Chill filtration: Does it make a difference to flavour?

Can you identify a chill filtered whisky by taste? Two of our whisky lecturers, Vic Cameron and Dr Gordon Steele discuss whether chill filtration impacts the flavour of the final product you drink.

[GORDN] We're going to talk about chill filtration. If I can just introduce what chill filtration is: it's a process by which blended whisky, the temperature is reduced, that takes out a solution some of the longer chain fatty acids which are then filtered out of the whisky and that gives the whiskey great clarity, particularly in markets where ice is the preferred way of serving it. It's controversial because some people says it affects flavour, other - or some - people says it doesn't. Some people says it affects mouth feel, some people says it doesn't. What's your opinion on that?

[VIC] Well, I'm not actually sure because I used to think that it didn't affect flavour; the the science and the theory would probably say it doesn't affect flavour because the long chain fatty acids probably not responsible for flavour or aroma. I do think they're responsible for a mouthfeel. But I remember tasting a 14-year-old Aberlour once, one was non-chill filtered and one was chill filtered and I thought I perceived a difference. Now, I'm just wondering if that was because I knew there was a difference and I was looking for one, or if it was really there. So, I'm not actually sure. I think the theory would say it's not going to affect it, I think it's going to affect the mouthfeel but probably it shouldn't affect the flavour.

[GORDON] I'm of your former opinion. I don't think chill filtration makes any difference to the flavour and I base that on looking at quite a number of samples. One of the issues we had when looking for these samples was to find like - comparing like with like.

[VIC] Absolutely.

[GORDON] That's the that's the problem. So we've spent a lot of time doing that. Trying to find the pre-sample before being chill filtered and then as a sample afterwards. What we discovered, which was quite ancillary to the actual project, was that if you'd made a mistake, as it were, if something had gone on during chill filtration - and that's particularly stopping and starting -that can act as a knock and it knocks some of the larger stuff, larger congeners, through the filter and there will be a difference because of that. But the temperatures that are that are used, I didn't see - or we didn't see - the rest of the team didn't see - any differences between that. We didn't look for mouthfeel, I have to say. We didn't look at that so I think it's an open question.

[VIC] Absolutely and different perceptions as well. I mean, when I did that little experiment, it was in a Visitor Centre and the non-chill filtered was a new expression, more expensive expression and I was kind of being told: this will taste better.

[GORDON] Yes.

[VIC] And you kind of know, sometimes you can be pushed towards something and be suggested towards that this is a better flavour and better aroma. So that's my only experience of non-chilled and chill filtered, so I think that's slightly biased. But like I say, the theory would say no, not a blind bit of difference.

[GORDON] And I really don't think there is. There's also, people forget this, there's a legal responsibility on the manufacturers of Scottish whisky not to change the flavour. And it wouldn't be allowed. You have to ask yourself the question; why are you undertaking this process? If the process is undertaken for the sake of altering the flavour, it's not allowed!

[VIC] It could be deemed illegal!

[GORDON] So, if chill filtering did change the flavour, unscrupulous manufacturers could use it to adjust adjust flavour and indeed, if you got cold enough... One of the caveats I've got is that at the temperature. Chill filter use, at the temperatures that are used within the industry, if you got cold enough, indeed you would start to take out not only the long chains but you start to...

[VIC] Take a lot more.

[GORDON] ...take out a lot more and that would have an effect. But we're really talking about very low temperatures there which are very expensive to... that's not the way you would adjust temperature!

[VIC] So it's probably only going to about 2°C, 3°C is it?

[GORDON] Yes, aha. I mean, different manufacturers have different... depends on the market that the product is going into. But I have seen as low as -5°C, that seems way too low to me. Even that doesn't affect flavour, I don't think. But 2°C, 3°C, zero degrees... fine. And there's different ways of doing the chill filtration which you can. You don't have to chill filter the whole block of the whole vatting. You can just chill filter certain bits of it, so you can do that sort of mix and match as well. But I think it's one of those, there's arguments which which, because marketeers always want to push the non-chill filtered, they say, pushing it as somehow superior

[VIC] I think that's a genius of marketing because chill filtration costs the company to do the process.

[GORDON] It's expensive.

[VIC] But, what they're saying is, if we don't chill filter it, it adds value and we can charge you more! A genius of marketing. And I think it's being done to take away a perceived problem that's not there... because cloudy whisky is not bad whisky, it's a - you know - the consumer is seeing cloudy whisky is potentially a problem... it's just a natural process.

[GORDON] Yes, it depends which market you're in. I would, you know, Chinese, South American markets, even some of the American (North American) markets, the knowledge about Scotch whisky is minimal. All they know is they enjoy that particular drink and they enjoy it. And, so, they expect clear, sparkling liquid within the in the bottle. Particularly as the trend to bottling now has been for clear bottles. We don't see many green bottles any longer, other than a few classics.

[VIC] So, you're seeing the product.

[GORDON] So, you're seeing the product, you're seeing it on show and the shelf appeal is important. And some of those markets are in cold environments, where they might throw a haze. So that's perceived by the consumers as undesirable. Certainly, for the knowledgeable consumer, yes, I agree with you it's not really an issue.

[VIC] But there are consumers out there some, on the other end of the market, that I see: "well i won't drink a whisky unless it's non-chill filtered.

[GORDON] Yes and they're missing out.

[VIC] They're absolutely missing out on some great products.

[GORDON] Exactly. And I think if you look at the history of Scotch whisky, there's this history of of the best whisky somehow... somehow or other, the companies are keeping the best whisky to themselves! You know, first of all, it was 'well they're not letting malts go, are they?' You know, malts were being kept in... and so we supplied malts and malts are now common. And then 'well of course it's single malts that are the important ones' and oh we're now getting single malts. Well it's now...

[VIC] 'Single casks!'

[GORDON] Single casks! 'We can't get them, you know, they're keeping them away'. And now it's, now they're changing the flavour by chill filtering so it's un-chill filtered, un-coloured... This sort of suspicion. Actually, it's the opposite way around. They'd love to sell as much whisky as possible!

[VIC] Absolutely!

[GORDON] And they're not trying to keep the best whiskies. Why would they want to keep the best whiskies away from the market? But there is that sort of perceived we're not getting the real whisky. Somehow or other it's been being kept away from us and chill filtration is part of that process. I don't see it that way.

[VIC] So, I think we're kind agreed, probably.

[GORDON] Kind of agreeing, which is a bit annoying (laughs) we should be arguing with each other! Perhaps, I think, it is unnecessary, say if you have a very rare aged whisky. Why would you want to do it?

[VIC] You want to kind of straight out of the cask, natural or whatever.

[GORDON] And I think very few of them are actually chill filtration. You know, some of the rarities, some of the unusual, say from closed distilleries and things like that... why would you want to do that?

[VIC] Why would you want to alter it?

[GORDON] Why would you want to do that? There's no real need to do it. But I'd say, as for affecting the flavour, I don't think it does affect the flavour. We'll leave an open question about mouthfeel.

[VIC] Mouthfeel, maybe.

[GORDON] I don't see much difference in mouthfeel. I'm kind of unsure what we mean by mouthfeel because often we have whiskies diluted, it's related to strength as well as to, you know.

[VIC] But I think you hit it on the nail, it's quite a hard question to answer. It's getting the like-for-like to compare.

[GORDON] Yes. And we have been able to do that work and that's what really convinced us - or convinced myself - that there is no difference. With the one caveat: that it's done properly, it's done properly.

[VIC] Aye and not too low. Good. So, we're agreed! One, one.