Synergistic stabilization of heat-treated emulsions containing mixtures of milk proteins

The synergistic effect by which a very small amount of casein can confer stability to a whey protein-stabilized emulsion heated to 90 °C has been investigated. Using β-lactoglobulin (β-lg) as the main emulsifying agent, the extent of heat-induced flocculation increased with ionic strength, with commercial sodium caseinate or β-casein incorporated. The protective effect of casein was retained for a moderate concentration of ionic calcium. Casein added before heating, or shortly afterwards (i.e. before the emulsion had cooled), offered substantial synergistic protection to the heated β-lg-stabilized emulsion. With α-lactalbumin (α-la) as the primary emulsifying agent, no significant protective effect could be observed. In contrast, casein could confer significant stability to a heat-treated bovine serum albumin emulsion. Quiescent storage stability testing suggests that a combination of limited heating and casein addition could improve the long-term shelf-life of a whey protein-based emulsion.