Valorisation of grape pomace as source of bioactive compounds in Deep Eutectic Solvents ready-to-use extracts

The constantly growing global population, predicted to reach up to 11 billion people by 2050, is gradually making agro-industrial waste a serious issue about its contribute to the global environmental pollution. In a recent paper, grape pomace has been found, through HPLC-DAD analysis, antioxidant and antimicrobial assays, to have a great potential about its sustainable re-use as source of polyphenols, which have a significant impact on human health. Starting from these promising findings, seventeen different red and white grape pomaces have been collected for this study from various parts of Apulia (Italy) with the aim to perform green solid-liquid extractions, by using the so-called Deep Eutectic Solvents (DESs). Fourteen selected phenolic compounds’ profile of all the extracts was obtained through chemical analysis performed by HPLC-DAD with a previously developed method. Then, two cultivars, namely Sangiovese and Merlot, which showed a higher phenolic compounds content, were extracted using Betaine/Lactic Acid (1:4 mol/mol + 40% H2O) and Choline Chloride/Ascorbic Acid (2:1 mol/mol + 40% H2O) DESs and were selected for further characterization by LC-ESI-TOF-MS. Sixty-two different phenolic compounds were detected, with extraction yields up to three times higher using Betaine/Lactic Acid compared to Choline Chloride/Ascorbic Acid DES. This trend was confirmed by agar diffusion antimicrobial assays, in which only Betaine/Lactic Acid-based DES extracts showed significant effects. Considering these findings, in vitro digestion was finally performed on these freeze-dried DES extracts obtaining preliminary results about composition and bioactivity in each studied phase. An application of these products as ready-to-use food and/or feed supplements will be discussed.