Metrolab Blog

THERMO Scientific | Fast and accurate automated method for free sulfite analysis in wine

Sulfur dioxide (SO2) is added to control the process of wine making. It serves many useful functions, for example, it acts as an enzyme inhibitor in musts preventing juice from browning. As a microbiological control agent, SO2 is added to the winemaking process to prevent oxidation in the finished product.
Sulfur dioxide can be found in wine in its free forms, SO2 (gas) and bisulfate ion (HSO3), or bound to compounds that incorporate a carbonyl group, such as acetaldehyde. Free forms of SO2 are pH and temperature dependent and because of the acidic nature of wines, SO2 is usually present and measured as bisulfate ion (HSO3). Results are reported as SO2.
The presence of total SO2, both free and bound, is regulated and, as a result, a warning statement is required on wine labels because sulfite is considered an allergen. The European Union established a maximum permitted level of total SO2 in wine varying from 150 to 500 mg/L which is dependent upon the sugar level of the product.
In the USA, the maximum level of total SO2 permitted is 350 mg/L. The measurement of both total and free SO2 can be automated using Thermo Scientific™ system reagents and Thermo Scientific™ Gallery™ discrete analyzers.
The goal of this study is to develop a method for free sulfite analysis in wine using automated discrete photometry.

Read complete application note.