The valorization of grape pomace from Montepulciano winemaking: A new source of functional ingredients for sustainable food industry.

The winemaking process generates huge amounts of waste every year. Fermented grape pomace, the major by-waste product, holds significant value due to its chemical composition and technological properties. In this study a multi-omics approach was employed for the detailed molecular characterization of fermented grape pomace from Montepulciano grape, a widely used Italian red grape variety. Grape pomace samples, including both seeds and skins, were analyzed after 0, 6 and 9 days fermentation time. Anthocyanins and flavonols were the predominant polyphenols in the skin fraction, which resulted stable to the pomace drying process. In vitro gastrointestinal digestion analysis using the validated Infogest protocol showed a 60 % increased bioaccessibility of these compounds. Proteomics and lipidomics of the seed fraction underscored its richness in protein/peptides and lipid suggesting potential technological and functional bioactivity. Although no significant difference was observed in the seed protein fraction between intermediate (6 days) and final (9 days) fermentation time, this latter exhibited a higher number of potentially bioactive peptides compared to the former. Additionally, glycomic analysis of grape pomace uncovered novel oligosaccharides which may represent high-value ingredients for the food industry. This multi-analytical approach indicated that incorporating grape pomace and/or its fractions into food production could support the dietary transition towards sustainable and healthy nutrition.