Chill-filtration of whisky has been quite an issue, along with caramel colouring. But while E150a has to be declared on the label at least in a few countries like Denmark and Germany, we have to rely on the statements of the whisky producers when it comes to chill-filtration. One way to find out is the the “fridge test”. If the whisky turns cloudy, it is not chill-filtered. But there is another method that gives you more information about the whisky.
Have you ever noticed a coloured residue in your empty glass the next day? Sometimes, especially with cask strength whisky, there can be a rather thick layer of goo at the bottom of the glass. Now what could this be?
Here is an experiment I just did: I took two white saucers, filled the center with two different whiskies and let it evaporate overnight. The left saucer contained Mortlach 16 yo Flora & Fauna, the right one the new release of Bunnahabhain 12 yo. The choice was not random. I selected dark coloured, sherried whiskies because the results would be easier to see, I picked the Bunnahabhain because Burn Stewart decided to drop chill-filtration for their new releases, and I picked the Mortlach because I suspected it to be chill-filtered being bottled at 43% and offered by a company that has always relied on chill-filtration for their standard bottlings.
On the next morning approximately 90% of the whisky was evaporated. Both saucers had residue in them but they looked remarkably different.
The center of both saucers was covered by a brown layer, obviously from the dissolved components giving colour to the whisky that have started to precipitate. In addition to that, the Bunnahabhain saucer showed a distinctive very dark circular residue that was far less prominent in the Mortlach. The stronger residues at the outer rims of the center in both saucers are caused by the faster evaporation at the indentation. Sadly not visible on the photograph are the small patches of fat that were covering the remaining Bunnahabhain. These were not present with the Mortlach.
How to interpret the result?
Please keep in mind that this is not a proper scientific experiment. For this, the residues should at the very least have been weighed on a microgram scale and analysed with a microscope. But the visual differences already give strong clues.
1. Fat is Removed by Chill-Filtration
As could be expected, the Bunnahabhain remnant contained a visible amount of fat while the Mortlach didn’t.
2. The Amount of Fat Removed Is Not Very Large
The fatty patches on the Bunnahabhain were clearly visible, but the amount of fat seemed to be far less than 1% of the total liquid which itself was already concentrated by a factor of 10. I would suspect the amount of fat in raw whisky to be significantly less than 0.01%
3. Chill-Filtration Seems To Remove Not Only Fat
The dark rim of the Bunnahabhain saucer was an indication that it contained something which wasn’t present in the Mortlach to such an extent. This “something” evidently is subjected to a radial force during evaporation causing it to accumulate which strongly hints on microscopic solids that are dispersed in the unfiltered whisky. Chill-fitration works by turning fat into soild state so it can be removed with a filtering substance. Evidently this process will also remove substances that are solid at room temperature.
4. Chill-Filtration Seems To Remove More Solids Than Fat
Comparing the amount of fat on the almost totally evaporated Bunnahabhain with the dark rim remnants suggests that fats only make up a fraction of the total residue.
Before drawing any hasty conclusions it should be pointed out that the nature of the solids that can be found in unchill-fitered whisky remains unclear with this experiment. It is not certain at all that these solids have a noticeable effect on taste. The dark colour of the solid residue could hint for example on carbon dust from charred casks.
But even if an experiment like this can’t give you detailled information of what exactly is in your whisky, the viusal appearance looks convincing enough to tell chill-filtered whiskies apart from unfiltered ones.
Title image by lugarzen / flickr