wine making

Why is testing for free sulphite – SO2 important in winemaking?


Sulphur dioxide or SO2 is a compound commonly found in wine. Sulphur can be added to the wine at various stages of fermentation to protect from effects such as oxygen exposure although this is often in small amounts. All wines contain sulphur dioxide collectively known as sulphites. However, due to the unique nature of each individual wine, those running the fermentation and quality process cannot simply add a generic or standard amount of SO2. The levels added are affected by the amount of SO2 that become bound to compounds in the wine, and this in turn is determined by the pH levels. The sulphur dioxide ions that are not chemically bound to other chemicals in solution and thus are free to react with substances are known as Free SO2.


Measuring sulphites in wine is important as too much sulphur in the wine can cause danger to health if drank excessively. If levels exceed 10mg/L producers must include a statement on the label, as sulphites can aggravate allergies and intolerance’s. Wine exporters must also bear in mind variations in national regulatory thresholds.


Randox Food Diagnostics offer multiple tests for wine analysis including free sulphite on both the RX misano and the RX monaco.


Free sulphite (free SO2)


Method No. of Tests Catalogue No. Sensitivity Linearity
Manual 100 FH10040 N/A N/A
RX misano 125 FH10040 3.10 mg/dl 81.32 mg/dl
RX monaco N/A FH10040 On request On request


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