Influence of Linoleic Acid Content of Milk Lipids on Oxidation of Milk and Milk Fat

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Abstract
The concentration of linoleic acid in milk lipids was increased by infusing two cows with a cottonseed oil emulsion, and changes in the oxidative stability of the milk and milk fat were determined. Infusing 150g of cottonseed oil (as Lipomul I. V.) tripled the linoleic acid content of the milk fat in the next milking. Linoleic acid in the milk phospholipids increased to a smaller extent, and not until the second milking after the infusion. Little change was noted in the concentration of other fatty acids. No significant change occurred in milk production, fat percentage, or the amounts of Cu, tocopherols, and carotenoids. A decrease in oxidative stability of the milk fat appeared to be related to the increase in its linoleic acid content. Furthermore, an increase in susceptibility of the milk to copper -induced oxidized flavor, as measured by the thiobarbituric acid test, appeared to be dependent on increased linoleic acid content of the phospholipids rather than the milk fat.