Optimization of process variables using response surface methodology for tocopherol extraction from roselle seed oil by supercritical carbon dioxide

Abstract

Hibiscus sabdariffa L. (Roselle) seeds are rich in proteins, carbohydrates and unsaturated fatty acids, and are a good source of minerals and antioxidants. Supercritical carbon dioxide (SC-CO2) extraction was applied for extraction of oil from Roselle seed at temperatures of 40 °C to 80 °C and pressures of 20 MPa to 30 MPa. The effects of temperature and pressure on the extraction yield and solubility of oil were determined. Process optimization was carried out using response surface methodology (RSM). A particle size of 300 μm, SC-CO2 flow rate of 5 mL/min and extraction time of 180 min were held constant throughout this study. The overall oil yield increased as pressure and temperature was increased, while a reverse effect was observed at higher temperatures. The optimum extraction conditions for Roselle seed oil corresponded to a pressure of 30 MPa and temperature of 40 °C. According to the analysis of variance (ANOVA), the coefficient of determination R2 for oil yield and gamma tocopherol concentration were 0.9723 and 0.9754, respectively, indicating a good correlation and agreement between the experimental and predicted values.