Optimisation of extraction conditions for phenolic compounds from limau purut (Citrus hystrix) peels

The objective of this study was to optimise the extraction conditions for phenolic compounds from limau purut (Citrus hystrix) peels using response surface methodology (RSM). A central composite rotatable design (CCRD) was applied to determine the effects of ethanol concentration (%), extraction temperature (oC), and extraction time (min) on total phenolic content (TPC) from limau purut (Citrus hystrix) peels. The independent variables were coded at five levels and their actual values were selected based on the results of single factor experiments. Results showed that ethanol concentration was the most significant (p<0.001) factor affecting the TPC. The optimum extraction conditions were found to be ethanol concentration of 52.9%, extraction temperature of 48.3oC, and extraction time of 126.5 min. Under the optimised conditions, the experimental value for TPC was 1291.8 mg GAE/100g DW, which reasonably close to the predicted value (1268.8 mg GAE/100g DW).