TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 388 
(8) Great pressures are developed when the corn is not precooked, owing 
to the swelling of the starch and to the included air. 
(4) The continued rise in pressure due to the liberation of gases, while 
shown, is partially masked, for the reason that the temperature at the center 
ef the can did not reach the retort temperature during the processing period. 
(5) The rate of rise in pressure during processing is greater at the higher 
processing temperatures. 
(6) The maximum pressures are all somewhat below the theoretical and 
somewhat (except in the case of those not precooked) above that for water 
alone, in which the pressures are considerably below the theoretical. 
VACUUM STUDIES. 
The vacuum readings on cans used in the tests sealed at 70° and 80° 
C. are shown in Table 9. 
TABLE 9.—Vacuum tests with corn in No. 2 tin cans. 
Temperature (°C.). Barometer readings. 
Vacuum 
prec of mer- 
Sealin Proc- After |(minutes.) At After cury) 
E- essing. | cooling. sealing. | cooling. y 
100 223 120 30. 05 29. 99 12 
DSR SPs nh tn a a ereiniacie tia Sialois SelelS e/a wes pie 116 25 110 29. 99 29. 86 9% 
121 174 121 30. 08 29. 92 QZ 
80 100 29 140 29.56 29.62 153 
pf SSIS A eT he Ache aa th a 116 243 120 29. 99 30. 01 134 
- 121 244 120 30. 01 30. 05 13 
As in tests upon other materials the higher the processing tem- 
perature the lower the vacuum, owing to the liberation of gases dur- 
ing processing. Repeated experiments have shown that for the same 
reason the longer the processing period the smaller the vacuum. All 
results are below the theoretical figures. 
Vacuum readings with corn in No. 2 cans sealed in lots at various 
temperatures and processed intermittently for 14 hours at 100° C. 
gave the figures shown in Table 10. . 
Concussion tests with corn prepared as in these vacuum tests showed 
that the susceptibility to denting gradually increased with the rise of 
sealing temperature. The figures obtained are also shown in Table 10. 
TABLE 10.—Vacuum readings and concussion tests with corn in No. 2 tin cans. 
| Vacuum Fall of 
Sealing temperature (°C.). (inches of | weighted 
mercury). | can (cm.). 
