Effects of Solanum torvum fruit saponin content and processing conditions on stability of Bacopa monnieri and virgin coconut oil -in-water emulsion

Abstract

The study aimed evaluate the application of saponins from Solanum torvum fruits (STS), as a natural emulsifier for an oil-in-water emulsion containing Bacopa monnieri extract (BME) and virgin coconut oil (VCO). STS (0.1% to 1.0 % w/w) was homogenized at 15,000 rpm for one minute along with previously optimized BME and VCO contents. Emulsions were pasteurized at 85 ºC. Emulsification index (EI), turbidity (T), centrifuged emulsion stability (ES), droplet diameter and distribution (DD) and oil content in the emulsified region (OC) were analyzed. Selected STS contents were further processed with BME and VCO under varying conditions including homogenization speed, pH, heating temperature and salt concentration. Emulsions containing STS showed better emulsification compared to controls. EI, T, ES, DD and OC were significantly higher (p<0.05) in emulsions containing 0.5 % to 1.0 % STS compared to those with 0.1 % to 0.25 % STS. Similar increasing emulsification trends were observed in both raw and pasteurized emulsions. Pasteurization caused an immediate reduction in EI, T, ES and an increase in droplet diameter; however, these changes were minimal in emulsions with 0.5 % to 1.0 % STS. Increasing homogenization speed from 5000 rpm to 20 000 rpm and heat treatment at 90 ºC increased EI, T, ES and OC. These parameters also increased above the emulsion’s natural pH but decreased at pH levels below 4.0. Addition of 0.05 % NaCl and above significantly reduced (p<0.05) stability parameters. In conclusion, STS is a potential emulsifier in BME-added VCO-in water emulsions, providing significant emulsification effects at 0.5 % to 1.0 % concentrations. Its stability decreases below pH 4.0 and with NaCl addition, while increased homogenization speed improves stability.