Glutathione Preservation during Winemaking with Vitis Vinifera White Varieties: Example of Sauvignon blanc Grapes

Glutathione (GSH) is a natural tripeptide present in grapes and wines. Its antioxidant properties are particularly useful during winemaking with white varieties like Sauvignon blanc. We examined two winemaking techniques, skin contact and pressing under nitrogen, for their effect on the GSH concentration in the must and wine. GSH was originally reported in the skin (64%), but later investigations on berries showed that juice (51%) and skin (40%) were far greater reduced GSH reservoirs than pulp and seeds. Therefore, we studied the impact of skin contact and pressing on GSH concentrations in must. Climate effects greatly influenced GSH concentrations in mature grapes. Depending on grape quality, GSH increased during skin contact from 2 to 55% and its release occurred in the first hours of maceration. During pressing under nitrogen, must GSH concentrations increased, reaching 80 to 90 mg/L when low pressure was applied (<1 bar). After two months in barrels, these wines still contained more GSH. We demonstrated that if winemakers wish to produce wines with high GSH concentrations, skin contact and pressing under nitrogen are good techniques.