Strategies To Reduce Sulfur Dioxide in Tannat Winemaking: Effects of Chitosan and Lysozyme on Microbial Stability, Composition, and Sensory Profile

Sulfites are the most extensively used additive in oenology to prevent oxidation and microbiological spoilage. However, their potential adverse health effects have increased the demand for low sulfite wines. Strategies are required to ensure microbiological stability while preserving the quality of the wine. This study evaluated strategies for reducing or replacing added sulfites using chitosan and low doses of lysozyme in Tannat winemaking, measuring their effects on microbial diversity, physicochemical parameters, and sensory attributes. Treatments were vinified by triplicate: reduced sulfites (RS: 30 mg/L), chitosan (C: 100 mg/L), reduced sulfites with chitosan (RS+C: 30 mg/L + 100 mg/L), reduced sulfites with lysozyme (RS+L: 30 mg/L + 5 mg/L), and a tra-ditional winemaking (TW: 125 mg/L sulfites). Sulfur dioxide lowered lactic acid bacteria counts, whereas chitosan and lysozyme treatments maintained higher populations. Metagenomic analyses showed decreased bacterial diversity under sulfur dioxide, while chitosan promoted a more complex microbiota. Lysozyme selectively reduced lactic acid bacteria, mainly affecting Oenococcus spp. Lower sulfite decreased phenolic concentra-tions possible due to reduced protection against oxidation, leading to color differences among treatments. The results indicate that strategies to reduce or replace sulfites in-fluence microbial dynamics, acidity, phenolic structure, and color, highlighting the importance of careful process management to maintain wine quality. Keywords: reduced sulfur dioxide, wine microbial community, Tannat wine composition.