The glycerol/water mixture is an effective Deep Eutectic Solvent for the extractions from food waste matrixes

Deep Eutectic Solvents (DESs) are a novel class of liquid systems that are becoming increasingly important in the literature for their green and environmentally friendly features, for their catalytic properties and for their structural features. In this work, the mixture glycerol/water at 1/2.55 molar ratio is demonstrated to be a DES thanks to the comparison of the experimental melting points with the theoretical melting curves. This DES was used as extracting agent on different food waste matrixes: onion, tomato and apple peels; spent coffee grounds and grape pomace. The results were compared with those obtained with the water and with the glycerol, showing a superior capability of the DES in the extractions, as well as superior antioxidant properties of the extracts. This promotes the use of this DES at the eutectic point and promotes a novel approach about the direct use of the extracts without further purification procedures considering the food grade of the DES components.