A comparative study of sulfite quantification methods in wine

Abstract

Sulfites remain essential preservatives in winemaking due to their antioxidant, anti-oxidasic, and antimicrobial properties. The international Organization of Vine and Wine (OIV) defines maximum permitted levels through the OENO 09/1998 Resolution and requires sulfite labelling above 10 mg L^-1, a threshold associated with potential adverse effects in sensitive consumers.

In a context where reducing chemical inputs is a growing priority, a robust understanding of sulfite and accurate analytical tools become crucial. Currently, only two methods are officially recommended by the OIV: iodometric, so-called Ripper method, and aeration-oxidation, also known as Monier-Williams or Frantz-Paul method, while colorimetric, and FTIR based methods may also be used upon previous accurate calibration.

Beyond these approaches, numerous alternative methods have been proposed in the literature. However the question remains: is there a method capable of replacing the current ones? Ideally, such a method would be accurate, or even more accurate than existing techniques, while being simple to use, fast, cost-effective, and in line with the principles of green analytical chemistry. Moreover, the complexity of the wine matrix makes it difficult to fully understand how sulfites behave in wine. This highlights the need to develop alternative methods to better explain aspects of sulfite chemistry that are not yet understood.

This study provides a comprehensive overview of most of the analytical methods for sulfite quantification with a comparison based on their analytical performance and their compliance with green analytical chemistry. It includes the methods reported in the literature and the commercial instruments used by professionals. By combining a range of emerging technologies and methodological innovations, this work highlights the current opportunities to improve sulfite analysis and supports the development of more efficient approaches in the future.