TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. © ot 
cooled in water the maximum temperatures are usually reached at 
the time wher the cans are placed in the water. When cooling 
immediately in water is practiced one is able to control rather 
definitely the amount of cooking the corn will receive unless it is 
of very heavy consistency, when curves such as those shown in figure 
21 may be of very much value. 
The curves show that when the can is started at 80° C. and processed 
for 30 minutes at 116° the center of the can of corn never reaches 
100° C. when cooled 
in water. When proc- 
essed for 45 minutes it 
remains above 100° C. 
about 13 minutes, about 
30 minutes when proc- 
essed for 60 minutes, 
about 42 minutes when 
processed for 70 min- 
utes, and about 60 min- 
° a0 30 60 
utes when processed 90 Tea 
minutes. It remained Fic. 24.—Experimental time-temperature curves for 
“Maine style’’ corn in No. 2 tin cans, starting at a 
as ° 
above 110 C. for about uniform temperature of 80° C., processed for different 
15 minutes when proc- time periods at 121° C., and cooled in water at 23° 
ee i Z to 26° C. Proportion of corn to liquor, 4:1. The 
essec or 70 minutes, arrows indicate the time when cans were removed 
and for approximately from the retort and placed in water. Curve for can 
: processed: A, For 30 minutes; B, for 45 minutes; C, 
35 minutes when proc- 
for 60 minutes; D, for 90 minutes. 
essed for 90 minutes. 
Differences in initial temperatures and in the consistency of the 
corn, of course, would vary these figures. 
Figure 24 shows similar curves for corn handled in the same way 
as in the above tests, except that the retort temperature of 121° C. 
was employed. 
In the discussion of results obtained with string beans and peas the 
relationship of the time-temperature and the time-pressure curves 
was pointed out. In comparing the time-pressure and time-tempera- 
ture curves in sweet corn it is seen that the pressure rises very rapidly 
during the first minute or two of the processing period, owing to the 
heating of the head space. On the other hand, the temperature at 
the center of the can is still little changed, and the heat certainly has 
penetrated only slightly into the material. After several minutes, 
however, the pressure rises more gradually, corresponding closely to 
the rate at which the heat penetrates into the material. It does not 
correspond exactly to this, however, for there is a continuous rise of 
pressure so long as the processing is continued, this being more pro- 
nounced with the higher processing temperatures. 
TEMPERATURE IN DEGREES CENTIGRADE 
