Sulfur, as sulfur dioxide (SO2), is the most important wine preservative and antioxidant, used in tiny amounts to protect against spoilage microbes and oxidation. Naturally produced in trace quantities by fermentation, it is also added at various stages. 'Contains sulfites' appears on most labels. Excess can give a harsh, matchstick smell; too little risks instability. Low- and no-sulfur wines are central to the natural-wine movement.
WHY IT MATTERS FOR COLLECTORS
Sulfur is not the headache culprit it is popularly blamed for, and it is largely what lets wine age safely. Low-sulfur natural wines need careful storage and prompt drinking, trading stability for purity.
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