
perature of 70° C., processed at 116° for 30, 45, 60, 75, and 90 
minutes, and then cooled in air at 26° C. 
In the can processed for 30 minutes the temperature continues to 
rise for 20 minutes. A gradual reduction in the time during which 
the succeeding curves continued to rise is noted, the can processed 
for 90 minutes continuing only 5 minutes. In 30 minutes of process- 
ing the can did not reach 100° C. When air cooled the can processed 
for 45 minutes remained above 100° C. for 30 minutes; when proc- 
essed for 60 minutes it remained above that point for a little over 50 
minutes; when processed for 75 minutes, for about 70 minutes; and 
when processed for 90 minutes it remained above 100° C. for nearly 
90 minutes. The sig- 
nificance of Hee fig- Fh abate het tem 
“Figwe 29 shows PN 
DS O 
| ALN ARRAN 
0 
curves obtained under 
like conditions, except 
that the cooling was 
done in water at 17°C. 
It will be noted 
that with sweet pota- —} 
toes, even in wate 
? s Fie. 29.—Experimental time-temperature curves for sweet 
cooling, the tempera- potatoes in the form of pie stock in No. 2 tin cans, 
=e - tarting at a uniform temperature of 70° C., processed 
nti Yl E 
ture srt tinues to Se for different time periods at 116° C., and cooled in 
for a little while, but = water at about 17° C. The arrows indicate when the 
the time is much re- cans were taken from the retort and placed in water. 
Curve for can processed: A, For 30 minutes; B, for 45 
duced over what was minutes; C, for 60 minutes; D, for 75 minutes. 
obtained with air 
cooling. Within the range of these experiments the rise continued 
only from 5 minutes in the case of the can processed for 75 minutes 
to 8 minutes in the can processed for 30 minutes. 
As in the preceding figure, the temperature in the can processed 
for 30 minutes did not reach 100° C, at all; that processed for 45 
minutes remained above 100° C. for about 12 minutes; that processed 
for 60 minutes for about 28 minutes; and that processed for 110 min- 
utes for about 45 minutes. 
Comparing these figures with the figures for air cooling, we find 
that the time during ich cooking continues after 100° C. is reached 
is reduced by 18 minutes in the can processed for 45 minutes and by 
25 minutes in the can processed for 110 minutes. 
How one is able to control the cooking and thus prevent in a 
measure the caramelization of the material by water cooling of the 
cans is clearly illustrated. 
Figure 30 shows the experimental time-temperature relations for 
No. 3 cans of sweet potatoes starting at the initial uniform tempera- 
TEMPERATURE IN DEGREES CENTIGRADE 
0 
TIME IN MINUTES 
