Effect of emulsifiers and fortification methods on light stability of vitamin A in milk

Lowfat milk is commercially fortified during processing by adding small quantities of oil containing an emulsifier and vitamin A. Added vitamin A is degraded more rapidly than indigenous vitamin A when milk is exposed to light. The objective of this research was to determine if added vitamin A could be made as stable to light as naturally occurring vitamin A by placing it in the more dilute milk fat environment with naturally occurring emulsifiers. Using HPLC to quantify retinyl palmitate, the effect of emulsifiers indigenous to milk versus a commercial emulsifier was first investigated. Butter serum, rich in fat globule membrane material, was compared with Durfax 80 in a 1% recombined milk system. No difference was found in vitamin A stability to light due to emulsifier type. A second experiment on 1% milk compared light stability of vitamin A added in concentrated milk fat emulsion, vitamin A added to all the milk fat, and indigenous vitamin A. Indigenous vitamin A and vitamin A added to all the fat were equally stable and more stable than vitamin A added in a concentrated milk fat emulsion.