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The Cold facts (and an opinion) on Chill Filtration

The Cold facts (and an opinion) on Chill Filtration

(Non) Chill Filtration! A blessing or a curse to whisky?

Here's what a non chill-filtered whisky might look like if it gets cold. 
The haze is caused by long chain fatty acids and esters (aka flavour compounds) clumping together in cold temperatures. Because they are less soluble than alcohol they become visible as a cloudy haze - it's not a very attractive look and once upon a time it led to customers sending the whisky back to their suppliers, in fear that the liquid had 'turned', or gone off in transit.

Fear not though - once the whisky comes back to room temperature the acids and esters happily go back to their normal state and become clear again.

Battling the Haze

There are a couple of things that distilleries and bottlers can do to prevent the haze in a cold bottle - or for that matter, in a glass when a splash of cold water or ice is added - because believe it or not, this is when most people actually see the impact that the cold addition has on the look of a whisky.

The first thing they might do is bottle at a higher ABV. Simply put, the stronger the strength of alcohol, the 'warmer' the whisky stays.

While chilling whisky may have a visual effect in any strength or a small period of time, it lessens drastically if the whisky is above 46% ABV. Alcohol acts as a solvent, and the higher the ABV, the better it can keep these compounds in solution, preventing haze formation.

When whisky is bottled below 46% ABV, the reduced alcohol content makes it harder for these compounds to stay dissolved. If the whisky is then chilled or diluted, they can precipitate out, causing cloudiness. 

This is why you will see many whiskies, (certainly from new, small, craft or independent distilleries and bottlers) bottled at a strength of 46%. It has become a volume that whisky fans look for almost immediately on the packaging, even before age or cask style.

It dilutes the whisky with enough water to expand the quantity available for bottling, while giving more perception of strength and natural treatment. But let's not forget that every whisky will go through a natural filtration process.

Even at cask strength, casks are emptied in cold stores, from cold casks, and are filtered to remove oak debris. If cold enough, this could also hold back flavour compounds.

The other method used for reducing, or removing the haze on a whisky, is a process called Chill Filtration.

Chill Filtration is an additional process used by many distilleries to remove the 'offending' compounds, fatty acids, esters and proteins. 

Here’s how the process (simply) works:

  1. Cooling the Whisky: The whisky is cooled to a temperature between 0°C and -4°C (32°F to 25°F). This cooling causes the fatty acids and other compounds to solidify or form microscopic particles.

  2. Passing Through Filters: The chilled whisky is passed through fine filters, often made of cellulose or other specialised materials. These filters trap the solidified compounds while allowing the liquid to pass through.

  3. Rewarming: After filtration, the whisky is brought back to ambient temperature before being bottled.

Chill filtration is not unique to whisky. It is also used in other spirits and beverages to improve clarity and consistency. The process is applied to remove compounds that may cause cloudiness or sediment, particularly when the liquid is chilled. Here's how chill filtration is used in other drinks industries:

1. Spirits:

Vodka: Chill filtration is common in vodka production to ensure a crystal-clear appearance and smooth texture. Since vodka is typically not aged, the filtration focuses on removing impurities rather than preserving flavour.

Rum: Some light rums undergo chill filtration to maintain a clear, polished look, especially when served cold or mixed in cocktails.

Gin: Though less common, certain gins may be chill-filtered to remove botanical residues or oils for a clear appearance.

2. Beer:

Chill filtration is sometimes used in brewing to remove proteins and other particles that can cause a hazy appearance, especially in lighter beers like lagers. However, craft and unfiltered beers often skip this process to preserve flavour and texture.

3. Wine:

In winemaking, a similar method called cold stabilization is used to remove tartrate crystals that can form in the bottle. This process ensures clarity but doesn’t significantly alter the wine’s flavour.

While chill filtration is widely used, its necessity and impact depend on the desired characteristics of the beverage.

The Pro's and Cons of Chill Filtration

Pros:

Chill filtration ensures that whisky remains clear and bright, even when chilled or diluted with water. Without this process, whiskies containing natural oils, fatty acids, and proteins can appear cloudy or develop sediment when temperatures drop. While these changes are harmless, many consumers prefer the clean, polished look that chill filtration provides.

Chill filtration allows more consistency in colour and in appearance. It also means that more water can be added without fear of becoming aesthetically displeasing. For the distillery this means more whisky can be released.

Cons:

Simply put, you can't put the whisky through this severe process without affecting something. Many distilleries argue that the consumer can't taste the difference between a chill-filtered whisky and a non chill-filtered whisky. So if it's not the taste that changes, what does?

The arguments here depend on whisky to whisky, person to person. Personally I feel that the change comes in the mouthfeel - ultimately the 'experience' of a whisky. If you put two identical whiskies, bar the filtration, side by side and focussed purely on tasting notes, I expect the notes to be very, very similar. However the experience of a non chill-filtered whisky should be 'fuller', oilier and thicker.

Alcohol oils will stick to the inside of your mouth, lengthening the finish and keeping flavour in your mouth.

Conclusion

That's the theory anyway! There are, of course, many, many excellent whiskies bottled at 40% ABV with exceedingly long finishes. There are distilleries that produce and bottle global giants at 40% or 43% ABV that are successful because they are more refreshing, lighter and bright.

As a new drinker to whisky, one might prefer something lighter in alcohol - our biggest selling entry level whiskies are bottled below 46% ABV. Think Glenfiddich, Glenmorangie, Balvenie and MacAllan for single malts, as well as Chivas Regal, Johnnie Walker and other hugely successful blends, including our own best selling blend - Adelphi Private Stock.

Chill Filtration is a long way from being a negative - only a real whisky snob would say that it is, but it does remove some natural elements of the whisky that gives the perception of an industrial, mass produced release.

And let's not forget that some whiskies, through old age and maturation, will naturally fall below 46%. It's then a big decision on the distiller to choose whether the bottle will be chill filtered due to their rarity and potential marketability. 

Whatever your preference remember that - it is YOUR preference. It's not right or wrong. Like everything else in this wonderful industry it's a choice that we make based on our tastes. 

Next article Kilchoman's Gone Cask Strength with Two new(ish) Releases

Comments

Mike Pilgrim - January 28, 2025

Thanks Mike, very informative 👍

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