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Sulphur in Whisky – Spice or Poison?

by Oliver Klimek on November 25, 2010

Time to take on another hot topic which seems to be the worst nightmare of many maltheads – sulphur.

How Does Sulphur Get Into the Whisky?

Notes of sulphur, often identified by descriptors like “flint, “burning matches”, or “firerackers” can sometimes be found in whiskies that were matured or finished in sherry or other wine casks. But how does it get there?

On first thought you might have the idea that it has somthing to do with the fact that most wines are treated with sulphur dioxide as antioxidant. But the sulphur notes in wine are not nearly as prominent as they can be in whisky, also keeping in mind that only a few litres of wine are left in the cask wood to be further “diluted” with whisky.

No, there is a different reason. Many sherry and wine producers burn a sulphur candle in the cask for sterilization to prevent the growth of bacteria. There can be an awful lot of sulphur in the smoke that settles down on the inner surface of the cask. Whisky filled into such a cask will pick up the sulphur immediately, so that even a short finishing period may result in strong sulphur notes.

Sometimes sulphur infuence can already be present in the newmake. But these notes are usually more on the “meaty” end of the taste spectrum, like in Mortlach. It is said that prolonged contact with the copper of the still during distillation reduceds the amount of sulphur in the spirit because of catalytic reactions. And if you look at some spirit safes in distilleries you will see blue copper sulfate crystals that prove this effect.

How to Cope With Sulphur?

Many whisky lovers are very sensitive to sulphur, some to an extent that they utterly detest malts that show only the slightest trace of it, Jim Murray being a prominent example. But there is also a small minority who can take quite a bit of sulphur and who may even appreciate those special aromas.

I admit that I belong to the latter group of people. Although there have been sulphured drams I wasn’t particularly fond of, I have immensely enjoyed heavily sherried whiskies that many others regarded as sulphur-infested. A prime example is a Duncan Taylor Glenesk 1981/2007 (Cask B933) that I had tasted before I started writing tasting notes. This bottle was particularly popular in Germany, and I have heard on various occasions that for some strange reason German whisky lovers tend to like sulphur more than others, myself being no exception.

A Suprising Parallel

Obviously, sulphur isn’t something that belongs in whisky in the first place. but if you think about it, there is another chemical component that can give whisky a very specific taste: the phenols from peat smoke.

Just like sulphur, peat wasn’t meant to be a flavouring agent for whisky. It was just the fuel used to fire the kilns to dry the malt. It turned out that many people found peated whisky to their liking, so nowadays peated whisky is made on purpose even though there is no necessity to use peat anymore in malting.

And just like sulphur, peat is not everybody’s favourite. There are quite a few whisky lovers who dislike peat, albeit the fraction will be smaller than those who dislike sulphur.

Why Not Mark Sulphured Whisky?

As of today, the occurence of sulphur in whisky is erratic. It may or may not be present, and it may even be different with varying batches of the same expression. Wouldn’t it be a nice idea for distilleries to take a little more care about sulphur?

Collect the sulphured casks to create sulphur spiced expressions for those who dig them, in the same time preventing those casks to end up tainting batches of standard expressions. This way you could serve both the sulphur lovers and the sulphur haters.

Photo by Matt Biddulph via Flickr

Matt Biddulph

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{ 4 comments… read them below or add one }

Aaron January 5, 2012 at 7:22 pm

The question of why sulfured whisky is not marked is a good one. To my tastes, sulphur is a poison. I have several that I am physcially unable to drink as the scent/flavor causes me to gag. The first time I experienced it was a Benriach 12yr bottled in 1994 (Oloroso Sherry matured), and the result was terrible. I couldn’t even think about Scotch for months without a physical reaction. I have had several peated/unpeated The Benriach that I have loved, but no longer trust them enough to try another.

Being so sensitive to it, I have a policy to never again buy from a brand of Whisky that I’ve found to contain sulphur. That means you, The Benriach and Glenmorangie (the Lansanta). I’m afraid that list will continue to grow, and it saddens me.

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bifter September 11, 2013 at 10:07 am

I know this article was written a while ago but it’s a contemporary topic. Just to nitpick a little:

Oliver, you identify Duncan Taylor Glenesk 1981/2007 (Cask B933) as a sulphured cask. Jim Murray identifies the 90s as the era that the sherry industry started using sulphur candles to sterilise casks (as opposed to the other uses they have in the industry) – he claims this was due to changed regulations stipulating that bottling should occur in Jerez rather than casks being shipped out for bottling at the point of destination. Consequently, if the casks were not sterilised they spoiled in the Spanish heat. 1981 would pre-date this, unless it was the case that this release was simply finished in a sherry cask? From the facts at hand there is perhaps some dubiety about how the sulphur arrived in this particular bottling.

The peat argument, i.e. that sulphur is just another unintended influence upon whisky, like peat, isn’t a good analogy for me. There are certain flavours that are generally considered desirable, sulphur is not one of those flavours. A smoky influence, however, is, e.g. smoked cheese, smoked bacon, etc. Another analogy might be that smoked fish are very popular however some fish, such as skate, can develop an ammonia reek when they get a past their best. No one would consider eating it, likewise if some process introduced an ammonia influence upon whisky it would most certainly be reviled. Producers don’t market ‘sulphured’ whisky because they know it’s unpopular and they never allude to sulphur in their tasting notes (aniseed, barbecued pork, even matchboxes, anything but ‘sulphur’). In my estimation it is an influence that should be rooted out at source.

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Oliver Klimek September 11, 2013 at 11:53 am

I would not consider Jim Murray to be the definitive authority on the use of sulphur candles in Spain. The 1990s may be the time when he first noticed it, as described in his 2013 “Bible”. But does this prove that sulphur has not been used before?

I am not the only one to have noticed sulphur in these old Glenesks:

http://www.whiskynotes.be/2010/glenesk/glenesk-1983-duncan-taylor-4931/

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bifter September 23, 2013 at 11:37 pm

Thanks Oliver. As you say, brimstone candles may well have been used earlier than Mr Murray claims. This is the first time I’ve heard of a bottling this age that suffers from sulphur and a bit alarming as I’ve normally considered 20+ years sherry casked bottlings as safe territory!

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