Valorization of grape stems

• An extract from grape stems was characterized.
• Antioxidant and antimicrobial activities of the extract resulted high.
• Odorant compounds found in the extract were similar to that found in wine.
• Grape stem extract is an economic and promising alternative to SO2 in winemaking.
• Grape stems are added-value byproducts.

The wine industry produces large amounts of grape stem byproducts, which have been described as a natural source of polyphenols. In the present study, an extract from grape stems was evaluated for its antioxidant and antimicrobial activities in model wine to determine its potential capacity to replace and/or reduce SO2 in winemaking. Additionally, its possible effects on aroma were studied.Grape stem extract (STE) showed high antioxidant activity and it can be proposed as an energetic antioxidant. Its antimicrobial activity was compared to that of SO2. STE showed a lower inhibitory effect than SO2 for Saccharomyces cerevisiae, Hanseniaspora uvarum, Dekkera bruxellensis and Pediococcus damnosus whereas STE seems to be more efficient against Candida stellata and Botryotinia fuckeliana. GC–olfactometry analysis of STE showed that its most important odorants are naturally present in wines, and thus olfactometric profile modifications in wine, after STE addition, could appear quantitatively but not qualitatively.It can be concluded that grape stems are compounds with a low sourcing cost, high antioxidant activity and good antimicrobial properties.