Optimization of microwave-assisted extraction of cocoa bean shell waste and evaluation of its antioxidant, physicochemical and functional properties

Abstract

Cocoa bean shell (CBS) waste is obtained in large amounts in chocolate production. In this work, microwave-assisted extraction (MAE) of CBS was used and experimental parameters were optimised by using response surface methodology. Effects of pH, time, temperature and solid:liquid ratio were evaluated on the extraction yield, total uronic acid content, total phenolic content (TPC) and antioxidant performance. A great influence of pH on the CBS extraction was observed, since alkaline conditions resulted in higher extraction yields and antioxidant capacity. Optimal MAE conditions were determined as 5 min, pH 12, 97 °C and S/L 0.04 g/mL showing better outcome than conventional solvent extraction. Antioxidant performance was evaluated by using colorimetric methods (FRAP, ABTS) while structural (FTIR), physico-chemical and functional properties of the MAE extracts were also determined. MAE extracts obtained at pH 12 were rich in proteins (580.0 mg BSA/g), polysaccharides (370.4 mg Glu/g) and polyphenols (35.9 mg GAE/g), showing important antioxidant performance (35.5 mg TE/g). It can be concluded that MAE is an efficient technique for the release of bioactive molecules from CBS with antioxidant performance and potential applications in the food industry.