Investigating the role of solvent type and microwave selective heating on the extraction of phenolic compounds from cacao (Theobroma cacao L.) pod husk

Abstract

Cacao pod husk (CPH) is a primary waste in the cacao industry that contains favourable natural antioxidants based on phenolic compounds. This study reported an investigation of the effect of extraction parameters to maximise the bioactive yields of CPH extract. The preliminary extraction was focused on high total phenolic content and continued to maximise the total monomeric anthocyanin and antioxidant activity that have the potential to be applied as food additives. The solvent selection and particle size were the key parameters for extraction to reach the maximum phenolic yield (100.4 ± 0.5 mg GAE/g dw). It was confirmed that 50% (v/v) aqueous ethanol was the most appropriate solvent, either based on experimental results or Hansen Solubility parameter prediction. At the same time, the comparison of microwave and conventional heating suggested that Microwave-assisted Extraction was the best method to get high phenolic content due to its selective heating effects. The results showed that the maximum bioactive yields were 0.37 ± 0.0 mg Cy3GE/g dw of anthocyanin and 3.36 ± 0.02 mg TE/g dw of antioxidants obtained under 50 °C and 5 min extraction time. Gallic acid, catechin, epicatechin, coumaric acid and quercetin were identified in CPH extract using High-Performance Liquid Chromatography.