Grapevine & Wine 07/11/2011

Reducing sulphites is a scientific matter. Eliminating them is impossible

Sulphites hurt. Although they have been used since the ancient times, today it is mandatory to reduce their doses. It is necessary to discover alternative methods to control the wine micro-flora and to improve wine preservation

Sulphites hurt. There is no doubt about it, even the World Health Organization has indicated in 0.7 mg of SO2 the maximum daily dose per kg of body weight. This has prompted wine makers to report the present of sulphites on labels.

Sulphites destroy tiamin and cyanocobalamin (all B vitamins), complicate the functioning of our detoxificating system, can produce allergic reactions and interact with cortisone based drugs.

This said, it is important to remember that sulphites have been used since the antiquity (for example, they were used by the Romans) as an antiseptic and antioxidant in food, including wine.

Wine is particularly interested by the issue, since it is one of the food and beverages where sulphites are more abundantly present.
Dried fruit (raisins, apricots, figs and plums) contain up to ten times more sulphites than wine, i.e. up to 2000 mg/kg, while wine can contain up to 210 mg/l. Fruit concentrates and other mixes (for example, for mashed potatoes) have a sulphit limit similar to wine.

To bash the use of sulphites with wine is at least bizarre and hypocritical, since several other types of food do contain them; however, it is useful to think of how to reduce them.

First of all, to do it, it is necessary to understand their function. Sulphite actions are:
- antiseptic on the micro flora of grapes and wine
- anti oxidant against pre-fermentation oxidations and wine oxidations
- solubilization of coloring substances
- fining

As regards the last two actions, several tools, additives and practices are now available in enology that are able to solubilize coloring substance and to clarify and fine.

The antiseptic and antioxidant functions are far more complex.
Many wine growers use different anti-oxidative products to protect wine, including natural ones which have been recently tested, such as oak tannins, ellagic tannins obtained from grape skin, proanthocyanidins from grapestones and even ascorbic acid. Results have been encouraging but not comparable to sulfurous anhydride.

As regards the antiseptic action, no commercial solution is able to reduce the microbial load and natural micro flora from grape skin, which may create problems during fermentation. According to Prof. Torriani, from University of Verona, a simple washing with water does not bring significant improvements. Some technique is being rested in different countries. For example, a recent research from University of Western Australia proposes to solve the problem in the mid to long term by means of UVB rays or ozone fumigation. The better option, as to now, is to use very healthy grapes, in order to reduce the risk of contaminations with bacteria or yeast, which can alter the fermentation balance.

Will it ever be possible to obtain a sulphite free wine in the future?
The answer to this question is no because it has been demonstrated that yeast naturally produces sulphites (10 to 30 mg/l) during fermentation. According to the bill of the Italian Republic n-. 114/2006, which modified bill n. 109/92, the threshold decided by regulators (10 mg/l or 10 mg/kg) impose to report that the wine “contains sulphites” on the label.

di Graziano Alderighi