34 BULLETIN 1022, U. S. DEPARTMENT OF AGRICULTURE. 
These figures seem to indicate that sealing at initial temperatures 
as high as 85° C., or even higher, may be practiced without great | 
danger of serious Achtung or collapsing of No. 2 tin cans. q 
Various influences tend to affect the results in individual cans— 
. the weight of the tin plate from which they are made, the perfection 
in form, etc. The data shown in Table 10 represent an average for. 
one lot of cans and are given for what they are worth. | 
HEAT PENETRATION. 
The time-temperature relation for a No. 2 can of corn started at 
various initial temperatures, processed for various lengths of time. 
under different retort conditions, and cooled in air and in water are 
given below. 
ro. Bee = papers’ pe] 
> > Se 
Sa Ss Ss =" ae 
PB 
TEMPERATURE IN'DEGREES CENTIGRADE 
r) 10 20 - 30 - 40 Te 80 
30 1060 110 120 130 0 150 160 170 180 190 200 
TIME IN MINUTES = 
Fig. 21.—Experimental time-temperature curves for ‘‘ Maine style”’ corn in No. 2 tin 
cans, starting at different uniform temperatures and processed at 116° C. Proportion 
of corn to liquor, 4:1. Curves are also given for cooling in air at 26° C. and for 
cooling in water at 20° C., one curve of which is for corn of heavier consistency. 
Curves for can’ starting =-A5° At 26° €.3-B; at 404° C3 C, at-=50° -€.; D> at Gi°'C.; 
BH, at 70° C.;.F, at 80° C..3.G, at 9024°--C.; HA, at-100°_ €.; X, at 116° C: and; cooled 4a 
air at 26° C.; Y, at 116° C. and cooled in water at 20° C.; Z, at 116° C. and cooled 
in water at 20° othe SOnsisten cy of the corn being Teas than that represented 
in curve Y. 
Figure 21 gives the experimental heat-penetration curves for No. 
2 cans of corn starting at various temperatures and processed at 
GAC: 
These show how differences in initial temperatures: modify the 
form of the time-temperature curve. Theoretically, the temperature 
at the center of the can should reach the temperature of the retort in 
the same time for any_initial temperature, but in these tests the cans 
starting at the higher initial temperature actually reached the tem- 
perature of the retort in a slightly shorter time. This would seem to 
be due to some convection occurring in corn of this consistency. | 
Thompson (9) has given a formula by means of which from a 
single experimentally d>termined heat-penetration curve one may 
