Chill Filtration: Science in Whisky

We had no idea what "chill filtration" was. So The Whiskey Library gave us a science lesson.

by The Whiskey Library


Chill filtration has been taking place within the whisky industry for many years, but recently many distilleries have begun to offer expressions that are clearly labeled as “Non-chill filtered”. This may seem like just another phrase meant to confuse the average whisky buyer, but to experienced whisky drinkers, this offers insight into the bottle’s contents and the care that the distillery or independent bottler has brought to the presentation of the whisky. Many people in the industry will tell you that chill filtration has no impact on the flavor of the whisky, while others will swear that it takes the integrity out of the spirit. Whichever side of the argument you fall on, or whether it makes any difference to you at all, we’re here to tell you a bit about what exactly it means.

Whisky in its natural state is full of fatty acids, proteins, and ester compounds that are invisible to the naked eye at higher alcohol strengths (ABVs). These compounds have aromas, flavors, and textures that are perceptible to experienced drinkers. When a whisky is cooled, or diluted to under 46% ABV, it will become cloudy because these compounds do not easily mix with water. When a sufficient percentage of ethanol is present, however, it prevents them from being visible. If a whisky is being bottled at barrel proof or at cask strength, this will be above 46% ABV the vast majority of the time. If this is the case, (or if a whisky is in a colored bottle, and the contents are not visible) a producer may not be concerned. However, the lion’s share of whiskies are bottled under 46% ABV, and for those, a distiller may be rightly concerned with a bottle’s appearance on the shelf.

For a whisky bottled at 40% or 43% in a clear bottle that has not been chill filtered, (or at the very least, simply filtered) the whisky will likely appear cloudy on the shelf, and not the pristine, golden liquid that the average consumer expects to see. To many, this may be a sign of degradation or of a whisky that has gone bad, when in actuality, it is simply whisky being whisky.

To prevent this misconception from happening, a distiller, after emptying the contents of a cask, will chill the whisky to just below freezing and run it through a series of filters, similar to the air filters in your home. Chilling the whisky causes those pesky fatty acids to clump up, making it easier for the filters to capture them as they pass through, thus eliminating the chance of a whisky appearing cloudy on the shelf or in your glass.

Whether a whisky is chill filtered or not is irrelevant if there is no effect on the experience for the consumer. Studies with professional whisky tasters and connoisseurs have shown that when tasted blind, it is difficult, if not impossible, to tell the difference. However, there is a large and growing contingent of vocal reviewers, critics, and consumers who will only buy single malt scotch bottles that specifically state that it has not been chill filtered. Producers and independent bottlers are responding with a growing number of non-chill filtered whiskies being offered in their portfolios. Next time you’re at the store, check to see whether your favorite bottle states that it is non-chill filtered. If it has not been chill filtered, add a few drops of water to your next dram, and watch it cloud up before your eyes; you may never look at whisky the same way again.

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