TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 19 
The effect of initial temperature is easily seen from the curves. 
The temperature of the retort is reached six or seven minutes sooner 
when the initial temperature is 80° C. than when it is 20° C. It is 
apparent, therefore, that the initial temperature is of more signifi- 
cance when canning in glass than when canning in tin in those sub- 
stances where there is free liquid filling the interspaces of the 
product. 
Another matter of much importance is the study of the changes 
in temperature necessary to secure the proper exhaust. When a No. 
2 can of water having an initial temperature of 20° C. is exhausted 
for 1 minute at 100° C. the temperature reaches to about 60° C. A 
No. 3 can reaches about 50° C. The rate of change of temperature 
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TEMPERATURE IN DEGREES CENTIGRADE 
TIME IN MINUTES 
Fic. 7.—Experimental time-temperature curves for quart glass jars of distilled water, 
starting at different temperatures and processed at 100° C. Curve for jar starting: 
Besar ie eee eat te40sC. Oy at, 60% C.: D, at 80°"C.; FH, ak, 90° C. 
when exhausted at 100° is shown in figure 6, curve A. The applica- 
tion of these facts to the exhausting of various food substances will 
be considered and illustrated later. 
EXPERIMENTS WITH SPECIFIC FOOD MATERIALS. 
STRING BEANS. 
PRESSURE STUDIES. 
_ The tests upon string beans were carried out as follows: The beans 
were gathered fresh from the field, washed, broken into pieces 1 to 1} 
inches in length, and then blanched in boiling water for four minutes. 
For each one of the tests with the No. 2 can 350 grams of beans were 
used and 220 c. ec. of liquor, which gave approximately normal head 
space. In the case of the No. 3 can, 600 grams of beans and 360 ¢. ¢. 
of liquor were used. 
