Revalorization of coffee by-products. Prebiotic, antimicrobial and antioxidant properties

Coffee industries are a key sector in the global economy due to income reporting and job creation. Coffee companies produce annually more than 2 billion tons of by-products such as coffee spent grounds (CSG) and coffee silverskin (CS). And most of which are thrown away and are not recycled for other purposes. Here we show the prebiotic, antimicrobial and antioxidant capacity of CSG and CS, as well as those melanoidins (a coffee component generated during the roasting process) obtained from the former. The prebiotic activity was important in both CSG and CS, although the presence of coffee melanoidins (CM) interfered with such beneficial properties. On the contrary, CM exerted an intense antimicrobial activity that could be used to avoid the growth of pathogenic bacteria in food products. In addition, CSG, CS and CM were highly antioxidant, even their indigestible fraction, which were the most relevant. Finally, we found that the addition of sugar during coffee roasting, namely torrefacto, increased the antioxidant and antimicrobial activity due to a larger generation of CM, although prebiotic activity was not affected. Therefore, CSG, CS and CM should be recycled in order to be used as a source of new food ingredients.