Precision Vinification Without Added Sulphur Dioxide: Real-Time Gas Monitoring Across Multiple Vintages

The reduction or elimination of sulphur dioxide (SO2) in winemaking represents a major technological and sustainability challenge due to the central antimicrobial and antioxidant roles of this additive. This study evaluated the technological feasibility and chemical stability of a no-added-SO2 vinification protocol applied under controlled winery conditions over four consecutive vintages, compared with a conventional sulphite-based protocol. The no-added-SO2 protocol integrated closed-circuit operations, controlled inert gas management, temperature-regulated fermentation, strict hygiene practices, the addition of grape seed extracts as alternative antioxidant agents, and real-time monitoring of CO2 production and O2 availability via a smart tank. Across all vintages, wines produced using the no-added-SO2 protocol showed regular alcoholic and malolactic fermentations and volatile acidity values consistently below the sensory perception threshold (1.2 g/L). Total SO2 levels ranged between 0.3 and 86 mg/L and free SO2 ranged between 0.4 and 16 mg/L, attributable exclusively to endogenous yeast production. Multivariate analysis confirmed that vintage was the dominant factor affecting most compositional parameters, particularly phenolic and anthocyanin profiles, whereas sulphur dioxide management represented a secondary but clearly identifiable source of variability. These findings indicate that sulphur dioxide-free vinification is technically feasible when supported by precise process control and continuous real-time monitoring. Rather than a universal replacement for conventional sulphite management, the no-added-SO2 protocol should be regarded as a complementary and technologically contingent tool for sustainable SO2 reduction within a precision oenology framework.