200 THE VITAMINS 



vegetables at temperatures above boiling-point for as short a time as 

 possible to insure sterility." 



Eddy and associates (1923) reported a 95 per cent destruction of 

 vitamin C in cabbage when cooked until palatable either by boiling in 

 an open kettle or by cooking in a pressure cooker. Cabbage canned 

 by ordinary commercial methods was found by Eddy and Kohman 

 (1924) to have lost only about one-fourth of its vitamin C potency. 

 The method followed consisting of packing the cabbage in No. 2 cans, 

 filling the cans with hot water, passing live steam through for 2 or 3 

 minutes, and then sealing and processing them. The times and tem- 

 peratures of processing included 30 and 60 minutes at 100° C, 15, 30, 

 and 45 minutes at 115° C. and 30 minutes at 126° C. These variations 

 apparently had no important effect upon the antiscorbutic properties 

 of the cabbage, indicating that the slight destruction of vitamin C took 

 place mainly during the initial treatment with steam. In this investiga- 

 tion a slight increase in the potency of raw cabbage on storage was 

 noted. 



In a similar study of spinach, Eddy, Kohman, and Carlsson (1925) 

 found that, on a strictly vitamin-C-free basal ration, guinea pigs were 

 protected by 1 gram daily of the fresh raw material while on a basal 

 ration later found to be not entirely free from vitamin C a dosage 

 of 0.25 gram of the raw material proved sufficient. With the second 

 basal ration it required the equivalent of 10 grams of home-cooked 

 spinach or of 4 grams of commercially canned spinach to afford the 

 same protection. For the home-cooked materials the standard house- 

 hold method was followed of cooking the freshly washed material for 

 15 minutes without additional water. The canned spinach was pre- 

 pared according to the commercial methods by blanching in hot water 

 for two minutes and processing for 70 minutes at 115° C, using No. 

 2^ cans, and also by blanching 5 minutes in water and 1 minute in 

 steam and processing for 70 and 120 minutes, respectively. There was 

 some evidence that the 5 minute blanch was more destructive than 

 the two or one minute blanch. Later studies at the South Dakota Agri- 

 cultural Experiment Station (1929) have indicated a greater destruc- 

 tion of vitamin C in spinach in blanching than in processing. 



In discussing their results Eddy and his associates state : 



"The results obtained by the writers in their studies of cabbage, apples, and 

 spinach all tend to confirm the view that oxidation factor is more important than 

 the heat factor. There is no question but that acidity or alkalinity is a factor 

 and that heat accelerates destruction, but when these other factors are constant 

 wide variation in the destruction may be obtained by controlling the oxygen factor 

 alone. It is possible that this factor is not eliminated by mere exclusion of air ; 



