Deep eutectic solvents-based extracts from grape pomace for the production of green alternative food and feed supplements

The large amount of discarded food and by-products in agro-industrial production is increasing and represents a serious issue to deal with for the impact on the global environmental equilibrium. A recent investigation assessed, through HPLC-DAD analysis along with antioxidant and antimicrobial assays, the richness of grape pomace extracts in polyphenols, a class of health beneficial plant-derived bioactive molecules. Subsequently, based on this study, seventeen different varieties of Apulian (Italy) grape pomaces have been collected and used to perform solid-liquid extractions with the so-called Deep Eutectic Solvents (DESs), an alternative green choice to the well-known conventional organic solvents. After a preliminary screening by HPLC-DAD, the quali-quantitative profile of fourteen polyphenols was evaluated with the previously developed method. The results obtained showed that Merlot and Sangiovese, extracted with Betaine/Lactic Acid 1:4 (mol/mol + 40% water) and Choline Chloride/Ascorbic Acid 2:1 (mol/mol + 40% water), were the best samples and were then characterized by LC-QTOF-MS to obtain the full metabolomic spectrum of bioactive molecules. Sixty-two polyphenols were identified assessing an extraction capacity up to three times higher for Betaine- based DES compared to Choline Chloride-based DES, as also seen by the antimicrobial assays, performed by agar diffusion test, in which this trend was confirmed. Based on these findings, Betaine/Lactic Acid freeze-dried extracts were subjected to in vitro digestion experiments: bioactivity and stability in each of the five simulated phases were evaluated. No synergistic effects and no improvements in the antioxidant activity and polyphenol content, were observed adding a probiotic to the samples with the extracts. Further in vivo studies on quails will deepen the use of these ready-to-use extracts in feeds.