Oenological Tannins as Sulfur Dioxide Alternatives in White and Red Winemaking: Chemical, Sensory, and Health Implications

• Grape and oak tannins effectively replaced SO 2 in white and red wine production. • Tannin addition reduced the SO 2 requirement, ensured smooth fermentation, and lowered the volatile acidity. • Grape tannin addition to pre-alcoholic fermentation enhanced the aroma and reduced methionol in red wines. • Sensory analysis revealed no significant palate differences between the tannin and SO 2 treatments. • No negative effect of human health were found in the SO 2 replaced treatment. Sulfur dioxide (SO 2 ) has long been an effective additive in winemaking, yet its use raises health concerns for sensitive individuals. While oenological tannins are increasingly recognized for their color-stabilizing and antioxidant effects, their potential to replace SO₂ throughout the winemaking process and their broader impacts on wine quality and safety have not been systematically studied. In this work, we present the first comprehensive evaluation of grape and oak tannins as SO₂ alternatives at multiple stages of both white and red wine production. By adding specific doses of tannins before alcoholic fermentation (0.3 g/L), after alcoholic fermentation(0.4 g/L), and after malolactic fermentation (0.4 g/L), we assessed their effects on wine chemistry, sensory attributes, and health-related parameters. Our findings demonstrated that tannin addition effectively reduced the need for SO 2 , supported a smooth fermentation process, and significantly decreased the production of volatile acidity ( p < 0.05). Wines treated with tannins showed no significant differences in redox potential compared to those treated with SO 2 ( p > 0.05). Notably, the addition of grape tannins to pre-alcoholic fermentation in red wines significantly enhanced the aroma profile (ethyl esters and higher alcohols) and reduced the formation of methionol. Sensory analysis revealed no significant differences in palate attributes between the tannin and SO 2 -treated wines ( p > 0.05). Importantly, the concentration of methanol, a health-related byproduct, was not significantly affected by tannin treatment ( p > 0.05). Overall, these results highlighted the potential of oenological tannins as a viable alternative to SO 2 in winemaking. And it was the first time to establish the feasibility and benefits of using 0.3 g/L grape tannins as practical SO₂ substitutes, with pre-fermentation grape tannin addition emerging as the most promising strategy for further development.