Have you picked up a bottle of whisky recently and seen the statement “non-chill filtered” blazed across the front? Maybe you’ve just heard a bartender, a whisky drinking buddy or a magazine mention chill filtration. Or perhaps you’ve never heard of it but now I’ve piqued your interest. Chill filtration is one of those terms related to Scotch whisky that gets thrown around a fair bit, but what exactly does it mean?
Let’s start at the beginning. For whisky that is below a certain ABV (the threshold is around 46%) if it gets chilled, a cloudiness within the liquid can form. It’s not harmful and doesn’t appear to change the flavour of the whisky, but it does alter the aesthetic and can make the dram appear unappetising, or at least different from what the drinker expects. The cloudiness is caused by fatty acids, proteins or congeners solidifying at those colder temperatures whilst the rest of the whisky remains in its normal state as a liquid. While it’s not a major issue, it can still turn drinkers off, so how do you stop this happening?
Enter chill filtration. It’s a relatively simple process that can employed by distillers to remove the components that cause the cloudiness or haze without impacting the whisky as a whole. It involves chilling (hence the first part of the name) the alcohol at the pre-bottling stage down, usually to between 0 and 3oC which purposely causes the compounds to form so they can be filtered out (hence the second part of the name) through a fine filter or mesh. The now filtered liquid can be bottled and sold as normal without the worry of what the end product will do when it meets the chilly winter Scottish nights or an ice cube (or 2). The removal of the fatty acids also gives the distillers confidence that they’ll get a consistent product at the end which is vital for many whiskies. Chill filtration is intended to be a purely cosmetic operation with distillers who employ the technique reassuring consumers that the flavour, aromas or anything else aren’t impacted. Others are less sure and argue that the removal of anything from the whisky will have some sort of knock-on effect.
The answer? Well unfortunately nobody really knows, and the science isn’t conclusively clear. Given that the process is taking something away from the whisky, even if minor, it seems plausible that it does change what is going on with the whisky. It might not even be the taste, flavour or aroma, but maybe the mouthfeel. It’s worth noting too that the Scotch Whisky Association don’t permit any processes that change the flavour of the whisky so if chill filtration was doing that, it would no longer by Scotch whisky. Ultimately, whatever change is happening is perhaps it’s not enough for the casual drinker to notice so rest assured, any change is going to minor at the very most.
If chill filtration can have a positive cosmetic impact but likely does not affect the flavour or aroma, why doesn’t everyone do it? Well, it’s probably two-fold. Firstly, it’s not cheap to cool a vast volume of whisky and run it through a filter before bottling it. That means distillers will only be doing it if they really feel there’s a need. Perhaps it’s a bottle going to a market that demands clear, unclouded whisky at all times. Maybe it’s a whisky that is more commonly had with ice. It could be off to colder climes. For some distilleries, particularly those shifting big volumes of a specific age statement or collection with a lower ABV, having a known and predictable level of consistency is key. If your production is based around any of those reasons, it’s likely worth your time and effort to invest in chill filtration. Otherwise, it’s a big cost for marginal gains.
The second reason is purely a marketing one. Some folk out there will push non-chill filtered whisky as “purer” or “superior” and likely will charge you more for it or use it as a marketing ploy. There’s no reason to believe that’s the case. Cloudy or hazy whisky does not equal bad or off whisky. I’d go as far to say that if a whisky’s sole selling point is that it’s not chill filtered, it’s probably not worth your time. But you can almost be sure that if a whisky is non-chill filtered, that will be made clear on the bottle.
There we go, an introduction to chill filtration. It might sound ominous, but it’s straight forward and is part of many whiskies basic production process. Not all whiskies need it, not all whiskies want it. But some do and their reasons are perfectly reasonable. It won’t likely change how you enjoy the whisky, and in the vast majority of cases, you’d never be able to guess. However, it’s worth keeping an eye on where you see chill filtration mentioned and consider the reasons behind why a certain whisky has or has not been chill filtered.
Sean black - Freelance writer 