Reducing off-flavors in plant-based omega-3 oil emulsions using interfacial engineering: Coating algae oil droplets with pea protein/flaxseed gum

Algae oil is a sustainable source of health-promoting docosahexaenoic acid (DHA) suitable for vegans and vegetarians, but it has poor water-solubility and is prone to lipid oxidation, which leads to unpleasant off flavors. In this research, emulsion technology was used to create a plant-based DHA delivery system consisting of algae oil droplets coated by pea protein (PP) and flaxseed gum (FG). The pea protein was used as an emulsifier, while the flaxseed gum was deposited onto the protein-coated droplets by electrostatic deposition. The PP-FG interactions were investigated in solution and at the oil-water interface. Stable PP/FG-coated oil droplets were formed when the FG concentration was high enough to saturate the PP-coated droplet. Transmission electron microscopy showed that the interfacial thickness increased with increasing FG concentration. The oil-water interfacial tension of the PP/FG complex (14.6 nN/m) was slightly lower than that of the PP alone (18.7 nN/m), which suggests that the presence of the polysaccharide increased the surface activity. Furthermore, analysis of headspace volatiles showed that the presence of the interfacial coating could reduce the undesirable fishy smell of algae oil, i.e., low heptanal and (E, Z)-3,5-octadiene-2-one levels. This phenomenon was attributed to the ability of the interfacial coatings to inhibit lipid oxidation or reduce off flavor release from the oil droplets. The plant-based emulsions produced in this study may therefore be suitable as effective ω-3 fatty acid delivery systems that can be incorporated into functional foods and beverages.