Modification of emulsion properties by heteroaggregation of oppositely charged starch-coated and protein-coated fat droplets

The manuscript describes the formation and characterization of emulsions formed by controlled heteroaggregation of oppositely charged fat droplets coated by either cationic whey protein isolate (WPI) or anionic modified starch (MS). Heteroaggregation was induced by mixing two the oppositely charged 20 wt% oil-in-water emulsions together (d43 ≈ 380 nm) at pH 3.5. The mean particle diameter, electrical charge, and micro-structure of the heteroaggregates formed were measured as a function of negative-to positive particle ratio (0–100%) and pH (2.5–6.5). WPI-coated fat droplets were positive below pH 5.5 and negative above this value, while MS-coated fat droplets were negatively charged across the entire pH range. Upon mixing the two types of fat droplets together we found that the largest aggregates and highest viscosity occurred at a particle ratio of 70% MS and 30% WPI, which was attributed to strong electrostatic attraction between the oppositely charged droplets. The heteroaggregates partly dissociated at certain pH values, which was attributed to weakening of the electrostatic attraction between the different droplets. Heteroaggregates formed by oppositely charged fat droplets may be useful for creating specific food structures that lead to desirable physicochemical properties, such as enhanced viscosity at low fat content.