The Influence of Sulfur Dioxide Concentration on Antioxidant Activity, Total Polyphenols, Flavonoid Content and Individual Polyphenolic Compounds in White Wines during Storage

Wines represent a rich source of bioactive compounds, especially polyphenolic compounds, which mostly contribute to the antioxidant activity. Sulfur dioxide (SO₂) has mostly been used as a preservative in winemaking to prevent oxidation during storage. The aim of this paper is to evaluate the changes in SO₂ levels and the influence of sulfur dioxide addition at seven different concentrations on the antioxidant activity (detected by DPPH-2,2-diphenyl-1-picrylhydrazyl and the ABTS Trolox equivalent antioxidant capacity methods), total polyphenols, flavonoid content and individual polyphenolic compounds (determined by the HPLC high-performance liquid chromatography method) of white wines during 5 months of storage. The assayed sulfur dioxide concentrations show a decreasing tendency with time, with a final decrease of more than 50% in comparison with the start of the experiment. Between the first and second measurements, the average decrease in sulfur dioxide was 16%. In the following interval, it was found that the maximum decline in SO₂ was 26%. The changes in SO₂ levels cannot be considered statistically significant. At the same time, we observed a decreasing tendency in the TPC content during storage. The antioxidant activity determined by the DPPH method at the beginning of the experiment ranged from 116.75 up to 270.62 mg·L⁻¹, while the antioxidant activity increased with sulfur dioxide concentration. The AA detected by the ABTS method displayed a decreasing tendency during storage. In the case of the TFC content, we observed a significant influence of sulfur dioxide on the concentration. No addition or addition of high SO₂ concentrations negatively influenced the flavonoid content in the samples. During storage, we observed a highly variable content of phenolic compounds in relation to SO₂ addition. The most abundant compounds were chlorogenic acid, caffeic acid and epigallocatechin.