Preservation … versus the morning after 15 December 2005

Sulphur dioxide’s role in wine – expounded by Martin Moore

For centuries, in fact, since Roman times, winemakers at the end of a vintage have been burning sulphur strips in their clean, empty barrels to sterilise them for when they will be filled again with the wine of the next vintage. It was while following this age-old custom that I remembered promising some time ago to discuss the use of sulphur dioxide in the cellar. Such a discussion has now become more relevant as our new labels also state that the wine 'contains sulfites/sulphites', a requirement for all wines sold in the United States and the countries of the European Union.

Sulphur dioxide has the wonderful capacity of reacting with oxygen and so preventing oxidation with its undesirable effect on the colour and flavour of a wine. The Romans already discovered its remarkable preservative capabilities, and to this day it is an indispensable tool of all winemakers worldwide.

Sometime during the 20^th century the mystical 'they' discovered that apart from keeping wine containers safe for future use, sulphur dioxide protected wine not only against oxidation but also against a vast array of moulds, wild yeasts and bacteria.

I have come across quite a few negative perceptions about sulphur dioxide in wine, the most common being that it causes headaches and contributes to hangovers. Neither of these is based on fact. (I intend addressing the whole question of hangovers more fully in the January issue when readers might be more receptive to the message – although for some it will probably come too late!).

In a time as health-conscious as ours most preservatives are viewed with suspicion by consumers, even those that are natural substances like sulphur dioxide. Perhaps in the case of the latter, some of the negative perceptions were fostered by the tendency in years gone by of some winemakers to add large quantities of sulphur to the wine as a kind of cure-all. You can bet your bottom dollar any ill effects those wines might have had were caused by the wine itself and not the sulphur dioxide.

Over the years the legal maximum winemakers can add to wine has been reduced substantially. Because of the way wine is now made we in any case need so much less than in the past. By making wine in closed tanks instead of open cement vats there is, for instance, much less exposure to oxygen and therefore less need for sulphur dioxide.

Wines preventing colds and flu…

There are alternatives to sulphur dioxide, but not a single one that does the whole job. One could, for instance, use ascorbic acid to help prevent oxidation, but in wine we have to use it in conjunction with sulphur dioxide – it is not a substitute for the latter but complements it. (I notice some producers preserving their fruit juices with ascorbic acid claim these are 'vitamin C enriched'. That's about the same as winemakers using antibiotics to knock out possible bugs and then claiming those wines prevent colds and flu!)

There are also other chemical substances that are effective against specific organisms, but because of its multiple effects it is unlikely that a single substitute will be found for sulphur dioxide. So why use a concoction of ten or more chemicals to get the same result?

What also makes sulphur dioxide special is the fact that it is effective in small amounts and then mostly in free form (which means that in time it becomes bound to substances in the wine). We add small quantities during the whole winemaking process and end up with very low sulphur levels. We measure the pick-up of dissolved oxygen at every stage and pump in inert gas like dry ice (frozen carbon dioxide) to replace oxygen in pipes and tanks before using them. The secret is not to go according to the book, but for the winemaker to understand what he is doing and to use sulphur dioxide as sparingly as possible.

The simple truth is that it is impossible to produce wine that will last without using sulphur dioxide. Wines made without it, whether organic or not, should really carry a sell-by date because of their limited lifespan. It is only through the judicious use of sulphur dioxide that we can produce healthy wines that can be laid down with confidence, wines that will mature well and bring joy to the heart, joy that is not spoilt by any after-effects the next morning.