Antioxidant strategies and mechanisms of cider fermentation with ergothioneine- and glutathione-producing yeasts: an alternative to sulphur dioxide

This study investigated the feasibility of substituting SO 2 with ergothioneine- and glutathione-producing yeasts in cider fermentation. The results indicated that the Optiwhite+E91-8 group reduced dissolved oxygen by 61.36% and enhanced total flavonoids by 5.54%, achieving antioxidant capacity comparable to the SO 2 -treated controls. Furthermore, organic acid content increased by 30.50% compared to apple juice, accompanied by a richer ester profile, enhanced fruity aroma, and improved flavor quality without dimethylamine formation. Ergothioneine is more stable than glutathione in acidic environments and may synergize with glutathione via redox cycling, regenerating post-oxidation to inhibit phenolic oxidation and sustain fermentation stability through sustained oxygen consumption. These findings confirm that inoculation with antioxidant-producing strains can effectively replace SO 2 , providing both a theoretical and technical foundation for the development of sulfur-free cider that boasts enhanced antioxidant activity and superior sensory qualities. This approach not only advances sustainable winemaking practices but also addresses consumer preferences for natural preservative alternatives.