Whey protein stabilized nanoemulsion: A potential delivery system for ginsenoside Rg3 whey protein stabilized nanoemulsion: Potential Rg3 delivery system

In the current research, we systematically investigated the physicochemical stability of the nanoemulsions that were formulated with 90% (v/v) whey protein isolate (WPI) aqueous phase and 10% (v/v) medium chain triglyceride oil phase at neutral pH using high intensity ultrasonication. We measured the physicochemical properties of nanoemulsions stabilized by WPI at different concentrations, including particle size, zeta potential, turbidity, centrifugal stability, and rheological behavior. Besides, we also evaluated the influence of processing conditions (ionic strength, freeze-thaw cycle and thermal treatment) on the nanoemulsion stability. The particle size of WPI nanoemulsions increased by approximately 5% at 25 degrees C and 8% at 37 degrees C after 7 weeks' storage, while the particle size and zeta potential of the nanoemulsions at 4 degrees C were changed. The 1% WPI stabilized nanoemulsion was very sensitive to Na+ (0.1-0.5 mol/l) and freeze-thaw treatment (3 cycles) with significant increase in particle size and decrease in the absolute value of zeta potential. The turbidity of nanoemulsions decreased by over 50% after freeze-thaw cycles, especially the 1% WPI stabilized nanoemulsion. All samples were still stable under thermal conditions. Among them, the 5% WPI stabilized nanoemulsion showed the best ionic, freeze-thaw, and thermal stability. All tested nanoemulsions showed typical shear-thinning behavior, and the infinite shear viscosity of 5% WPI stabilized nanoemulsions was highest. In conclusion, the 5% WPI stabilized nanoemulsion has the best physicochemical stability under different processing conditions during storage, which has high potential in use as a delivery system for bioactive substances like ginsenoside Rg3 in food technology.