Maximising Recovery of Bioactive Compounds from Coffee Pulp Waste Using Microwave-assisted Extraction

Coffee pulp is a major by-product generated from coffee bean production and is generally known as waste. This study employed response surface methodology (RSM) with Box Behnken Design (BBD) to determine the impact of extraction parameters and optimise the conditions for recovery of total phenolics, flavonoids, chlorogenic acid, and caffeine from coffee pulp using a commercial microwave-assisted extraction system (MAE) for further applications. The results showed that sample to solvent ratio and ethanol concentration significantly affected the recovery yields of bioactive compounds and antioxidant capacity. There were significant interactive effects between the radiation time and sample to solvent ratio, but no significant interactive impacts between radiation time and ethanol concentration, radiation time and power, sample to solvent ratio and power, and ethanol concentration and power on recovery of bioactive compounds and antioxidant capacity of the coffee pulp extract. The optimal conditions were found to be radiation time of 85 min, sample to solvent ratio of 1:100 g/100 ml, 42.5 % (v/v) aqueous ethanol solution, and machine power of 1000 W. Under these conditions, extraction yields of total phenolic compounds, flavonoids, chlorogenic acid, and caffeine were 38.68, 27.00, 6.95, and 5.47 (mg/g DW), respectively. The extract also had high antioxidant capacities, with values measured by ABTS, DPPH, and FRAP assays as 87.95, 9.3, 65.31 (mg TE/g DW), respectively. These conditions are recommended for the recovery of bioactive compounds from coffee pulp for further applications.