VITAMIN C 211 



was dried by a spray process in which the milk is first evaporated in a 

 continuous vacuum evaporator, pasteurized in a closed glass-lined tank 

 at 145° F. for 30 minutes and then dried instantaneously by being 

 forced into a heated chamber under very high pressure. The freshly 

 prepared milk powder showed no destruction of vitamin C. This was 

 attributed to the rapidity of the drying process and the absence of 

 oxygen during the pasteurization. No claims were made for the vitamin 

 C content of other milk powders. 



Human milk and goats' milk undoubtedly vary in their vitamin C 

 content in the same manner as cows' milk and, according to the limited 

 amount of evidence available, are not likely to be much richer in vitamin 

 C than cows' milk produced under the best feeding conditions. It is 

 probably best to recommend that all infants be given some such anti- 

 scorbutic food as orange juice or tomato juice. If this is done the 

 possible variations in vitamin C content among the different forms of 

 milk are of little concern. 



Chemical Behavior of Vitamin C 



The pioneer studies of Hoist and Frolich demonstrated the de- 

 struction, wholly or in part, of antiscorbutic properties in foods when 

 heated under the conditions of their experiments ; and in other investi- 

 gations which followed, evidence of a more or less quantitative nature 

 was obtained regarding the instability of vitamin C. Thus La Mer, 

 Campbell and Sherman (1921, 1922) in an investigation of the effect 

 of temperature and of hydrogen-ion activity upon the rate of destruc- 

 tion of vitamin C, estabHshed time curves for destruction of the vitamin 

 at 60°, 80°, and 100° C. in an aqueous medium of the acidity of natural 

 tomato juice and some effects of other variables under stated condi- 

 tions. The results of the study may be briefly summarized as follows : 



Effect of Heating in Acid Solution. — In the case of tomato juice of 

 natural acidity, pH = 4.3, it was found that boihng for one hour de- 

 stroyed practically 50 per cent, and for four hours practically 68 per 

 cent of the antiscorbutic vitamin present. The time curve of the destruc- 

 tive process is, therefore, much flatter than that of a unimolecular reac- 

 tion or of a reaction proceeding according to the square root rule of 

 Schiitz. Similar flattening of the time curves of the destruction of 

 the vitamin were found also in experiments in which the tomato juice 

 was heated at temperatures lower than boiling, viz. at 60° C. and at 

 80° C. Comparisons of the data obtained at 60°, 80°, and 100° C. show 

 relatively low temperature coefficients : 



Oio (60°-80°) =1.23; Q,, (80°-100°) = 1.12. 



