Valorisation of agricultural by-product: Optimisation of alcohol-based extraction of polyphenols from chestnut peel using Box-Behnken Design

Abstract

In the present work, solvent concentration, extraction time, and solid to solvent (S/S) ratio were evaluated in order to recover the majority of polyphenols from chestnut peel waste using ethanol and methanol. Extraction method for polyphenols from peel pre-treated by ohmic heating (OH) was optimised using response surface methodology (RSM). The effect of these independent variables on total phenolic content (TPC) and antioxidant capacity (AC) was studied using Box-Behnken Design (BBD). A second-order polynomial model provided a satisfactory fit to the experimental data with a high coefficient of determination (R2) value. Results showed that S/S ratio and solvent concentration were generally significant variables during extraction in terms of TPC and AC. The optimum extraction conditions were obtained as 1/10 of S/S ratio and 60% of solvent concentration for both solvents. As the optimum extraction time, 82.41 min for ethanolic extraction and 116.97 min for methanolic extraction were selected. Under these optimal conditions, TPC values of the ethanolic and methanolic extracts were found to be 39.02 and 38.79 mg gallic acid equivalents per gram of dry matter (mg GAE/g DM), respectively, thus indicating highly close agreement to the predicted values. Consequently, the effectiveness of the solvents used was found to be very similar to each other. The OH pre-treatment appeared to be a promising technique for polyphenolic extraction from industrial wastes.