Green solvents as an alternative, sustainable practice for the recovery of phenolic compounds in grape pomace

The large amount of agro-industrial wastes, generated by massive agricultural production to respond to the gradual increase in global population, are recognized as one of major causes of the environmental pollution worldwide. For this reason, it is important to find sustainable strategies aimed on reusing these by-products, exploiting their potential as alternative sources of health beneficial bioactive molecules. In the first part of the project, Cabernet Sauvignon and Petit Verdot grape pomaces collected in 2023 were characterized and used to perform solid-liquid extractions employing, as liquid green extracting phases, the so-called Deep Eutectic Solvents (DESs) and hydroalcoholic solutions as reference. The chemical characterization performed with a newly developed HPLC-DAD method on both fresh and dried grape pomaces, provided the phenolic compounds’ profile. In all thirty-six samples analysed, up to eight out to thirteen phenolic compounds taken as standards (gallic acid, coumaric acid, syringic acid, caffeic acid, catechin, rutin, quercetin and kaempferol galactoside) were detected with a maximum concentration of a single analyte determined in a single sample of 0.49 μg/g (quercetin). Two different DESs were selected as the best ones for fresh and dried grape pomaces, and will be used for the further optimization experiments. Then, the DPPH radical photometric assay was chosen to determine the relative antioxidant activity of the extracts. The encouraging results displayed an activity up to 14.9 mM Gallic Acid Equivalents. New in vitro bioassays and food fortification experiments are now planned. Ultimately, the possible use of the extracts in feed supplementation will also be evaluated.