Sulfur dioxide use in winemaking has been coming under the spotlight as a minimal-intervention movement agitates for less reliance on the compound. Sulfur has taken flak for causing health problems, although the scientific community is divided on the issue.
That prompted a Colorado State University study of consumer perceptions of sulfites and whether drinkers would pay more for a bottle labeled “low in sulfur.”
The findings, published by the American Association of Wine Economists, are that consumers would be willing to pay a little extra – about 64 cents – for wines that contain low levels of sulfites. In comparison, the premium placed on organic wine is $1.22 – nearly double – which suggests public awareness of the addition of sulfur is embryonic.
The researchers offer an alternative explanation. Consumers, in their view, are aware that “organic production protocol prohibits, among other things, the use of added sulfites.” In other words, if drinkers pay the extra for organic wine, low sulfites will be included in the package.
Sulfur dioxide (SO2) – in the form of potassium metabisulfite – is added to most wines and many other food products for its antimicrobial and antioxidant properties. The term “sulfites” on wine labels refers mainly to sulfur dioxide, but also includes sulfurous acid and other sulfites.
But sulfur dioxide is also a natural by-product of fermentation, so it is unlikely an SO2-free wine could ever be produced. Most yeast strains yield 10–20 milligrams per liter of SO2 during fermentation, although some, such as FX10 and M69, produce significantly more than others. Without sulfur, wine is prone to oxidation and spoilage.
Consumers have been asking questions about SO2 since wine labels started to carry a “contains sulfites” message. Sulfite mentions, after all, share label space with warnings that women should not drink during pregnancy, and against drinking and driving.
Although a small number of drinkers suffer ill effects from sulfites, sulfites in turn may be unfairly maligned. “Having a warning [on the label] facilitates the attribution of any negative experience to the sulfites,” says Marco Costanigro, an associate professor at Colorado State University, who co-authored the study.
“Consumers say, ‘If things go wrong, I’m going to blame it on the sulfites.’ If the label said ‘contains tyramine’ they might react in a different way.”
Drinkers blame sulfites for a range of health problems, including breathing difficulties, allergic symptoms and headaches, but the jury is still out on whether sulfur is actually the culprit. Histamines, which are produced by yeast and bacteria, and tyramine, an organic compound in red wine, have also been cited as possible causes.
Perception, though, is everything. The Colorado study found drinkers perceive sulfites to be the main cause of their self-induced headaches. Nearly two-thirds of the Colorado study’s sample who suffered headaches after moderate wine consumption believed sulfites were responsible.
The study also revealed that those who do get a headache after a glass or two of wine are willing to pay as much as $1.23 extra for a low-sulfite bottle. Those who don't generally have headaches are willing to pay 33 cents extra. Researchers worked hard to identify those who simply had a hangover, Costanigro says.
“Some people reported headaches from having a small amount of wine. The fact is that there are people who are reporting these negative effects from drinking wine and it’s not a hangover. I think there are those people — my wife is one of them.”
More than one-third of the study sample had experienced headaches from very little wine, which astonished the researchers. “We were surprised that the percentage of headaches was so high. This is just one sample, but the number was more than 30 percent and that’s a lot.”
Less surprising was the finding that the sulfite content of wines was not high on the list of considerations when it came to buying decisions. “If you see whether this would really matter in a person’s purchasing choice, we found that it didn’t,” says Costanigro.
“People would prefer a low-sulfite wine, but it’s not a purchasing priority.” Quality and price are the two most important factors for wine buyers in the United States, the researchers say.
What, though, is a low-sulfite wine? No legal definition exists, making “low sulfite” claims on any label hard to substantiate.
By law, at least in the United States and the European Union, bottles containing more than a meager 10 parts per million of sulfur dioxide must state they “contain sulfites.” The regulation has been in place in the United States since 1987, and in the E.U. since 2005.
In the E.U. the maximum total SO2 levels must not exceed 210 milligrams per liter in a dry white wine and 160 milligrams per liter in a red wine. The latter level is lower because the tannins in wine are a natural preservative, reducing the need for sulfites.
However, sulfur levels need to be higher in sweet wines because sulfur is eager to bind with the sugar. Once it is “bound,” it ceases to be useful as an antioxidant and antimicrobial, necessitating the use of added sulfites. In addition, sweet wines produced from grapes attacked by noble rot, or botrytis, contain the enzyme laccase, which promotes oxidation and browning of the wine, calling for even more SO2 protection.
It’s no wonder, then, that most wine producers are attached to sulfur dioxide. Not so, however, the natural wine brigade, which is having mixed success doing without added sulfur. Some, but not all, of these wines end up unintentionally fizzy, or bretty (metallic) — reeking of manure or sticking plaster.
Stellar Winery in South Africa's Olifants River has successfully commercialized a “no added sulfur” range, including an Organic Cabernet Sauvignon and a Shiraz, and claims to be the top-selling organic producer in the U.K. Whether the wine lasts in the bottle is another matter.
Acknowledging the no-sulfur-added wines’ somewhat mixed results, the Colorado report observes: “Consumers may be actively deterred from purchasing a low-sulfite wine if they perceive that quality may suffer.” When producers forgo the use of sulfites, “there can be a higher risk of oxidation and spoilage of the wine.”
Even so, the researchers conclude that a “no added sulfites” label could be a useful way of gaining consumers’ attention. The report’s authors suggest “offering a money-back guarantee would remove the barrier to making a purchase, but it would also shift the risk to the producer.”
In Costanigro’s view, no-sulfites wine will remain a niche category. They won't be piled high at a Costco near you any time soon.