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Chill-Filtration Does Make A Difference – The Experiment

by Oliver Klimek on August 24, 2011

Here is an experiment that I have been carrying around in my mind for quite a while. And as it often happens in such cases, there comes someone who does something along the same lines before you go public. It’s about how chill-filtration actually effects the character of a whisky.

In fact I am not unhappy at all that Matthew Fergusson-Stewart recently published an e-pistle about the inside-outs of chill-filtration as foreign corespondent to the Malt Maniacs. This does save me from the task of having to explain what actually happens when whisky turns cloudy by dilution or chilling. Matthew also proposed the same experiment that I had been thinking of: chill-filtering your own whisky.

Have you ever wished to taste the same whisky in its original and chill-filtered state to see if there is a difference? Chill-filtration is actually very simple. You don’t need an industry scale chill-filtration machine to do this. The machine is only needed to do it quickly and in high volumes. All you need is a freezer, filter paper and a funnel.

I filled a sample bottle with the new Bunnahabhain 12 yo at 46.3% and put it in the freezer for a few hours so it went cloudy. A small funnel was lined with a round piece of coffee filter paper and placed in the neck of a second sample bottle. Then I slowly poured the chilled whisky into the funnel. It turned out to be a rather slow process, so I did the pouring in small portions and put the chilled sample back into the freezer while the whisky was dripping.

I did not use all of the sample because I wanted to compare the remainder to the freshly chill-filtered whisky. But first I put both bottles back into the freezer to find out if the filtration was successful.

The filter paper sadly could not be used as piece of evidence for removed solids as it had been soaked full of whisky during the process.

The picture comparing the two samples is not quite as clear as I would have wished because you immediately get condensation on the bottles caused by the low temperature. But I hope you can see that the right bottle containing the filtered whisky is indeed clearer than the control sample.

This simple manual filtration did not completely remove all solids that had turned the original sample cloudy, but the difference is not only present optically but also on nose and palate.

After the samples were back to room temperature I compared them head to head in two Glencairn glasses. The original whisky was noticeably richer on both nose and palate, and this did not change after some minutes of rest and the subsequent addition of a few drops of water. Of course they had not become all different whiskies, but the chill-filtered dram seemed a little less complex and more spirity.

I am well aware that the comparison was not a blind test and so you should not take this as a waterproof scientific experiment. But I did the best I could to validate my result by neutralizing my palate in between and switching the order of tasting. I would ‘quantify’ the difference between the two drams by 2 or 3 scoring points for this particular whisky.

What has been evident in theory for me has now shown not to be contradicted by reality, to use a soft wording that takes into account the non-scientific nature of the experiment. Chill-filtration does physically take away something from a whisky, and these substances may not be sensorially inert.

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