Formation of protein-rich coatings around lipid droplets using the electrostatic deposition method.

The purpose of this study was to determine whether protein-rich coatings could be formed around lipid droplets using an electrostatic deposition method. These coatings were assembled using two methods: (i) beta-lactoglobulin was adsorbed to beta-lactoglobulin-pectin-coated lipid droplets; (ii) beta-lactoglobulin-pectin complexes were adsorbed to beta-lactoglobulin-coated lipid droplets. Composite particles, consisting of lipid droplets with protein-rich biopolymer coatings, could be formed using both approaches (e.g., at pH 4, the protein surface load could be increased from 3 to 59 mg m(-2)). These composite particles could be made small (d < 500 nm) and relatively stable to gravitational separation at certain protein concentrations. Nevertheless, aggregation and sedimentation occurred at sufficiently high protein concentrations because of charge neutralization. The composite particles remained stable after they were heated above the thermal denaturation temperature of the globular proteins at pH 4. When the heated composite particles were adjusted to pH 7, where beta-lactoglobulin and pectin are both negatively charged, some of the pectin and beta-lactoglobulin became detached from the droplet surfaces but the protein surface load was still higher than in a nontreated sample. These composite particles may be useful for increasing the protein concentration in biopolymer coatings surrounding lipid droplets, which potentially has practical applications in the food industry (e.g., in protecting omega-3 oils from oxidation or in developing natural weighting agents).