What actually is chill-filtration?Chill-filtration is the process of removing esters and fatty acids from Whisky. This is done as those elements cause haze when the liquid is stored at low temperatures, and they can also produce sediment.
To carry out chill-filtration, Whisky is reduced to around 0°C and strained through a very fine filter.
This collects esters, which create hazing in Whisky with an ABV below 46%. They are soluble in alcohol, but insoluble in water, so when the liquid is diluted, hazing can occur more easily.
How does chill-filtration affect the taste?Temperature is an important part of chill-filtration and therefore it does have an effect on taste. Esters themselves carry certain flavour compounds as well so removing them well inevitably change the taste.
As we can learn from Bruichladdich Distillery's "Guide to chill-filtration", there are around 100 flavour compounds that contribute to taste, aroma and mouth feel. These compounds are removed by chill-filtration.
An example of this is ethyl acetate, which effects the aroma of Whisky. It is created through the oxidisation of toacetaldehyde by ehtonol and becomes a fatty acid called acetic acid that in turn reacts to alcohol to become ethyl acetate.
It is also removed during chill-filtration, therefore having a direct effect on flavour.
Essentially, chill-filtration is carried out so hazing does not occur and sediment does not build up, rather than having any benefit on taste.
What are the benefits of chill-filtration?
It is for aesthetics rather than flavour, and as such, many distilleries have stopped carrying out the process, although most blended Scotch Whiskies are chill filtered for consistency in how they look around the world from batch to batch.
There are still some that argue that chill-filtration doesn’t affect flavour, but it certainly removes some of the complexity of the liquid.
The question to ask yourself when considering the debate is do aesthetics trump taste?
Do you like your Whisky for the look or for the flavour? It’s up to the consumer to make the ultimate choice, but with major distilleries and brands such as Ardbeg, Compass Box and Bruichladdich all getting behind the non-chill-filtered movement, it might not be long until the more single malt brands are getting involved.