The difference in transfer of all-rac-α-tocopherol stereo-isomers to milk from cows and the effect on its oxidative stability

Experiments were conducted to study the effect of all-rac-α-tocopheryl acetate supplementation of the diet of dairy cows on the oxidative stability of milk. In experiment I the cows’ feed was supplemented with 2600 IU per day per cow and in experiment II with 3400 IU and high amounts of unsaturated fat to get the milk more susceptible to oxidation. The content of α-tocopherol in milk was determined before and after supplementation, and the percentage increase of α-tocopherol in the milk in the two experiments was 37% and 29%, respectively. The native stereo-isomer (RRR-α-tocopherol) made up 84.3% (experiment I) and 88.8% (experiment II) of the isomers, indicating that transfer of the synthetic stereo-isomers to the milk was low. The milk was further exposed to fluorescent light or added copper. Milk with a high content of unsaturated fatty acids and high concentrations of α-tocopherols was more susceptible to oxidation than the milk with low α-tocopherol content.