Impact of Ascorbic Acid, Fumaric Acid, and Glutathione as Alternatives to SO2 on the Phenolic Composition of Red and White Wine

Sulfur dioxide (SO2) is widely used in winemaking for its antimicrobial and antioxidant properties. However, its intake is associated with adverse health effects such as headaches and respiratory issues in sensitive individuals, prompting the search for safer alternatives. This study evaluated the impact of ascorbic acid (ASC), fumaric acid (FUM), and glutathione (GSH) as potential substitutes for SO2 on the phenolic composition of red and white wines, providing mechanistic insights into their protective limitations. In red wines, ASC, FUM, and GSH resulted in lower concentrations of anthocyanins, flavonols, and hydroxycinnamic acids compared to the control. This reduction is attributed to insufficient microbiological control and oxidative side-reactions, such as the crossover effect in ASC treatments, where the lack of SO2 allows for the generation of hydrogen peroxide and subsequent pigment degradation. In white wines, FUM better preserved certain phenolic groups, whereas ASC and GSH resulted in reduced hydroxycinnamic acids. The findings indicate that ASC, FUM, and GSH did not fully replicate the antioxidant role of SO2, leading to phenolic compound losses. Among the tested alternatives, FUM demonstrated the greatest potential in white wines; however, FUM’s limited microbiological protection suggests it should be used with caution as a standalone preservative. These results provide novel insights into the role of ASC, FUM, and GSH as SO2 alternatives.