Whey protein isolate-stabilized gardenia fruit oil nanoemulsions: Ultrasonic preparation, characterization and applications in nutraceuticals delivery

In the current research, ultrasound was applied to make whey protein isolate (WPI)-gardenia fruit oil nanoemulsion. Effects of preparation conditions on physicochemical characteristics of nanoemulsions were investigated. The smallest droplet size was obtained at the oil content of 10% (v/v) and the WPI concentration of 0.5% (w/v) with ultrasound (2.4 W/mL, 12 min). Ultrasound led to a more uniform nanoemulsion with smaller droplet sizes (< 300 nm). The nanoemulsion prepared with ultrasound remained relatively stable for more than one week, while the crude emulsion prepared without ultrasound layered after 1 day storage. The nanoemulsion was more stable at lower temperature, alkaline condition and lower Na+ concentration. The formation of nanoemulsions significantly reduced the generation rate and amount of POV and TBARS during the 14-day accelerated oxidation experiment, increasing the oxidation stability of gardenia fruit oil. Additionally, the nanoemulsion could encapsulate β-carotene, hesperetin and naringenin at the efficiency of 79.61%, 51.29% and 46.06%, which further improved the oil oxidation stability and retarded free fatty acids release during the stimulated digestion in vitro.