EFFECTS OF STORAGE AND VARIOUS INTRINSIC VITAMIN-E CONCENTRATIONS ON LIPID OXIDATION IN DRIED EGG POWDERS

Supplementing the diets of laying hens with 0, 25, 50, 75, 100, and 200 mg of all-rac-alpha-tocopheryl acetate (vitamin E) per kg of feed increased the concentration of this antioxidant in the eggs in a dose-dependent manner. Storage of spray-dried whole-egg powders at ambient temperature for up to 18 months resulted in gradual losses of vitamin E after 6 months, with the greatest losses occurring in those powders with the highest initial content. Marked changes in the concentration of products of lipid peroxidation (thiobarbituric acid reactive substances (TBARS), free fatty acids, oxidised fatty acids, peroxide values, oxysterols) occurred during the storage period which generally correlated inversely with the vitamin E content of the powder. The appearance, and sometimes disappearance, of the products with storage time varied with the individual product. Oxidised fatty acids appeared at 0-2 months, free fatty acids at 4-8 months and TBARS at 8-12 months. 25-Hydroxycholesterol and cholestan-3,5,6-triol appeared at 2 months, peaked between 4 and 6 months and disappeared by 8 months. 7beta-Hydroxycholesterol, 7-ketocholesterol and cholesterol-5,6-epoxide appeared at 4 months, peaked at 8-12- months and markedly declined by 18 months. Ingestion of certain lipid peroxidation products, particularly oxysterols which are generally regarded as cytotoxic, could be detrimental to health. Methods for preventing oxysterol formation in commercially prepared and stored foods by simply increasing the intrinsic vitamin E concentration of eggs, which are a major source of cholesterol, would benefit the food industry and human health.