738 XI. VITAMINS E (tocopherols) 



unfavora])le, and oxidation of the fat was accelerated. Moreover, Krukov- 

 sky and Loosli^^ noted that supplementation of the diet of cows with 1 to 

 2 g. of mixed tocopherols per cow raised the tocopherol content of the milk- 

 fat and increased its resistance to oxidati^'e deterioration. The pre^'ention 

 of oxidized fla\'ors in milks was later sho\\ni to be correlated with the in- 

 creased tocopherol content produced by feeding the vitamin. ^^^ However, 

 no improvement occurred when tocopherol supplements were fed to cows 

 at the end of the winter season. It was concluded that tocopherol cannot 

 be used to maintain the tocopherol content of milk fat or to prevent the 

 oxidized flavor under all conditions. Moreover, Nielsen and co-workers^''' 

 in Denmark were unable to increase the keeping quality of butter made 

 from the milk of cows gi\'en 2 g. of DL-a-tocopheryl acetate dail}^, although 

 the tocopherol content of the butter was increased from 10 to 12 /zg/'g., in 

 the unsupplemented control group, to 23 to 26 )Ug-/g- iii the supplemented 

 group. However, the experimental details of the two conflicting reports 

 differ. It seems probable that, under certain conditions, the tocopherols 

 can reduce the oxidized fla\-or in milk, and increase its stability against 

 deterioration. 



b. The 171 vitro Action of Vitamin E as an Antioxidant. Olcott and 

 Mattill,^'''^ and Bradway and Mattill"*'^ first concentrated the natural 

 antioxidants in oils by the procediu'es useful for the preparation of \dtamin 

 E. It had previously been impossible to separate these antioxidants (or 

 inhibitols) from vitamin E. Since the isolation' of several forms of vitamin 

 E (the tocopherols) it has been fomid that a-tocopherol is most effective as 

 an antisterility agent, while /3- and 7-tocopherols excel as antioxidants.^^ 

 5-Tocopherol has been found to have the highest antioxidant activity of 

 any of the tocopherols.^ The addition of a-tocopherol or of mixed to- 

 copherols to fats or to fat-containing products is now widely used as an in 

 vitro method of preventing rancidity. A number of products such as 

 ascorbic, citric, and phosphoric acid may act as synergists, while \'itamin A, 

 carotene, cephalin, methionine, sulfhydryl groups, and crude sources of the 

 vitamin B complex also ser^•e in that capacity. For a more complete 

 exposition of the role of tocopherols as antioxidants, and of their relation- 

 ships to the synergists, the reader is referred to The Lipids, Vol. I, pp. 

 281-300. 



c. The Sparing Action of Vitamin E on Vitamin A and the Carotenoids. 



*i3 V. N. Krukovsky, J. K. Loosli, and F. Whiting, J. Dairy Set., 32, 196-201 (1949). 

 *!■* J. Nielsen, A. N. Fisker, A. H. Pedersen, I. Frange, E. S0ndergaard, and H. Dam, 

 J. Dairy Research, 20, 333-339 (1953). 



"6 E. M. Bradway and H. A. Mattill, J. Am. Chem. Soc, 66, 2405-2408 (1934). 



