The chill factor

The chill factor

Ironically few subjects are likely to make a whisky aficionado's blood boil quicker than that of chill filtering. Ian Wisniewski presents the arguments

Production | 25 Sep 2003 | Issue 33 | By Ian Wisniewski

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It’s all very well for the militant malt brigade to criticise the industry for chill filtering, but as consumers we also have to take our share of collective responsibility. Okay, not all of us are squeamish, but many consumers would be put off if their dram looked different after adding water or ice.Moreover, the damaging effect this could have on consumer confidence, and perception of whisky as a quality product, not to mention apparently ‘defective’ bottles being returned, provides a valid (if not compulsory) reason for chill filtering. Without chill filtering, whisky bottled below 46% abv throws a cloudy haze either when diluted with water, or when subjected to lower temperatures, such as adding ice.Similarly, whisky stored at a low temperature can result in unappealing precipitation in the bottle (which vanishes once the temperature rises again). The principal culprits causing cloudiness are long chain fatty acids and their esters. Reducing alcoholic strength, or temperature, changes the whisky’s solubility (ie. the ability to hold the fatty acids in solution) and they begin to precipitate out.Consequently, chill filtering ‘protects’ us from this reality, and has been applied to the vast majority of malts and blends since the 1960s. Fatty acids are derived from cereals and yeast cell wall material during fermentation (some of which carries over into the new make spirit). Comprising the largest molecules in whisky, fatty acids are also present in significant amounts. However, the understanding of their effect on mouthfeel and flavour is still developing.Fatty acids are believed to contribute an element of mouthfeel and a minor degree of flavour, although current thinking is that they are more important as ameliorators of flavour.The consequent question is, what effect can reducing the level of fatty acids have on a whisky? While there is no definitive conclusion on the subject, there are passionate convictions. One belief is that chill filtering diminishes mouthfeel and strips out flavour, and should therefore be avoided. Meanwhile, some industry experts state that chill filtering needn’t affect the mouthfeel or flavour of a whisky, and that it all depends on the chill filtration regime rather than the actual process. Consequently, the regime can be tailored to stabilise whisky without influencing the character. Moreover, as various malts and grains would react differently to the same regime, as indeed would a range of malts, it’s a case of finding the appropriate regime to suit individual malts and blends.As chill filtering (not to mention maturation) is an expensive process, it doesn’t make sense to subject whisky to a process that may compromise flavour.An essential preliminary to chill filtering is reducing the whisky to bottling strength. Adding reduction water causes the fatty acid molecules to cluster together, with the subsequent chill making them cluster together in even greater numbers. Chilling is achieved by passing the whisky through a heat exchanger, Which comprises chilled stainless steel plates. A valve regulates the flow rate of the whisky to ensure the target temperature is achieved. This can be around four to six degrees centigrade, with 0, -2 and -4 degrees centigrade at the other end of the scale. Distillers optimise the temperature to stabilise the whisky while maintaining the character (with fatty acid esters precipitating out more rapidly at 4C than flavour compounds).Chill filtering at -4C is rare, and applied to blends rather than malts. While this temperature may sound alarming there are mitigating circumstances. Blends can be – and in some cases need to be – chill filtered at a lower temperature than malts. Grain whiskies have a lower concentration of fatty acids than malts (distilling grain whiskies to a higher strength is a logical reason for this).Blends correspondingly have a lower level of fatty acids than malts, due to the ‘diluting’ effect of the grain whiskies. This in turn makes the fatty acids more difficult to remove, and necessitates a lower temperature.Once chilled, the whisky continues to what is typically a ‘plate and frame’ filter. This features a cellulose pad, resembling blotting paper, which may be impregnated with kieselguhr, essentially fossilised plankton (sea creatures) mined from seabeds.The relevance to whisky is that the kieselguhr initially ‘attracts’ fatty acid molecules, though it’s essentially a case of mechanics as the fine lattice structure is an ideal filter. The flow rate of the whisky through the filter is another significant factor, as this determines the ‘back pressure.’ A faster rate, and higher back pressure, pushes whisky through the filter more forcefully and results in less thorough filtration. Correspondingly, a slower rate can strip out a greater level of chilled molecules. The choice of filter pads also affects the degree of filtration, with filters available in a range of thickness' and densities. The amount of sheets placed in a filter also varies, and sheets with varying levels of kieselguhr are available, enabling distillers to tailor the process to each product.Meanwhile, whatever our views on chill filtration, if we’re only used to a chill filtered whisky, and plenty of them take us straight to that ‘special place’, then what’s the problem? The problem is that we all want to know (definitively) whether various whiskies would taste different without chill filtering. My love of technicalities has brought me to the point of being an enthusiast with the instincts of a vulture, and I would love to have a ‘lock-in’ in various labs to conduct extensive ‘before’ and ‘after’ tastings in order to reach some kind of consensus.Beyond the confines of a lab, Praban Na Linne (The Gaelic Whiskies) provides an opportunity for everyone to undertake a ‘compare and contrast’ exercise, with two versions of Te Bheag blended Scotch, both at 40% abv.While non chill filtered blends are rarer than malts, comparative bottlings such as this are even more remarkable. The chill filtered Te Bheag sports a brown label for ease of identification, with the counterpart bottling featuring a white label with the subtitle ‘Connoisseur’s Blend unchill-filtered.’I look forward to hearing what you think. Praban Na Linne also bottles the Poit Dhubh range of non chill filtered vatted malts, including an 8, 12, 21 and limited amounts of a 30 year old, each at 43% abv. It’s unusual to find non chill filtered whiskies at this strength (46% abv or higher tends to be the norm), with other examples including Wm Cadenhead’s blended Scotch, Putachieside at 40% abv. The Compass Box Range of Asyla (blended Scotch) at 40% abv, Hedonism (grain whisky) at 43% abv and Eleuthera (vatted malt) at 46% abv are also not chill filtered.Meanwhile, more distilleries such as Bruichladdich offer a non chill filtered range, while others offer non chill filtered styles within their repertoire. “We took the initiative not to chill filter Ardbeg 10 years old in the year 2000, in order to cater for the specialist. This is a premium but mainstream product, and we really wanted to give the consumer Ardbeg as close to the cask as possible,” says Hamish Torrie, Ardbeg
marketing manager. This decision also raised another pertinent issue. “Bottling at 46% abv entailed a bit of a risk that some consumers would be put off by the strength, as there’s a misconception among less well-versed consumers that adding water is a sin, so when people see it
at 46% abv they may think it’s too strong.”It was inevitable that more non chill filtered whiskies would come onto the market, prompted by growing demand for whiskies to be bottled in their most ‘natural’ state.Consequently, chill filtering is a hot debate among connoisseurs, not to mention distillers and marketing departments. Not chill filtering is also becoming a more important part of a brand’s credentials, and the way in which it is marketed. While it’s easy for critics of chill filtering to say that the whole issue could be resolved through education, in order to prevent any adverse consumer reactions to cloudiness, how realistic is this when many consumers aren’t even aware of the differences between malts and blends?One optimistic sign is the growing consumer interest in the production methods behind various drinks and foodstuffs, exemplified by the organic movement. Moreover, being told that chill filtering can potentially influence character, and that it’s a relatively modern ‘extra,’ is an evocative enough concept, without having to understand the technicalities.“Whisky how it used to be made,” is a line that Skip Clary, Praban Na Linne’s UK manager, uses successfully to a broad audience. “The company is based on Skye and we get people wandering in who are not necessarily even interested in whisky,” says Skip Clary.“And when we give them a non chill filtered whisky they light up and say: ‘we’ve never had a whisky like this before.’ Our blended whisky is also enjoyed by people who say they are only malt drinkers.” Having met plenty of this type, and even repeated “I don’t do blends” myself, that really is an achievement!
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