Technical Yearbook 2023

MARCH

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The past, present and future of sulphur dioxide By Charl Theron

It is known that the main purpose of sulphur dioxide in winemaking is its microbiological control and protection against oxidation. This can be attributed to the so-called free sulphur dioxide, consisting of molecular SO 2 and the bisulphite ion (HSO3-). The pH of the wine determines the percentages of these two.

Sulphur dioxide measurements Early sulphur dioxide analysis started in the late 19th century. The so-called Ripper method was the first utilised by the wine industry. It is based on a colour titration method. This was followed in 1970 by the aeration oxidation method developed by Rankine. Methods utilising infrared spectroscopy and membrane separation followed, and consequently there were two sulphur dioxide analytical methods. The first was based on the direct oxidation of sulphur dioxide followed by immediate titration (Ripper). The second was the separation of the sulphur dioxide from the wine, followed by titration to quantify it (aspiration).

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TECHNICAL YEARBOOK 2023