Heteroaggregation of lipid droplets coated with sodium caseinate and lactoferrin

- Heteroaggregates formation with oppositely charged lipid droplets was investigated.
- Their properties depended on droplets volume ratio and protein properties.
- Improved rheological properties can be obtained compared to a single emulsion.
- Heteroaggregates with gel like behavior were obtained depending on protein ratio.
- Heteroaggregates were not affected to salt addition.

Formation and characterization of droplet heteroaggregates were investigated by mixing two emulsions previously stabilized by proteins oppositely charged. Emulsions were composed of 5 vol.% of sunflower oil and 95 vol.% of sodium caseinate or lactoferrin aqueous dispersions. They were produced using ultrasound with fixed power (300 W) and sonication time (6 min). Different volume ratios (0-100%) of sodium caseinate-stabilized emulsion (droplet diameter around 1.75 μm) to lactoferrin-stabilized emulsion (droplet diameter around 1.55 μm) were mixed under conditions that both proteins showed opposite charges (pH 7). Influence of ionic strength (0-400 mM NaCl) on the heteroaggregates stability was also evaluated. Creaming stability, zeta potential, microstructure, mean particle diameter and rheological properties of the heteroaggregates were measured. These properties depended on the volume ratio (0-100%) of sodium caseinate to lactoferrin-stabilized emulsion (C:L) and the ionic strength. In the absence of salt, different zeta potential values were obtained, rheological properties (viscosity and elastic moduli) were improved and the largest heteroaggregates were formed at higher content of lactoferrin-stabilized emulsion (60-80%). The system containing 40 and 60 vol.% of sodium caseinate and lactoferrin stabilized emulsion, respectively, presented good stability against phase separation besides showing enhanced rheological and size properties due to extensive droplets aggregation. Phase separation was observed only in the absence of sodium caseinate, demonstrating the higher susceptibility of lactoferrin to NaCl. The heteroaggregates produced may be useful functional agents for texture modification and controlled release since different rheological properties and sizes can be achieved depending on protein concentrations.

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