Earlier this year I was on the island of Vulcano, one of a flotilla of small land masses that poke up from the Tyrrhenian Sea off the northeast coast of Sicily. It’s the place that gave European languages the word volcano, and one of four of Italy’s active, above-ground volcanic centers is located here. The photo above is a view from its cone.
I didn’t climb its slopes, but I can tell you that the moment I set foot on the island I smelled the sulfur in the air. It isn’t the pleasantest sensation, but one of the reasons the up and coming Roman Republic was willing to go to war over control of the islands was because they could collect sulfur easily here. The element was a valuable one in the ancient world, in regular use as a general purpose fumigant and a key ingredient in medical balms and ointments.
It was known from early days that wine held in a barrel fumigated with a sulfur match would keep longer. But it wasn’t until the 19th century that we drew the curtain back on the yellow stuff’s special powers when Pasteur demonstrated its talent for killing the newly discovered creatures known as bacteria.
Today, sulfur is widely employed in winemaking in both in the vineyard and in the cellar. It’s a cheap and effective treatment against two scourges of viticulture, the powdery and downy mildews (organic rules permit its use). In the cellar, it has a host of applications, all aimed at either suppressing unwanted biological activity or as a prophylactic against oxidation. Grapes may be dusted with it at harvest. Finished wine may get a first dose (in the form of potassium metabisulfate – a compound that releases sulfur dioxide when dissolved in an aqueous, acid liquid) once it is safely tucked away in barrel and a second when it’s bottled.
SO2 is especially valued in the making of white wines that depend on very limpid hues and bright fruit for their market appeal, since it retards the processes that would otherwise result in browning and a diminution of fresh fruit flavors.
It all sounds peachy until you realize that for all its wonder-working properties, sulfur has a dark – some might even say diabolical — side.
It’s an easy matter for a thoughtless winemaker to overdo sulfur treatments, leaving the consumer with an acrid aroma of burned match in the glass. These effects are temporary, however. The biggest knock against sulfur – and one that seems to be of increasing concern among more knowledgeable wine drinkers — is the indiscriminate way it goes about the business of killing. Sulfur can’t distinguish between good microflora and bad, so that when applied in advance of fermentation it can decimate local yeast populations that are an important — some would say defining – factor in that elusive thing called terroir.
It was known from early days that wine held in a barrel fumigated with a sulfur match would keep longer.
I wrote about the role of yeasts as a vehicle for expressing the unique character of site a few weeks ago (To understand what distinguishes one wine from another, pay attention to the little things) so I won’t go over that ground again. It’s enough to say that once sulfur has been applied to unfermented juice in sufficient quantity it’s likely that of the many species of yeasts typically in play only sulfur-tolerant varieties will survive to complete fermentation and reproduce.
It’s easy to understand how by means of a classical Darwinian process a local population of feral yeasts can rather quickly evolve from something shaped by prevailing natural conditions into something largely determined by a single, dominating trait: a tolerance for high levels of sulfur.
Producers eager to avoid deforming the naturally-occuring conditions under which their wines develop can choose to forego applications of sulfur in advance of fermentation. This is the approach naturalist winemaker Frank Cornelissen described to me when I interviewed him in his Mt. Etna vineyards a few days after my visit to Vulcano. “Sulfur kills enemies, but allies too,” is how he put it.
In part because sulfur constitutes an “off-farm input,” a deep ambivalence – not to say hostility — toward the mineral has become one of the defining elements of the natural wine movement. For some, terroir can only be fully expressed in a sulfur-free environment.
Unsulfured and minimally-sulfured wines are less well protected against oxidative influences, however. As a result they may display less of the brilliant clarity and lively fruit flavors consumers have come to expect in modern, commercial wines. This is especially true of oxygen-sensitive whites.
This isn’t necessarily a negative since low-to no sulfur wines may offer a spectrum of flavors and aromas that are beyond the reach of their conventionally-made counterparts. With primary fruit in retreat, wines can show an earthier, more savory dimension and exhibit textures that are more loosely-woven and layered.
But then, unprotected wines can just go off — overwhelmed by bacteria that can make wine genuinely strange and give rise to what are hard to call anything but faults. Wine can smell awful, turn to vinegar. It’s hard to see how the interests of terroir are served by a wine that’s not appealing enough to drink.
The time may come when alternative solutions are found for the problems sulfur solves and remedies for the ones it creates (including the mysterious wine headache – a subject for another post). Until then, conscientious winemakers will just have to reconcile themselves to the uneasy, bipolar relationship it demands.
But isn’t that what frenemies are for?
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