VIA ETS Laboratories:
The increasing demand for white and rosé wines with fresh, fruity or floral characters has led to significant winemaking challenges:
Because the aroma compounds in these lighter wines, such as Sauvignon Blanc, are fragile, oxidation can quickly cause a loss of aroma and flavor.
Even wines like Riesling and barrel-aged Chardonnay have experienced premature or atypical aging as a result of oxidation.
The importance of glutathione
Glutathione, a natural tri-peptide found in grapes and wine, is a powerful antioxidant that protects white wines and rosés from oxidation and loss of aroma or flavor.
A low level of glutathione in grapes leads to lower levels in the juice, and early losses of aroma compounds.
Glutathione levels fluctuate during production, as the compound can be absorbed by yeast and then released after fermentation.
If final glutathione levels are low in young wines, they will experience faster loss of fresh varietal and fruity aromas, and poor aging potential.
Glutathione interacts with other juice and wine constituents such as SO2, wine phenolic compounds, ascorbic acid and copper. These interactions affect both glutathione concentration as well as total juice or wine antioxidant status.
Monitoring glutathione levels can be beneficial at all steps of the winemaking process to maximize white wine aroma and flavor, and prevent premature aging.
The glutathione content in grapes indicates their antioxidant potential, and can be influenced by a number of factors including soil nitrogen, vineyard practices, and grape maturity levels.
Analyzing changes in glutathione levels during production helps to pinpoint where in the process glutathione is being lost – often from contact with air or exposure to copper residues.
A testing program can also identify winemaking processes that boost glutathione release after fermentation, and increase levels in wines.
For more information about glutathione analysis, contact Eric Herve or Steve Price.
Sampling Note: Juice samples are very sensitive to oxidation and loss of glutathione. ETS has created sampling kits that we provide free of charge for glutathione analyses to ensure accurate results.