Revalorization of Coffea arabica agrowaste through the recovery of phenolic compounds using a green extraction process

Abstract

The high caffein and tannin content of coffee agrowaste makes it highly toxic and hinders its disposal and recycling. The usage of this byproduct persists as a challenge in the industrial landscape. Coffee agro-waste is a potential resource of polyphenols with antioxidant activity and application in the food and cosmetic trades. This study presents a green extractive process using pulsed electric field (PEF) and microwave assisted extraction (MAE) to recover polyphenols from coffee silverskin and pulp, posing lower processing times and the use of water as the only solvent. The performance of this process on the phenolic yield was assessed through the Folin-Ciocalteu assay and the DPPH radical scavenging activity test. The phenolic composition of the extracts was also determined through HPLC-MS and quantified through HPLC-DAD. When compared to treatment controls, PEF + MAE treated samples were found to have enhanced yields of total phenolic content and radical scavenging activity in all analyzed residues. The chromatographic studies reveal that caffeic acid is the main phenolic compound of the three analyzed by-products. The HPLC-DAD caffeic acid quantification validated that a combination of MAE + PEF treatment in yellow coffee pulp had the highest caffeic acid concentration of all studied treatments.