Effect of NaCas/Tween 80 ratios and environmental stresses on the physical stability of perilla oil-in-water emulsions

In order to enlarge the application of perilla leaf oil, we investigated the effect of sodium caseinate (NaCas)/Tween 80 ratios, pH, NaCl concentration, and storage temperature on the physical stability of perilla oil-in-water emulsions. A decrement in average particle size and an increment in zeta-potential were observed with decreasing NaCas/Tween 80 ratios, but the Turbiscan stability index (TSI) value was the lowest (0.4) at a NaCas/Tween 80 ratio of 4:6. The average particle size and TSI increased with increasing storage temperature (4–55 °C), and the increases were greater at pH 4.0 and 5.0 than that between 2.0–3.0 and 6.0–10.0, but the average particle size and TSI were largely independent of NaCl concentration (0–800 mM). The PO/W emulsion was susceptible to aggregation at pH values close to the isoelectric point of the NaCas (pH 4.0 and 5.0), at high NaCl concentration (800 mM), and at accelerated storage temperatures (55 °C). These results provide practical information for mix-use of proteins (NaCas) and nonionic surfactants (Tween 80) to stabilize perilla oil-in-water emulsions and the application of these emulsions within pharmaceutical, beverage, and food products. Practical Applications The results obtained from this research should be helpful for designing perilla oil-in-water emulsions that are stabilized by different ratios of sodium caseinate to Tween 80 and remain stable in certain environments, thereby enlarging the application of perilla oil in pharmaceutical, food, and beverage industries.