VITAMINS — MUNSELL 247 



In canning there is apparently no loss of vitamin Bi from process- 

 ing, the greatest loss taking place during blanching or other proce- 

 dures where there is a chance for solution. There are very few data 

 to support a statement concerning the effect of storage on vitamin 

 Bi in canned foods. Losses noted were determined after about 6 

 months' storage and ranged around 40 percent. 



Practical information on the inactivation of vitamin Bi in foods 

 during drying is almost entirely lacking. The vitamin seems to be 

 retained fairly well by foods dried at a temperature of 60° C. but at 

 higher temperatures destruction is probably considerable. 



VITAMIN O (AS(X)RBIC ACm) 



Properities. — Vitamin C in its pure form is a white crystalline 

 material with an acid taste and is readily soluble in water. It is 

 inactivated by oxidation and the rate of destruction increases 

 rapidly with increase in temperature. The degree of acidity of the 

 mixture also has a marked influence on the stability of vitamin C. In 

 an acid mixture like tomato juice it is destroyed only slowly, but in 

 less acid solutions the rate of destruction is much more rapid. 



Inactivation of vitamin C by oxidation proceeds in two steps. By 

 mild oxidative processes a substance called dehydroascorbic acid is 

 formed. This substance, which functions in the animal body as vita- 

 min C but does not respond to the usual chemical test, may be re- 

 duced to ascorbic acid. Under more drastic conditions of oxidation 

 the vitamin is completely inactivated and its activity may not be 

 restored. 



Food sources. — Vitamin C maj^ well be called the vitamin of fresh 

 foods. This does not mean fresh from the market, but fresh from 

 the plant or animal that produced the food. One authority has said, 

 "with the exception of ripe seeds, practically all fresh foods of either 

 plant or animal origin contain generous amounts of vitamin C." 



Fruits and vegetables are, on the whole, the richest sources of 

 vitamin C. There is a tendency, however, to limit the emphasis to 

 fruits and vegetables that can be eaten raw, and more especially to 

 the citrus fruits and tomatoes. Since these specific products are not 

 only outstandingly rich sources of the vitamin but also retain their 

 potency remarkably well during the various treatments to which 

 they may be subjected, they have come to be considered almost 

 essential in the diet. This tendency should probably not be encour- 

 aged to the extent of diverting attention from other fruits and vege- 

 tables that are equally important for vitamin C. In some localities 

 and at certain times of the year other fruits and vegetables, if 

 handled so as to conserve their vitamin-C value, might be more 

 economical than citrus fruits or tomatoes. 



