Valorization of dry coffee grounds (DCG) and their oily extract: Coffea arabica and Coffea canephora and their mixture

Abstract

The coffee grounds CG are considered as a solid residue generated by consumers of ground coffee.For this purpose, three samples of dry coffee grounds DCG and its oily extract (Sample 1: Arabica, Sample 2: Robusta, Sample 3: mixture of two varieties) were subjected to a physicochemical characterization, quantification of primary and secondary metabolites and the mineral salts determination.The results show that the DCG of the three samples is a good source of carbohydrates with a max of 65.31±0.67%. In fact, the oil DCG extraction provided a yield with a maximum of 15.01±0.9%. The obtained values for the different physicochemical quality indices (refractive index RI , acidity index AI , ester index EI , saponification index SI and peroxide index PI),showed the conformity of the studied oils to the standards. Laquantification of secondary metabolites showed that the oily extract of mixture of two varieties is the richest in polyphenols with a value of 50.28±13.32 mg GAE/gr, on the other hand, the Robusta variety was found to be the richest in flavonoids (337.12±22.66 mg CE/gr).