Every now and again I’ll come across a Whisky that proudly declares “Non-chill-filtered”.
Up until a few years ago this meant very little to me. I would look at that label and think nothing of it, except perhaps a slight tinge of curiosity.
Now though I am going to dive head first in what exactly it means to be Non-chill-filtered and finally be able to put my knowledge into practice!
Non-chill-filtration obviously refers to the process of chill-filtration, or the lack thereof.
Chill-filtration is designed to remove esters and fatty acids from Whisky as these can cause hazes when stored at a low temperature. These compounds can also produce sediment in Whisky.
The process is done be reducing the temperature of the Whisky to around 0°C and straining it through a very fine filter.
This collects compounds called esters that create hazing in Whiskies of an ABV below 46% since they are soluble in alcohol. Unfortunately they are insoluble in water, so when the ABV is lowered by adding water, cloudiness appears.
Temperature is a key factor in the solubility of esters and as such chill-filtration is effective at removing them, but it also removes important flavour compounds.
So really the question of chill-filtration comes down to aesthetics vs. taste. Do you want your whisky to look good or taste better?
Esters have a slight effect on the flavour of Whisky, but it is the process of chill-filtration itself that removes these and other flavour compounds.
There is an argument in the Scotch world as to whether or not these compounds are actually essential to the flavour of Whisky but Bruichladdich is a distillery firmly on the Yes side.
The distillery claims thatthe presence of around 100 flavour compounds contributes to aroma, taste and mouth feel. These are also compounds that are regularly removed by chill-filtration.
For example, take ethyl acetate, an ester that contributes to aroma. This is created by the oxidisation of toacetaldehyde by ehtonol. It then becomes a fatty acid called acetic acid that in turn reacts to alcohol to become ethyl acetate.
This is one of the many esters and fatty acids that are removed during the process of chill-filtration.
You can see the dilemma. While aesthetically it may be desirable to remove esters to prevent hazing and sediment build up, it can also compromise complexity of taste.
There are many distilleries out there that believe chill-filtering has no effect on flavour.
But then there are also those who claim it has a major effect on flavour.
If you want to make up your own mind, the best possible solution is to grab a chill-filtered Whisky and a non-chill-filtered Whisky in the same category and the same price range, and compare the two for yourself!
I think this is the way forward for the chill-filtration debate, and we can always mark it up to scientific progress if anybody asks why we’re drinking two bottles of Scotch at the same time!