46 



BULLETIN &56, U. S. DEPARTMENT OF AGRICULTURE. 



cans remained at about 100° C. for a period varying between 40 and 

 60 minutes each, and the pint and quart ghiss jars for a period be- 

 tween 25 and 30 minutes. At the end of one hour they were taken 

 immediately from the bath and put in the air. The cooling was slow. 

 The temperature fell to 60° C, as follows : No. 2 tin can, 1 hour and 25 

 minutes; No. ,3 tin cans, 1 hour and 40 minutes; pint glass jars, 1 



90 eo 80 



/OO /20 /^<? /60 /eo 200 220 290 260 2SO 300 320 

 TIME IN MINUTES 





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a 

















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^ 



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I 



















F= 































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B 





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? 2C 



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6C 



1 &. 



/Oi 



? /2 



T// 



O /6 



o /& 

 ■\/ M/A 



O 2C 



/UTE 



O 2!i 

 S 



'O £^ 



?C> 3t 



~0 21 



JO 2S 



O '300 



SO ^<5 eo so /OO /2o /^K> /60 lao 200 220 a^fo zeo aao 300 aso 



TIME IN MINUTES 



Fig. 52. — Time-temperature relations for string beans in various containers when proc- 

 essed for 1 hour on each of three successive days (the intermittent process) at 100° C. 

 in the boiling-water bath : A, First day ; B, second day ; C, third day ; a. No. 2 tin cans ; 

 l). No. 3 tin cans ; c, pint glass jars ; d, quart glass jars ; x, temperature curve for water 

 bath ; y, temperature curve for room. The interval between the end of the curves in 

 A and the beginning of the curves in B was 18 hours and 40 minutes. The same period 

 of time elapsed between the end of the curves in B and the beginning of the curves 

 in G. 



hour; and the quart glass jars 1 hour and 20 minutes. The order of 

 their cooling was pint jars fastest, quart jars next, then the No. 2 

 tin cans, and No. 3 tin cans slowest. 



Since the optimum temperature for the germination of most bac- 

 terial spores is between 30° and 40° C, the length of time that the 

 can remains at this temperature is important. It was found in this 



