Heat stability of milk emulsions: phospholipid–protein interactions

Abstract

Abstract Certain types of lecithin increase the heat stability of recombined and conventional full-cream evaporated milk but the mechanism is unknown. Previous studies have indicated the importance of fat in the system. New studies have indicated the nature of protein–lecithin interactions involved in improving heat stability. Two likely mechanisms were considered: (a) that lecithin increases heat stability by displacement of or by interaction with surface-adsorbed protein and (b) that lecithin interacts with free protein in solution thereby influencing heat-induced free protein/bound protein interactions. These possibilities were investigated by examining the effect of lecithin on the heat stability of fresh whole milk, unhomogenized and homogenized, and the corresponding skim milk and recombined milk in the absence and presence of indigenous serum protein. Lecithin does not require fat per se to affect heat stability. In addition, it does not exercise its effect on heat stability by interaction with free protein in solution but changes heat stability by targeting the membrane proteins. These findings were obtained for lecithins containing non-acidic and acidic phospholipids.