Enzymatic hydrolysis of milk proteins used for emulsion formation .2. Effects of calcium, pH, and ethanol on the stability of the emulsions

Oil-in-water emulsions were prepared with native milk proteins (caseinate and beta-lactoglobulin) or the same proteins after different extents of breakdown by treatment with trypsin. The effect of trypsin treatment of the emulsions after formation was also investigated. The stability of emulsions was measured by determining the particle sizes with light scattering. Different destabilization conditions were used; namely, decreasing pH, adding calcium ions, or incorporation of ethanol. Comparisons were made between emulsions containing modified and unmodified proteins. Trypsinolysis rendered caseinate emulsions less stable to decreasing pH and increasing concentrations of ethanol, but the stability to calcium increased and correlated with the surface composition of individual types of casein molecules and their calcium sensitivity. Emulsions containing beta-lactoglobulin, on the other hand, showed improved stabilities with hydrolysis under all conditions compared with emulsions containing unhydrolyzed protein.