The effect of the composition of butterfat on its susceptibility of oxidation

Summary There is considerable variation in the stability of the butter fat toward oxidation where it is obtained from different cows and from an individual cow at different periods. The stability of butterfat toward oxidation bears an inverse relation to the unsaturation of the fat. The fat from cows receiving grass as part of their ration is less saturated and more susceptible to oxidation. It appears that the amount of linoleic acid rather than the oleic acid governs the stability of butterfat. The results point to the presence of protective substances in milk in increased amounts when cows are on grass which prevent the development of oxidized flavors in the milk. There is no relation between the carotene content, as evidenced by the color of the fat, and the stability of the fat toward oxidation. The refractive index of butterfat varies in direct proportion to the iodine number of the fat.