TEMPERATURE CHANGES IN CANNING FRUITS AND VEGETABLES. 3 



In the various discussions of their work the fact was also pointed 

 out that the quantity of liquor added to corn affects the rate at which 

 heat penetrates into it. 



Duckwall (9) in 1905 reported similar experiments with peas. He 

 also found that, regardless of the temperature of processing, the 

 temperature in the can reached that of the retort in the same length 

 of time. 



In the same year Belser (1), working upon the spoilage of canned 

 foods, also reported upon studies of the time-temperature relations in 

 the cans. He worked with peas, beans, mixed vegetables, carrots, 

 tomato puree, comfrey, spinach, sauerkraut, cherries, and apple pulp. 

 Maximum temperatures during the processing were obtained by the 

 use of maximum thermometers, and numerous tables of results were 

 given. These show, as might be expected, considerable variations in 

 the temperatures reached by the different foods when handled under 

 identical conditions. Belser pointed out the great importance of know- 

 ing the speed at which the heat penetrates to the center of the cans 

 and performed several experiments with peas and beans to de- 

 termine this. The method of preparation of material, the nature of 

 the containers, and the details of his work were such as to make 

 direct comparisons with American work impossible. 



Haselhoff and Bredemann (10) in their report of investigations 

 upon the decomposition of canned foods (1906) referred briefly to an 

 apparently unpublished work of Huber in which attention was called 

 to the fact that during the processing of certain food products the 

 temperature inside the containers often did not reach that of the 

 bath or retort in which they were processed. 



Kochs and Weinhausen (11) carried on experiments (1906-7) 

 with cabbage, carrots, asparagus, apple sauce, and peas. The 

 methods employed correspond closely to those of Belser (1), and 

 their results are not comparable with the findings of American 

 workers. They pointed out that the rate of heat penetration is de- 

 pendent upon the firmness of the pack and the proportion of liquid 

 present. They worked also with glass and stoneware containers. 



Bitting (2), in 1912, described two methods for the determination 

 of the rate of heat penetration in cans of food. One method made 

 use of long-stemmed thermometers held with the bulb at the center 

 of the cans by means of a special device whereby direct reading of 

 the temperature was made possible. The second method made use 

 of thermocouples. For the higher temperature chlorid baths were 

 used. Bitting pointed out that in substances having plenty of free 

 liquid the heat passed in much more rapidly than in substances of 

 heavy consistency and with less liquid. The advantages of agita- 

 tion in shortening the cooking period were emphasized. No ex- 

 perimental data were given, however. 



