OXYGEN INTAKE AND COLOR EVOLUTION IN SAUVIGNON BLANC AND MUSCAT OTTONEL WINES TREATED WITH ASCORBIC ACID AND GLUTATHIONE

Abstract

Understanding of antioxidants role in the wine matrix is an important aspect when it comes to sensory quality and conformity of the product. This study aims to compare the effects of sulphur dioxide (SO2) as a conventional antioxidant, alone or in combination with ascorbic acid (AA), in the presence or not of reduced glutathione (GSH) in white wines from Sauvignon blanc and Muscat Ottonel grape varieties. The results demonstrate that consumption of oxygen occurs differently, mostly according to the phenolic composition of the variety rather than the antioxidants added fortheir protection. Sauvignon blanc wines are believed, and our results proved it, to be more sensitive to chemical oxidation due to certain polyphenols that may act as a good substrate for oxidation. On the other hand, Muscat Ottonel wines seem to have more resistant polyphenols to oxidation, while the additional presence of higher concentrations of terpenes may improve this resistance due to their ability to act as antioxidant substances as well. Regarding color intensity values, which are desirable to be low in white wines, we observed that the smallest values were achieved in wine samples treated with sulphur dioxide with or without glutathione addition. Conversely, wines treated with ascorbic acid had the most intense color, due to the oxidation of polyphenols, irrespective of grape variety. The samples treated with combinations of sulphur dioxide, glutathione and ascorbic acid showed increased color intensity as compared to samples treated only with glutathione, but not to the same extent as in the case of samples treated with ascorbic acid alone. Knowing that the main tool of the winemaker for the protection of aroma compounds and polyphenols remains the use of antioxidant supplementation, a better choice was proven to be the addition of glutathione in the presence of a moderate concentration of SO2. Precautions should be taken when using ascorbic acid as antioxidant, because the depletion of SO2 is fast, and then ascorbic acid acts as pro-oxidant, releasing hydrogen peroxide.