Sensing Free Sulfur Dioxide in Wine

Abstract

Sulfur dioxide (SO₂) is important in the winemaking process as it aids in preventing microbial growth and the oxidation of wine. These processes and others consume the SO₂ over time, resulting in wines with little SO₂ protection. Furthermore, SO₂ and sulfiting agents are known to be allergens to many individuals and for that reason their levels need to be monitored and regulated in final wine products. Many of the current techniques for monitoring SO₂ in wine require the SO₂ to be separated from the wine prior to analysis. This investigation demonstrates a technique capable of measuring free sulfite concentrations in low volume liquid samples in white wine. This approach adapts a known colorimetric reaction to a suspended core optical fiber sensing platform, and exploits the interaction between guided light located within the fiber voids and a mixture of the wine sample and a colorimetric analyte. We have shown that this technique enables measurements to be made without dilution of the wine samples, thus paving the way towards real time <em>in situ</em> wine monitoring.

Keywords

• sulfur dioxide
• potassium (sodium) metabisulfite
• wine
• microstructured optical fiber
• sensors
• wine sensing
• pararosaniline