Preparation of W/O/W double nanoemulsions loaded by red dragon fruit extract

Abstract

Betacyanin, the major compound in red dragon fruit extract is a high value bioactive polyphenol compound with wide application in functional food. This bioactive compound is very sensitive to oxidation and has low bioavaibility. In this research, we prepared w/o/w nanoemulsion encapsulating hydrophilic betacyanin using two-step high energy emulsification. Polyglycerol polyricinoleate (PGPR) as hydrophobic surfactant, soya bean oil, red dragon fruit extract, ultraturrax (10,000 rpm, 3'), ultrasonic (20 KHz, 5') were used for primary water in oil (w/o) emulsification. The influence of PGPR concentration and sonification time on the droplet size and Poly Dispersity Index (PDI) of the fabricated w/o primary emulsion was investigated. The results showed that PGPR concentration affected significantly on droplet size and PDI of w/o primary emulsion. The selected w/o primary emulsion (A3B3) was emulsificated with aqueous phase (20:80) and 1% w/w Tween 80 using High Pressure Homogenizer at 200 Bar, 3 cycles and formed w/o/w nanoemulsion with the following characteristics: droplet diameter was 199 nm; PDI was 0.18; zeta potential was-37.1 mV. The antioxidant activity of this w/o/w nanoemulsion applying the DPPH method was 9.15 ppm for betacyanin. It has been observed that betacyanin in nanoemulsion (0.068 %w/w) performed antioxidant activity 3.5% from betacyanin content in natural extract (0.34%). Hence, betacyanin loaded in w/o/w nanoemulsion was better as an antioxidant natural red dragon fruit extract.