TEMPERATURE CHANGES IN CANNING FRUITS AND VEGETABLES. 47 



case to be between 1 and 1J hours, which is probably sufficient to 

 allow the germination of most spores. The temperature remained 

 below 30° for the remainder of the 24 hours. 



During the second processing the time-temperature relations were 

 practically the same as during the first. The rate of change of tem- 

 perature was very slightly slower, but this was insignificant. 



The result of the third processing was essentially the same as the 

 second. There was no change in the first heating, which affected 

 materially the rate of change of temperature in the second and third 

 processing. 



SWEET CORN. 



The variety of sweet corn used in these tests was Stowell's Ever- 

 green. Ears which were in prime condition for canning were selected 

 in the field. They were husked, the silks were removed with a coarse 

 brush, and they were then washed in water. The corn was prepared 

 " Maine style " and enough brine-sugar solution (2 per cent salt and 

 6 per cent sugar) was added to make the proportion 4.5 of corn to 



1 of liquor. It was then processed for exactly one hour on each of 

 three successive days. The time-temperature curves for No. 2 and 

 No. 3 tin cans and for pint and quart glass jars are shown in figure 53. 



The results shown here are very different from those for string 

 beans. The temperature, instead of rising rapidly, went up very 

 slowly. In no case did it reach 100° C. The temperature was rising 

 when the cans were removed from the bath and continued to rise 

 for a considerable time after being placed in the air. The pint glass 

 . jar went highest, the No. 2 tin can next, then the quart glass jar, 

 with the No. 3 tin can lowest. The order in which they heated up 

 was different from that of string beans. All the cans went above 

 80° O.j which is sufficient to destroy most vegetative forms of bac- 

 teria. The cooling was quite slow. The temperature fell to 60° C. 

 about as follows : No. 2 tin can, 2 hours and 5 minutes ; No. 3 tin can, 



2 hours and 20 minutes; pint glass jar, 1 hour and 25 minutes; and 

 quart glass jar, 1 hour and 50 minutes. The temperature of the con- 

 tainers remained between 30° and 40° C, as follows : No. 2 and No. 3 

 tin cans, 3 hours; the pint glass jars, 2 hours and 20 minutes; and the 

 quart glass jars, 2 hours and 45 minutes. For the remainder of the 

 time the temperature remained below 20° C, reaching 19° over night. 



The initial temperature in the second processing was lower than in 

 the first, and consequently the maximum temperature reached was 

 lower. The curves took nearly the same form the second day as the 

 first, showing that there had been but little alteration in the rate of 

 change of temperature at the center of the can. The results were 

 quite similar to those of the first processing. The results for the third 

 processing were essentially the same as for the second. 



