There’s a lot of talk these days about natural wine, organic, bio-dynamic. And there is no question that the people making these wines have brought the world back to basics after a generation of synthetic fertilizers and pesticides. But most of these same producers would be the first to tell you that grape-growing and wine-making would be impossible without recourse to some chemicals.
Copper sulfate, in the form of Bordeaux mixture, is used in the vineyard, sprayed repeatedly on the vines during the period of rapid growth to protect the tender new leaves and emerging grapes from fungal infections.
Sulfur, usually in the form of sulfur dioxides (SO₂), is used in the winery. Sulfur has been used since the earliest times to preserve food and as an antiseptic. In the wine-making process it acts also as an anti-oxidant and anaerobic agent.
It serves many purposes. Barrels are traditionally sterilized with sulfur smoke fumes. Small amounts of sulfur are added to the fruit as it comes in during harvest to neutralize any bacteria that may disrupt the coming fermentation. Sulfur is a natural bi-product of the fermentation process itself. Nature, it seems, looks after its own. SO₂ gaz, in imperceptible amounts, can be left in the wine when bottled to protect it (in the same way a small dose of sulfur might) and to give an added perception of freshness .
Good producers try to keep the levels of sulfur they use to a minimum. It is brimstone after all! And while there are some producers of ‘natural’ wine who make their wine without any additional sulfur at all, these wines can be very unstable. And that instability can easily lead to microbial problems which quickly turn wine to vinegar.
The opposite approach, too much sulfur, can be less immediately perceived. Sulfur can be used to stabilize wine. Producers who are shipping volumes of wine across an ocean are going to be tempted to make that wine as stable as possible. One way is by upping the sulfur dose.
I can’t tell you the number of times here in Burgundy that I have had people tell me that if they drank the same amount of wine at home that they drink here, they would have a headache in the morning. Is it a heavy dose of sulfur making you suffer? Our producers expect to sell their wines locally, rarely dreaming of it landing on another continent. So they keep their sulfur levels to a minimum. To us it makes sense than that small production wine that you drink in the region of production is less likely to give you that headache!
So we say be wary of too little sulfur, unless you know the producer and the wine has not traveled far. But wary too of too much sulfur, unless you like headaches.