Selection of extracts recovered from pomace/marc of white and red varietal grapes based on the composition, molecular weight and structural characteristics of polysaccharides for their future potential use in winemaking

The recovery of polysaccharide extracts from grape pomace is of interest due to their ability to modify the technological and sensory properties of the wines. This study reports the selection of polysaccharide extracts recovered from grape pomace/marc varieties based on their composition, molecular weight and structural characteristics. The structural characteristics of the pectins (measured by proton nuclear magnetic resonance) and polysaccharide contents showed varietal differences among the extracts. Malvasía de Rioja and Turruntés extracts, which were distinguished by a higher content of non-pectic polysaccharides (231.35 and 226.53 mg/g extract, respectively) and the highest fraction of grape structural oligosaccharides (67.97 and 67.22%, respectively). Viura extracts showed the highest content of total pectic polysaccharides (486.19 mg/g extract), the highest pectic polarity (50.13% degree of esterification) and the most pronounced fraction of high molecular weight polysaccharides rich in arabinose and galactose (61.52%). The higher polarity pectin and percentage of medium molecular weight polysaccharides in the Viura extracts and the Garnacha tinta extracts, together with the high rhamnogalacturonans-II content, could give the Viura extracts a different behavior with respect to the wine tannins. The extracts with the highest polysaccharide purity were obtained from Viura, Maturana and Tempranillo tinto. The addition of the selected Turruntés and Malvasía de Rioja extracts to the wine is expected to increase the content of volatile compounds and modulate astringency. The addition of Viura extracts could prevent tannin aggregation. In future studies, the technological and sensory effects of the selected extracts will be verified when added to different wines.