Cholecalciferol- and α-tocopherol-loaded walnut oil emulsions stabilized by whey protein isolate and soy lecithin for food applications

BACKGROUND To overcome the limitations in the use of protein as an emulsifier, soy lecithin, a natural surfactant, was used along with whey protein isolate (WPI) to produce o/w emulsions containing cholecalciferol and alpha-tocopherol. The physical stability of the emulsions prepared with WPI and varying concentrations of lecithin (0, 1, 2, and 3% w/w) was measured in different heat, pH, and ionic-strength food environmental conditions. RESULTS All emulsions were shown to be less than 250 nm in size and less than 0.3 in polydispersity index (PDI). The morphology of the emulsions was spherical, and the droplets of the emulsion containing lecithin were thicker and larger than those of the emulsion without lecithin (WPI_L0). After autoclaving, WPI_L0 increased in size from 197.8 +/- 1.7 nm to 528.5 +/- 28.4 nm, and the retention of cholecalciferol and alpha-tocopherol decreased to 40.83 +/- 0.63% and 49.68 +/- 1.84%, respectively. At pH 5.5, near the isoelectric point of WPI, WPI_L0 increased in size due to aggregation, but emulsions containing lecithin remained stable at a PDI under 0.3. Turbiscan stability index of the emulsion prepared with WPI and 3% lecithin was the lowest, indicating good storage stability. In addition, it was confirmed that the higher the lecithin content, the higher the viscosity, and the higher the amount of free fatty acids released in the in vitro digestion model. CONCLUSION This study can provide theoretical evidence for enhancing the physical stability of protein emulsions by co-stabilization with lecithin, promoting their application in various foods. (c) 2022 Society of Chemical Industry.

Automated summary

This study confirms that the physical stability of protein emulsions can be enhanced by co-stabilizing with lecithin, promoting their application in various foods. The emulsions have a particle size of less than 250 nm and a polydispersity index of less than 0.3. The higher the lecithin content, the higher the viscosity and the higher the amount of free fatty acids released in the in vitro digestion model.