OPTIMIZATION STUDY FOR EXTRACTION OF THE VALUE-ADDED COMPOUNDS POLYPHENOLS FROM THE WASTE BIOMASS COFFEE SILVERSKIN IN THE PERSPECTIVE OF CIRCULAR ECONOMY

Coffee is one of the largest consumed drinks all over the world, generating a very significant amount of wastes during the beans processing. Among these by-products, coffee silverskin is a very interesting waste material, being a promising source of bioactive compounds, including valuable polyphenols as chlorogenic acids and caffeine. In order to valorize these valuable components, they should be isolated from the starting matrix through suitable processes, but the current conventional extraction procedures are not suitable. On the contrary, microwave-assisted extraction results particularly efficient, nowadays finding many applications in various fields. On this basis, the aim of the present research is the investigation and the optimization of the solid-liquid extraction of valuable antioxidant polyphenols from coffee silverskin under microwave irradiation. The influence of the main reaction parameters, such as temperature, extraction time and composition of the solvent, consisting of a green binary mixture of water/ethanol, has been assessed, also employing statistical modeling. Maximum yield in total polyphenols of about 45 mgGAE/g, expressed as mg of gallic acid equivalent for g of starting biomass, was experimentally achieved, a promising value, thus leading to an important step forward, in the perspective of improving this waste recycling in a circular economy perspective.