18 



BULLETIN 956, U. S. DEPARTMENT OF AGRICULTURE. 



the purpose of determining to what extent these factors are of im- 

 portance in actual canning practice. No attempt to follow exactly 

 the procedure of any specific canning method was made, the object 

 being to get at the underlying principles and fundamental factors 

 of the time-temperature relations rather than to check up on pre- 



vailing methods. 



STRING BEANS. 



In the tests with string beans the Green Pod Stringless variety 

 was used. The beans were gathered from the field, brought into the 

 laboratory, washed, broken into pieces 1 to 1J inches long, and then 



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SO 60 70" 



Fig. 11. — Tinie-teinperature relations for string beans in 2 per cent brine when processed 

 in No. 2 tin cans at 100°, 109°, 116°, and 121° C. and also Avhen cooled in air and in 

 water. The curves representing the rise in temperature during processing and the fall 

 in temperature during cooling in water were plotted from readings made at intervals 

 of 1 minute and 1 minute ; those representing cooling in air, from readings at in- 

 tervals of 5 to 10 minutes. Rise in temperature when processed : A, At 100° C, ; 

 B, at 109° C. ; C, at 116° C. ; D, at 121° C. Fall in temperature when cooled : a', From 

 100° in water at 17° C. ; V , from 109° in water at 17° C. ; &, from 116° in water at 

 161° C. ; cl', from 121° in water at 16J° C. ; a, from 100° in air at 16° to 20° C. ; 

 ~b, from 109° in air at 19° to 22° C. ; c, from 116° in air at 18° to 22° C. ; d, from 

 121° in air at 19° to 22° C. 



blanched for five minutes in boiling water. They were then al- 

 lowed to cool to room temperature and placed in the cans. Two 

 per cent brine was added to fill the interspaces. They were then 

 processed at 100°, 109°, 116°, and 121° C. in No. 2 and No. 3 tin 

 cans and in pint and quart glass jars. Figures 11 to 14 show the 

 rise in temperature at the center of the various containers at the 

 different processing temperatures. 



It is observed that the rise of temperature is almost as rapid as that 

 of distilled water alone. In 12 to 13 minutes the temperature at the 

 center of the No. 2 tin can approaches or attains that of the retort 

 or bath, and in 15 to 16 minutes the temperature of the No. 3 can 



