Sulfites Chemistry in Wines: From Reference Quantification Methods to More Sustainable Innovative Approaches.

Sulfites are widely used as preservatives in winemaking due to their antioxidant, anti-enzymatic, and antimicrobial properties. However, dietary sulfites have been linked to adverse reactions in sensitive individuals, especially those with asthma. The International Organization of Vine and Wine (OIV) adopted the OENO 09/1998 Resolution, which sets maximum sulfite limits according to wine types. It also recommends labeling when sulfite concentration exceeds 10 mg L-1, the threshold above which adverse effects may occur in sensitive individuals. Current analytical methods for sulfite quantification in wine lack precision at low concentration levels (typically below 10 mg L-1). As an example, the official aeration-oxidation (AO) method, also known as the Monier-Williams method or the Frantz-Paul method, even presents an error margin of approximately 10 mg L-1, making the accurate determination of sulfites in wine a significant challenge. A comprehensive overview of the main analytical methods developed for sulfite quantification in wine is discussed, highlighting both those currently applied in the wine industry and more innovative approaches that have been explored primarily in the scientific literature. The review also includes a preliminary section on sulfite chemistry, which is essential for a better understanding of the behavior of corresponding compounds, including free and bound SO2 species, within the complex matrix of wine. The rise of new methods that are more accurate, rapid, easy-to-use, cost-effective, and environmentally friendly presents valuable opportunities to enhance and optimize current sulfite management practices in winemaking. However, further development, validation, and standardization are still required before these new methods can be implemented in practice and commercialized.