[here] Beer, Booze and Bars,
Issue: March 20, 2008
Title: Screw You, Sulphur
by Craig Pinhey
I’ve been involved in a several week long discussion online at the wineloverspage.com forum about the connection, imagined or actual, between screwcaps and sulphur defects in wine. Being a scientist originally (I’ve got moldy B.Sc. and M.A.Sc. diplomas to prove it), I can never take a wine defect at face, or is that nose, value.
Just saying a wine smells like sulphur is not good enough. Sulphur what? Sulphur dioxide? Elemental sulphur? Hydrogen sulphide? Disulphides? Ethyl or Methyl Mercaptans? Farts? There are many types of sulphur smells, of varying origins and chemical formulas.
Why does wine smell like sulphur sometimes?
Well, it’s hardly surprising, given that sulphur is used in various forms throughout the life…err…death of a grape as it proceeds from the vineyard to your glass. They use copper sulphate sprays in the vineyard to kill mold and prevent diseases. They burn sulphur sticks in barrels to kill bacteria and wild yeast. They add metabisulphite or inject SO2 gas into wine to prevent unwanted fermentation, to stop fermentations on purpose, and in bottling to preserve the wine, acting as an oxygen scavenger.
Sulphur, or as some folks call it, sulfur, is a key part of modern winemaking, like it or not. Some folks don’t like it, as a very small percentage is allergic. Some people want wines made without sulphur. This is difficult, but is being attempted by some winemakers. Some people, who want 100% organic wines from the vineyard to the glass, are eager to get sulphur completely out of the picture, but it’s not happening. Growers need it in the vineyard, and CuSO4 is a naturally occurring mineral, as is elemental sulphur, so they meet organic rules.
In the bottle, though, it may be possible to cut residual sulphur, although it is risky to make SO2-free wines. Refermentation could occur; the wine could become unstable and spoil or, worse, explode. But there has definitely been a movement towards lower SO2 in the bottled product. Certainly the winemaker does not want more than is needed for stability, because there is a smell threshold. Excess SO2 irritates your sinuses, and burns the back of your throat.
Why did I get into this? Well, I’ve encountered a rash (no, I’m not allergic) of screwcapped wines with sulphur in the nose lately. I’ve been buying a bunch of the sale wines at the ANBL, some of which are screwcapped New Zealand and South African Sauvignon Blancs, and I’ve noticed that every single one of them smells like a struck match. We also call this flinty. It’s a bit like I imagine hell will smell like. Brimstone. I know this smell already, actually, from my years in the steel industry, where we removed sulphur at super high temperatures, and even added pure sulphur sometimes. I know what burnt sulphur smells like.
We typically associate this flinty smell with either Sauvignon Blanc (a varietal trait, owing to a chemical called pyrazine) or excess SO2, but it gets more complicated than that. How could a 2004 Sauvignon Blanc still have excess SO2? Jeez, how much did they bottle it with? SO2 is normally associated with young whites, where the SO2 has not been incorporated into the wine yet through various reactions.
So, like any Sommelier worth his tastevin (Confession: I never use mine) I investigated online, and found a few interesting things.
There have been accusations of screwcapped wine having a higher than normal level of sulphur problems, mainly of the H2S variety. Hydrogen sulphide really stinks. Like rotten eggs or sewer gas, or maybe farts, lots of farts, working together to take you down. It is not supposed to exist in the final product, but can sometimes form during fermentation and aging processes. Other comments in the research noted burnt rubber, skunk, garlic and onion. All unacceptable in wine, unless you have the palate of my long deceased beagle, Jet (he’d want dead fish added to balance out the flavours).
Some have claimed that this is the cork lobby trying to out screwcaps as having their own problems, just as natural cork has the problem of TCA (”corked” wine, that smells like chlorine poured into a musty basement). I don’t think so.
Research shows that screwcapped wines go into a reductive state, as opposed to oxidative, because the cap creates a much tighter seal than for natural cork. When reductive, chemical reactions can happen that produce complex sulphur compounds. One of these (Ethyl Mercaptan, CH3CH2SH, to be specific) smells like a struck match. If the reaction proceeds far enough, you can get disulphides, things that smell like rubber and garlic, like this sucker: CH3CH2SSCH2CH3. I’ve smelled these things in old wines. These cannot be removed easily.
I’m still learning about sulphur, and I’m still trying those sale wines. The good thing about a little excess SO2 or a hint of H2S or mercaptan is that you can often get rid of it by agitating the wine by decanting it, or by putting your palm over your glass and shaking it vigorously, but it is still an inconvenience. And some wines don’t seem to lose the smell. Another trick is to put copper (a penny or wire) in the wine, which can react with sulphur and remove the irritant.
Some of these wines have been on the shelves a long while. Maybe time is no friend of the screwcap. Maybe the sulphur problem increases with time and temperature.
Either way, I’m convinced there is a link between screwcaps and sulphur, at least with certain wines, and I’ll be following this story to the end. My hope is that winemakers are still adjusting to the screwcap, and the sulphur problem should dissipate, and hopefully disappear. To “cap” this off, I’ll be cautious about buying screwcap wines if they are older than two years. Screwy, huh?
Craig Pinhey can smell sulphur. Could it be that my time is coming? Visit Craig at www.frogspad.ca.
