Improving the oxidative stability of model whey protein hydrolysate-based infant formula emulsions with lecithin

Oil-in-water emulsions containing 1.55, 3.50 and 7.00%, w/v, protein (whey protein hydrolysate), soya bean oil and carbohydrate, respectively, and 0-5% lecithin, w/w oil, were prepared and stored for 14 days at 40 degrees C. Oxidative stability of bulk oil (0-5% lecithin) and emulsions was measured using Rancimat and using peroxide and TBARS assays, respectively. The oxidative stability of bulk oils increased with increasing lecithin concentration. In emulsions, lecithin addition at 1%, w/w oil, retarded lipid oxidation, while adding lecithin at 2-5% showed no additional effect. The antioxidant effect of the lecithin, in both bulk oil and emulsions, was associated with its surface activity and ability to bind free radicals and pro-oxidants.