Properties and Stability of Perilla Seed Protein-Stabilized Oil-in-Water Emulsions: Influence of Protein Concentration, pH, NaCl Concentration and Thermal Treatment

Perilla seed protein (PSP) was extracted from defatted perilla seed meal and applied in oil-in-water (O/W) emulsions as an emulsifier. We investigated the influences of protein concentration (0.25-1.5 wt %), pH (3.0-9.0), NaCl concentration (0-350 mmol/L) and thermal treatment (70-90 degrees C, 30 min) on the physical characteristics of O/W emulsions, including volume-average diameter, zeta-potential, interfacial protein concentration, microstructure and so on. Results showed that increasing PSP concentration would decrease the d(4,3) and a 1.0 wt % PSP concentration was sufficient to ensure the stability of emulsion. Under pH 3.0-9.0, emulsions were stable except at pH 3.0-5.0 which was proximal to the isoelectric point (pH 4.5) of PSP. At high NaCl concentrations (250-350 mmol/L), the emulsions exhibited relatively lower absolute zeta-potential values and a large number of aggregated droplets. A moderate thermal treatment temperature (e.g., 70 degrees C) was favorable for the emulsion against aggregation and creaming. However, when 90 degrees C thermal treatment was performed, a clear layer separation was observed after 2 weeks storage and the emulsion showed a poor stability. The findings of this work are of great importance for the utilization and development of PSP as an emulsifier for food emulsions.