Synergy evaluation of flavonoid glycosides from Camellia oleifera cake and ionic surfactants on the stability of oil-in-water emulsions

Compared with synthetic surfactants, amino acid surfactants (sodium N-lauroylsarcosinate, SLS) and natural products (flavonoid glycosides from Camellia oleifera cake, FG) have renewability, lower toxicity, and biodegradability, which can reduce energy consumption and environmental pollution during emulsion preparation. Storage time and lipid oxidation are important indicators for evaluating the environmental adaptability of emulsions. However, the effect of complex systems (surfactants and flavonoids) on emulsion performance and its related mechanisms have not yet been thoroughly studied. The oxidative stability, physical stability, and interaction mode of FG-ionic surfactants (SLS/CTAB)-stabilized oil-in-water (O/W) emulsions were explored. The results indicated that FG displayed excellent antioxidant and emulsifying capacity without negative hemolysis. Moreover, FG contributed to the interfacial activity of ionic surfactants. The optimum synergistic ratio of SLS/ CTAB-FG was 0.167/0.091. The presence of FG alleviated the stratification of cream volume and retarded Ostwald ripening and droplet coalescence. After storage, the FG-SLS-stabilized emulsions showed the smallest droplet size and the largest emulsion volume. Moreover, the addition of FG effectively reduced the production of harmful substances such as 2-thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides. A meaningful discovery was that oxidative stability depended strongly on the interaction mechanism between FG and surfactants. FG was more useful for improving the oxidative stability of anionic surfactant-stabilized emulsions. Overall, this study demonstrates that Camellia oleifera cake can serve as an inexpensive and ecofriendly renewable resource for natural emulsifiers and antioxidants, and provides theoretical guidance for its more effective utilization.