Preparation of multiple emulsions based on thermodynamic incompatibility of heat-denatured whey protein and pectin solutions

This study shows that various types of multiple emulsions can be prepared by mixing an oil-in-water emulsion with a mixed biopolymer solution that separates into two phases. Initially, a phase diagram was prepared to identify the range of heat-denatured whey protein isolate (HD-WPI) and pectin concentrations where phase separation occurred. Under certain conditions the biopolymers formed a two-phase system consisting of a HD-WPI-enriched lower phase (W1) and a pectin-enriched upper phase (W2), which was attributed to thermodynamic incompatibility to the two biopolymers. Water-in-water emulsions (W1/W2 or W2/W1) could be formed by blending incompatible upper and lower phases together at different ratios. We then showed that whey protein stabilized oil droplets preferentially partition into the HD-WPI rich phase of two-phase biopolymer systems. This enabled us to prepare multiple emulsions by mixing a whey protein stabilized oil-in-water emulsion with incompatible upper and lower phases. These multiple emulsions were either of the oil-in-water-in-water (O/W1/W2) type or the mixed oil-in-water/water-in-water (O/W1–W2/W1) type depending on the initial biopolymer composition of the system. Multiple emulsions may prove useful for the creation of food emulsions with improved physicochemical properties or for the development of novel delivery systems.