The Glycerol/Water Mixture Is an Effective Deep Eutectic Solvent for the Extractions From Food Waste Matrixes

Abstract

Deep Eutectic Solvents (DESs) are a novel class of organic liquids that are becoming increasingly important in the literature for their green and catalytic properties and for their peculiar structural features. Because of these, they are finding fruitful applications in many different topics. One of the most explored one is their use as green effective extracting agents from food matrices and food waste matrices of valuable bioactive compounds, thanks to their affinity with aromatic and phenolic compounds. 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 curves. This approach is used with both liquid starting components for the first time to our knowledge. This DES was then tested 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 glycerol only components, 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 mixture at the eutectic point as a DES and opens for a novel approach in which the extract could be directly used without further purification procedures considering the food grade of the DES components.