Ultrasonic Fabrication of Catechin Nanoemulsions from Green Tea with Enhanced Stability and Antioxidant Activity Optimized by Box-Behnken Design

Nanoemulsions are emulsions, either O/W (oil in water) or W/O (water in oil), with droplet diameters typically ranging from 50 to 1,000 nm. Research indicates that nanoemulsions are highly effective in enhancing the bioavailability, bioactivity, digestibility, stability, safety, quality and sensory attributes of food components. The study aimed to determine the optimum formulation and ultrasonic condition for fabricating catechin nanoemulsion (Ca-NE) from green tea with improved physical stability and antioxidant activity using response surface methodology. The effects of Medium Chain Triglyceride oil concentration (7.5 - 12.5 % w/w), Tween® 80 concentration (1 - 5 % w/w) and sonication time (5 - 15 min) on the droplet size, polydispersity index (PDI) and antioxidant activity presented by DPPH value of the Ca-NE were investigated using Box-Behnken design (BBD). The results found that droplet size and antioxidant activity of the Ca-NE were significantly (p < 0.05) affected by the proposed parameters, whereas the PDI value was slightly affected by those factors. The BBD results suggested that the Ca-NE fabrication condition was optimized with 7.5 % (w/w) oil concentration, 5 % (w/w) Tween® 80 concentration and a sonication time of 10.87 min. The optimum nanoemulsion showed good physical stability in terms of droplet size and PDI and had higher antioxidant activity than unencapsulated catechins when stored at 4 and 30 °C for 90 days. This study showed that catechin nanoemulsions fabricated by ultrasonication had good stability and antioxidant activity and, hence, had high potential for food and beverage applications in the food industry. HIGHLIGHTS The optimum nanoemulsion had good physical stability regarding droplet size and PDI when stored at 4 and 30 °C for 90 days. The ultrasonic fabrication of Ca-NE results in better retention of antioxidant activity than unencapsulated catechins. The ultrasonic fabrication provided the Ca-NE with good stability and high antioxidant activity. The results suggest that the obtained nanoemulsion of catechins has great potential in food or pharmaceutical applications. GRAPHICAL ABSTRACT