Waiter, there’s a speck in my whisky

The good and bad of chillfiltration

As it appeared.

First published in Prestige Magazine (May 2012 edition).

My parents taught me that a discussion of religion and politics should best be avoided in polite society.  I decided instead to avoid polite society.  A note to posterity:  if I ever warrant quotation then please make this my defining quote.  There’s a lot to be said (literally) for a bit of impropriety and irreverence.  In whisky society – where things can get quite impolite after a few drams – the parts of politics and religion are often played by a red-rag-to-a-bull known as chillfiltration.   Prompted by Bunnahabhain’s recent launch of their unchillfiltered range I decided to wade into murky, or should I say hazy, waters to confront this messy beast of a topic and poke it with a stick.

What is chillfiltration?  Let’s start with the converse situation, in which whiskies are alternatingly termed unchillfiltered or non-chill filtered.  The industry seems to have shown standardisation the finger and chosen divergent grammatical paths, but whatever one’s predilection for prefixes, hyphens and contractions, the meaning is the same.  I’m going to opt for concision and use the former henceforth.   A whisky, when it comes out of its cask after maturation, is loaded with fatty acids and oily compounds (known in more scientific terms as congeners), from which it derives much of its flavour.  These congeners however also tend to bond together and precipitate (i.e. form a haze) when the whisky’s temperature and/or its level of alcohol are lowered.  This is an unchillfiltered whisky and it poses certain problems…at least for some.

To the uninformed a hazy whisky is aesthetically displeasing; and it gives the (misleading) impression that it might be decomposing.  The motivating reason for chillfiltration is to eliminate the occurrence of this hazing in whisky.  The process works like this:  the whisky is cooled to a temperature of around 0°C (give or take – some whiskies are more aggressively chillfiltered than others) and then passed through a mesh filter, thereby trapping and removing certain congeners.  The result is a clear, cosmetically attractive liquid.

To the informed whisky lover however chillfiltration is a double-edged sword: remove the congeners, remove the flavour.  It’s a somewhat ruthless solution.  There are other gentler ways to mitigate hazing; for instance an alcohol level of 46% ABV would guarantee solubility at room temperature, without any flavour removal required.  Unfortunately, if the temperature drops, and if ice or cold water is introduced, the hazing would reappear, so it’s at best an incomplete alternative.  Also, at 46% a whisky is circa 15% and 7% more expensive than at the statutory minimums of 40% and 43% respectively, hence affecting its commercial proposition.  Some brands have nonetheless followed this course in the quest to offer unchillfiltered whiskies, but they’re in the minority – primarily single malts for whom the flavour stakes are higher, and whose consumer base is likely to be more aware of such peculiarities.

Until recently I’d been part of the faction that poured scorn on chillfiltration.  It was, in my opinion, a creation of laziness and greed.  To be fair though it’s a bit of a prisoner’s dilemma – it doesn’t make sense to invest in education on the matter individually, so invariably the bulk of the industry has taken the path of least resistance, but, regardless, depriving us of optimal product in doing so.  Some producers claim that chillfiltration doesn’t affect the flavour in their whiskies, but the force of contrary logic and the self-interest inherent in these justifications would suggest otherwise.  Others yet claim that they chillfilter less aggressively, which still results in flavour still being extracted, just less of it than would otherwise be the case.  So it seems clear-cut then that chillfiltration does a disservice to the flavour-seeking, pukka whisky lover.  Maybe, maybe-not.

Conventional wisdom is all well and good, but evidence is the only way to discover what’s really true about anything.   There’s little publicly available data on chillfiltration but I recently came across some research by Matthew Ferguson-Stewart (a whisky aficionado) that poured fuel on the chillfiltration fire.   His experiment involved a blind tasting of unchillfiltered and chillfiltered versions of four whiskies by a small panel of experienced tasters.  The shocking conclusion: the tasters identified the difference but preferred the chillfiltered versions.

What should one make of this?  Perhaps the experiment was too limited.  Certainly it should be verified on a wider and larger scale.  Perhaps some congeners, in this case the balance of those removed, are somehow offensive.    For the moment though it has made a contentious subject even more inflammatory.  Given that the bulk of whiskies available to us are chillfiltered, I find his results encouraging.  We can’t draw any definitive conclusions yet, but there’s hope now that the typical whisky that we’re drinking isn’t in fact a diminished version of itself, as we had previously believed…and that can only be good news.  May the dram be with you!


4 responses to “Waiter, there’s a speck in my whisky

  1. Interesting post. Well done.

  2. Matthew Fergusson-Stewart

    Hi Patrick,

    Thanks for reading my article, I enjoyed yours above as well.

    Important to note that although our little group generally like the chill-filtered versions better, it’s worth noting that we did not conclude that chill-filtered is better. Four people with four different whiskies is the biggest experiment of this kind that I know of, but in scientific terms it is tiny. For me, the research was more exploratory than exhaustive. I’m looking forward to someone doing a bigger and better experiment!

    Thanks again,

    • Thanks for the comment Matt. I take your point entirely – we’re always under word count pressure in these printed articles so I may not have been explicit enough about it in the piece. I recently had an interesting chat with Ian MacMillan from Burn Stewart. He suggested that chill filtration can sometimes correct flaws in distillation. I can’t remember the whiskies which you used for the experiment and it’s not my intention to cast aspersions on these products, but this could be a potential explanation for the results. Keep me posted about version two – I’d love to hear all about it.

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