Optimization of microwave-assisted extraction and the effect of microencapsulation on mangosteen (Garcinia mangostana L.) rind extract

Abstract

The effects of optimization of microwave-assisted extraction (MAE) and microencapsulation on the total xanthone content (TXC), total phenolic content (TPC), and antioxidant activity of mangosteen rind extract were studied. Response surface methodology (RSM) was employed with Box-Behnken design to generate fifteen optimization responses by incorporating three independent variables, namely soaking time, solvent-to-feed (S/F) ratio and extraction time. The highest extraction yield (19.43%) was obtained in the third response. TXC and TPC results fitted well, with high R-squared values (0.83-0.91), into the generated models, but not the antioxidant activity data. The interactive effects of S/F ratio and extraction time significantly increased the yields of TXC (46.62 mg α-mangostin/g crude extract) and TPC (46.30 mg gallic acid equivalent/g crude extract), but longer soaking time showed adverse effect. All the results obtained from the optimized models were validated using experimental data which showed desirability index of 0.88. The optimized parameters of MAE were established as 20:1 S/F ratio and 9 min extraction time, without soaking process. Despite the intact morphology of microcapsules observed, spray drying microencapsulation only preserved TXC partially (63.54%) but denatured more than 85% of TPC. Future investigation on the microencapsulation of mangosteen rind extract is required.