suffer the sulfur Print
Written by Nikitas Magel   

Winemaking Witchery Series, Part 1: Sulfur Dioxide
Essays on the use of Chemical Additives & Enhancements in Winemaking

match_croppedBack when I worked in a wineshop, occasionally a customer would come in, asking for sulfite-free wine.  It wouldn't happen frequently, but when it did, I have to admit that I found it very frustrating.  And that's because, quite simply…

There is no such thing as sulfite-free wine!

Nevertheless, I'd come to understand that there is a great deal of knowledge lacking among wine consumers, and I embraced that sort of request as a ripe opportunity to dispel the belief that sulfur dioxide is necessarily a bad thing in wine (only in excess is it potentially problematic).   In fact, the every existence of wine as we know it today hinges on the antioxidant properties of this additive.

Now, in order to fully understand the reason for using sulfur dioxide, it's important to recognize the role of oxygen in winemaking.  Chartered Chemist and Master of Wine, David Bird describes it as being very similar to the effects it has on living things in general:

"Oxygen… is somewhat ambivalent, in that it both supports and destroys life.  From the very early days of our education, we are taught that oxygen is the staff of life.  Oxygen enables fires to burn; oxygen enables our bodies to metabolize food and release energy.  Life as we know it could not exist with oxygen.  However, there is another side of the story, because oxygen is also the main element involved in degradation and ageing."{footnote}David Bird, Understanding Wine Technology (San Francisco: Wine Appreciation Guild, 2003), 24. {/footnote}

And as that applies to life in general, so it does to wine.  While oxygen plays a positive role in some aspects of the making {footnote}Look for my forthcoming essay on micro-oxygenation {/footnote}— and later, in the drinking — of wine, for the most part it is destructive, necessitating constant control.  In fact, the hallmark of modern winemaking — what has resulted in significantly bolstering the quality of wines worldwide just alone in the last few decades — is precisely the accomplishment of tight control over elements in the process that directly cause or indirectly contribute to the decay of wine.  Oxygen is among the most prevalent and powerful of those forces, and advances in its control collectively mark a milestone in winemaking history.  Before such advances, the traditional winemaker was unlikely aware of the dangers oxygen posed, and carried on without taken any precautions to prevent it's degrading effects:

"Grapes were pressed in the presence of air; the juice would have picked up plenty of oxygen on its way to the fermentation vessel, and the finished wine would have been moved several times during the clarification process, gathering oxygen at every opportunity."{footnote}David Bird, Understanding Wine Technology (San Francisco: Wine Appreciation Guild, 2003), 25.  {/footnote}

Fast forward to modern times; enter sulfur dioxide.  This molecule is the singlemost important and effective measure in controlling the oxidation of wine. It's vital to wine's production and without any trace of it, wine would have a shelf life numbered in hours.  In fact, the additive is widely used throughout the food and beverage industry, allowing us to enjoy a great deal of fruits and vegetables in ways that would be impossible without it.  And so — notwithstanding an exquisite sensitivity to it, experienced by a tiny fraction of one percent of the population — blanket demonization of this preservative is frankly ill-informed and myopic.  Wine as we know it, quite simply, would be impossible were it not for the three protective roles played by sulfur dioxide:

  • Antioxidant: it binds chemically with oxygen molecules, essentially neutralizing them.
  • Antiseptic: it kills bacteria in the wine, one which is acetobacterium that is directly responsible for turning wine into vinegar.  This antiseptic attack is actually two-pronged, because the oxygen needed by this aerobic bacteria is removed by the additive's antioxidant property.
  • Antioxidasic: it destroys enzymes that promote the oxidation process; these are the same enzymes that turn fruit brown when exposed to air.

Now, none of this is to say that the production of all wines must necessarily involve the addition of sulfur dioxide.  Some winemakers choose to go without it — although this still does not make for sulfite-free wine, since traces of sulfur dioxide are produced by yeasts during fermentation.  Nevertheless, the choice to abstain from adding it requires a great deal of vigilance on the part of the winemaker, to prevent oxygen from accessing the grape must (juice) or wine during every stage of the production process.  And that approach has its risks:

"Toward the end of the twentieth century it became fashionable to reduce levels of SO2 additions.  As we have seen, levels of sporadic bottle oxidation (particularly in white wines) and Brettanomyces (in red wines) rose in direct consequence.  There has been a reversal in practice [since]… Skillfully and rationally used, the effect of SO2 is beneficial, particularly in the case of wines intended for medium- to long-term cellaring."{footnote}James Halliday & Hugh Johnson, The Art & Science of Wine (London: Mitchell Beazley, 2006), 221.{/footnote}

But even in wines where the additive is used, great care is taken to control exposure to oxygen — especially among producers of high quality wine.  The reason is that sulfur dioxide should really be used as an adjunct to the conscientious control of oxygen and bacteria in the production process, not as a way to make up for sloppy winemaking.  After all, too much of a good thing is, well, bad.  In high doses, the additive is toxic. {footnote}There are cases wherein people have died eating fruit salad that had been carelessly overdosed with sulfur dioxide.{/footnote}  But while there's no cause for alarm, since the small, controlled amounts used in winemaking are well below those legally-defined toxic limits, it's not a panacea to carelessness.   Quality-minded producers practice judicious use of the additive. end