Wednesday, 6 July 2016

Sulphites in Wine

Since the arrival of the term “Contains Sulphites” on (EU) wine labels in 2002, after the Americans introduced the idea in 1988, many people have wrongly assumed that this is the cause of hangovers after drinking wine. In fact less than 1% of the population have allergic reactions to sulphites and hangovers are usually caused by other factors, such as the dehydrating effect of alcohol or a possible allergy to histamines. Sulphites have been used in wine for centuries and some believe the Romans used them, but the first written evidence goes back to 1487.

Raw sulphur

Sulphur is a naturally occurring chemical element identified by the letter S and is the 13th most abundant element in the Earth’s crust. It has all sorts of industrial uses and is a vital nutrient for crops, animals and people. Sometimes known as brimstone in the past, it is a yellow crystalline substance which emits a horrible smell when burned, as anyone who has been near a volcano will know. It has a number of useful properties for the production of wine as it is a powerful antioxidant and inhibits yeast and microbial activity.

Dusting vines with sulphur

In the wine trade sulphur is used in more ways than one. In the vineyard vine leaves are dusted with powdered sulphur as a protection against the deadly fungus Oidium and Mildew is combated with Copper Sulphate, but it also has multiple uses in the winery. In the form of a powder tiny quantities of potassium metabisulphate are dusted onto the grapes on arrival to prevent oxidation and in the form of sulphur candles it is used to disinfect barrels for re-use. In the form of the gas sulphur dioxide (SO2) it is used to protect the wine from oxidation and acetification, eliminate unwanted yeast strains from the alcoholic fermentation, prevent malo-lactic fermentation and help with colour stability in the bottled wine. It is even used in the cleaning of equipment.

Sulphur dioxide gas

Few are aware that many food products contain far more sulphites than wine, for example dried fruit, canned vegetables, condiments, relishes, dried fish among very many others. Unlike wine labels however, food products (in Europe) get away with “E220” in the ingredients list, this being the European Union Permitted Food Additives List number for sulphur dioxide which is permitted in controlled quantities. If a wine contains 10 milligrams per litre (mg/l) or more, and the vast majority do, the words “Contains Sulphites” must appear on the label. Wine can naturally contain 10-20 mg/l of SO2 as the result of yeast fermentation and the maximum permitted concentration in Europe is 400 mg/l. Red wines need less SO2 than white wines as they have more polyphenols as antioxidants but sweet wines need more because of the binding power of sugar in the wine and the risk of re-fermentation in bottle. Many food products contain up to 15 times more sulphur than wine.

Sulphur candles emit a blue flame

Such a useful substance will be very hard to replace, but due to allergenic worries alternatives to sulphites have been sought for years. One is ascorbic acid (vitamin C), a powerful antioxidant, but it doesn’t mix easily with the wine and works better with a little SO2. Then there is the EU research project called "so2say" which is experimenting with combining two natural ingredients of wine which should reduce SO2 by 95%. In Spain researchers have come up with another possibility, Vineatrol, which is made from extracts of vine prunings high in polyphenols. Of course wine can be made without the addition of any sulphur, but these “natural wines”, which could already contain up to 20 mg/l sulphur, require considerable winemaking skills and acceptance by the consumer, who is used to bright clean wines, of a more oxidative style of wine - everything in this world is a trade-off. Sulphur is permitted in limited quantities in organic and biodynamic wines as it is a naturally occurring substance. 


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