Abstract: In this paper, the in vitro digestion patterns of naringin-loaded monolayer and bilayer nanoemulsions constructed by using whey protein isolate (WPI) alone and in combination with ι-carrageenan (ι-Car) or gum arabic (GA) as emulsifiers, named as NA/WPI-e, NA/WPI/ι-Car-e and NA/WPI/GA-e, respectively were studied. The analysis of droplet size, zeta potential and microstructure during simulated gastrointestinal digestion indicated both the single and bilayer nanoemulsions underwent different degrees of hydrolysis. During simulated gastric digestion, the emulsion droplets aggregated, resulting in a significant increase in their average particle size (P < 0.05), and the zeta potential absolute value also increased. During simulated intestinal digestion, deflocculation of the naringin-loaded nanoemulsions was observed. After simulated gastrointestinal digestion, the release rate of free fatty acids (FFAs) and naringin bioavailability of NA/WPI-e were 97.3% and 10.06% respectively. The FFA release rate and naringin bioavailability of NA/WPI/ι-Car-e were lower than those of NA/WPI-e, while NA/WPI/GA-e at 1 mg/mL GA concentration showed the highest naringin bioavailability (12.13%). The FFA release rates of the single and bilayer nanoemulsions were significantly higher than that of the control group (34%), indicating that the nanoemulsion delivery system can effectively improve the bioavailability of naringin.

Key words: in vitro simulated digestion; naringin; nanoemulsion; digestion characteristics