Towards a scalable cacao pod husk biorefinery: Understanding the effects of process conditions on phenolic antioxidant extraction and residual solid properties

Abstract

Cacao pod husk (CPH) is a potential source of phenolic-based antioxidants and lignocellulosic compounds. Sample pretreatments and extraction conditions were investigated to understand their effects on extraction yields and implications for industrial-scale CPH biorefinery. All processing parameters showed significant effects (p-value < 0.001) on extraction yields, where solvent selection and size reduction were the most influential parameters (η2 > 0.92). CPH extracts contained 3.3–215.1 mg GAE/g dw of phenolics, 0.01–0.38 mg Cy3GE/g dw of anthocyanin and 0.86–22.5 mg TE/g dw of antioxidant activity, making it useful as antioxidants. CPH solid residues, rich in lignocellulosic compounds (23 % of lignin, 37 % of cellulose and 22 – 26 % of hemicellulose), volatile matter (62–65 %) and fixed carbon (21–25 %), are promising as pyrolysis or activated carbon precursors. These findings offer recommendations for large-scale extraction, including maximising CPH solid residue for bioenergy and activated carbon production, integrated into CPH biorefinery units.