Semi continuous extraction/hydrolysis of spent coffee grounds with subcritical water
Abstract Spent coffee grounds (SCG) were treated with subcritical water (SBW) in a semi continuous reactor at different temperatures, pressures, and water flowrates. Yields of carbohydrates and phenolics reached 33.7 g and 4 g per 100 g dry SCG, respectively, at 200 oC, 70 bar and 10 mL/min. Liquors collected at the beginning of assays were richer in phenolics and poorer in carbohydrates, whose yield increased sharply when temperature reached 150 oC. Most carbohydrates were recovered as oligosaccharides, and practically all cellulose remained in the SCG recovered at the end of assays. Extracts exhibited DPPH antioxidant capacity and antibacterial activity against both Gram positive and Gram negative bacteria.
Journal of Industrial and Engineering Chemistry