Optimization of phenolic extraction from coffee by−product using response surface methodology and their antioxidant activities

Abstract

            Coffee is one of the most popular beverage and important agricultural commodities. During the processing of coffee bean by wet process, coffee pulp (CP) which is a fibrous mucilagenous material was removed as a waste and become an environmental problem. The coffee pulp contained high amount of phenolic compounds which exhibited a wide range of physiological properties. This study aimed to optimize the extraction of phenolic compounds from CP using response surface methodology (RSM) and determine their antioxidant. The independent factors included microwave power (X₁), concentration of ethanol in water (X₂) and solvent to raw material ratio (X₃). The optimal condition parameters predicted were microwave power of 540 watt, 41% ethanol in water and solvent to raw material ratio at 22:1 with corresponding phenolic content 0.653 mg GAE/mL. These parameters were validated with an experiment carried out under optimal condition. The obtained phenolic 0.661 ± 0.003 mg GAE/mL was comparable with the optimized condition, which indicated that the model was adequate to optimize extraction of phenolic from coffee by−products. The CP extract under optimum condition (10 mg/mL) showed good antioxidant activities in Ferric reducing power (4.38 ± 0.01 mg AAE/mL), DPPH radical scavenging (97.62 ± 0.26%), nitric oxide inhibition (90.41 ± 4.72%), and superoxide dismutase activity (85.73 ± 3.72%).