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E-pistle 2007/049 – Ask an Anorak: Bottle Oxidation

E-pistle 2007/049 – Ask an Anorak: Bottle Oxidation

Johannes: I’ve recently received an interesting question from Gunnar Thormodsaeter from Norway.
He was wondering about oxidation inside the bottle – a topic that has been discussed here and there in several E-pistles and the Beginner’s Guide on Malt Madness. I don’t think we ever had a proper group discussion, though. So, let’s take this opportunity…

Gunnar: What goes on in an opened bottle? We have probably all noticed: Once a bottle has been opened, the whisky may change more or less during some period of time, due to the air exposure. Different whiskies react differently, and some more than others. Generally, my own experience is that – pouring a dram or three a week – there usually will be a detectable positive effect to begin with; say the first couple of weeks or up to a couple of months.

The change can be considerable: I score my whiskies, and I would say an improvement of 3 points from the freshly opened bottle is not uncommon. In more rare cases there can be as much as 5 or 6 points difference. (This seems to be either underestimated or simply ignored in published reviews). The whisky opens up and shows more complexity. As long as there’s more whisky than air in the bottle, then nothing more happens for quite a while. Sooner or later though, a negative effect will be noticeable; the whisky will slowly become flat and dull. This may occur after about a year, but sometimes allready after maybe six months or even sooner. (There are a few obvious variables here: How much air there are in the bottle at any given time, and how often the bottle is opened and the air is renewed).

As you have mentioned briefly in your old Liquid Log somewhere, Johannes, different whiskies react differently and in varying degree to the phenomenon, and exactly which factors that are at play here is perhaps difficult to establish. You mention type of cask (bourbon/sherry), phenol level and age. I guess tannins maybe could have importance too. When age is concerned, I really can’t draw any conclusions at all from my own experience. But a layman’s guess would be that young whiskies, since they haven’t already been breathing in the cask for that long, will 1) be more sensitive than older whiskies to the early, positive effects, and 2) endure a longer period of air exposure than older whiskies before they decline. But then there is the influence of the cask. If that in some way has a preservative effect, then probably older whiskies will withstand air exposure better…

And what about the cause? I used to believe it it all had to do with oxidation myself.
Bringing the subject up in the newsgroup alt.drinks.scotch-whisky a few times have given limited feedback, but one “mdavis” there pointed out that the evaporation of volatile components should be concidered as well. Referring to what goes on during the 5 to 30 minutes in the glass (the development of the “nose”), I’m sure he is right. As for an opened (but corked) bottle, I still believe oxidation to be the main cause. But maybe there is a combination? Well, changes occur, that’s for sure, and I’ve been intrigued by this for some time now. Strange thing that a few weeks in an opened bottle can make so much difference with whisky that has been breathing in the cask for many years. I’d love to see you guys elaborate a bit on the subject!

Cheers! (Gunnar Thormodsaeter, Trondheim, Norway)

Johannes: Interesting question, Gunnar – I haven’t found a ‘definitive’ answer myself yet. It’s a topic that deserves a serious investigation, like the glassware tests that Lawrence and Craig did for Malt Maniacs #103 last month – or indeed Ho-cheng’s water test in this issue. But so far I haven’t found the time to organise that yet. So, I’ll put it on my ‘To Do’ list – I plan to add a comprehensive section to the ‘Advanced Beginner’s Guide’ that I’m working on. I guess the main issue is to NOT to mistake changes from day-to-day (changes in perception, but influences of the weather and food as well) for changes in the whisky. So, it’s important to make a certain comparison more than once before making any strong claims. But because of the major role of perception in the process, it’s hard to approach it scientifically…

Your observations match those of American maniac Louis Perlman who already commented on the phenomenon in the 1990’s.
He was mainly interested in the effects on the short term at first – the need for bottles to ‘break in’ for a few weeks before they reached their peak performance. That makes sense, because Louis often finished his bottles quickly. But as the percentage of thrifty maniacs grew, so did our collective interest in the long term effects. Put simply: we all wanted to know how long we could keep suckling from a bottle.
One very general observation in that respect it that sherry matured whiskies seem a tad more vulnerable to time – like wine.
But before I’ll go into other ‘long term’ aspects, I’ll ask the input from a few of the other maniacs…

Davin: Hi Johannes & all, I think Louis did a piece on this some time back.
I have not found that all whiskies change in the bottle, or at least they change at very different rates.  I found the PC5 improved decidedly after a couple of weeks, but I have a Talisker 10 that has not changed in about four years (not sure how long, but it’s an old label bottle). Still I try to finish up bottles once they are opened.  What really surprises me though is just how quickly whisky deteriorates in sample bottles.  I find that pouring whisky off into a sample bottle really accelerates the degradation process.  Especially with light whiskies and non-peated.

After a few months or so I often detect significant oxidation.  Have others observed this?
I mean in sample bottles that have been opened, sampled then half put back for re-sampling later.
Especially true back when we used to exchange larger samples than the 50 or 60 ml standard we use now.
Just my tuppence.  Others?

Louis: Yes, Davin remembers correctly, I have noticed this effect almost since day one of my SMS career.
Many of my bottles have required ‘break-in’ for anywhere from two weeks to two months. Because of that, I don’t make serious judgments about ANY malt until it has been open for that long. There are a couple of variations, sometimes the malt just needs to snap into focus, other times, the various flavor components stand out by themselves. I observe this most often with peated whiskies, but that just may be because I buy more bottles of peated SMS. A couple of Bowmores never settled down, and drifted continuously until they were finished, but I am not trying to start another FWP controversy. Sherried malts have tended to converge to a generic Speyside profile if the bottle had been opened for a long time. And I would definitely agree that once a bottle gets down to the 3/4 empty, it should be finished off quickly, although this can be painful for an expensive and/or rare bottle.

Interestingly enough, while I was standing at the Glenfiddich table at Whiskyfest last fall, someone was telling the reps that he experienced the exact same thing with a recent bottle of the GF 18. They had never heard of it before, but he claimed that it had improved dramatically over two months or so. Johannes, If you’d like, I can try to come up with a list of bottles that either required break in, or that changed dramatically after being opened.

Robert: Me too finds this phenomena interesting and definitely worthy of discussion.
To me this has happened most clearly with (lower proof) bottlings with sherry in their recipies. These can turn bland, flat or “teaish”.
This does not seem to happen as clearly nor as often with bourbon matured stuff. Also it seems to happen that some peaty whiskies loose their oomph while others keep it. Weird. Anyway, to minimize the risk of this happening I do as many others and pour my big ones into smaller bottles when the levels turn low (say ~30%). Also sample bottles are rebottled to smaller ones in case I don’t plan to finish a big sample anytime soon as I share Davins opinion regarding bottle changes in not-full sample bottles too.

Ho-cheng: I’ve experienced the same thing. But not to every bottles. As Davin’s said, PC5 is a very nice example recently.
It needs about 1~2 weeks to open up. My experience showed that single cask bottling, especially sherry casks, tend to need some time to open up.  The interesting thing is that we don’t need to really open the bottle. But just as Gunnar said, we only need to pour a dram out, to leave some space in the bottle. For me, if I am going to lead a tasting, I tend to open the bottles several days in advance and try it. It is not only to be familiar with the whiskies, but also to let it breathe for a while.  Many of my club members tend to taste only half in the tasting and bring the other half home, for the second chance.  Sometimes they found positive changes.

I remember one of my friend asked the same question to Charlie when he visited Taiwan last year.
Charlie found the air space in the bottle has some affect the speed of the whisky oxidation.  But I remember he doesn’t really believe whisky need some time to open up. Whisky does oxidize, we’ve discussed several times. For people like Krishna and me who live in tropical countries.  Even un-opened bottle may oxidized. For me, if I didn’t finish a whisky in the summer time. It will turned sour for just over night.

BTW, I think this effect is not for nosing but for tasting.
I think nosing will be detectable by a drop of water to open it up.
But some bottles need some time to open up and it taste dramatic different.
And I also agree it sometimes changes the scores a little bit, but not always.

Johannes: Quite right, Ho-cheng! Oxidation seems to affect some whiskies more than others.
Well, I guess that makes sense. After all, the chemical composition of each single malt whisky is unique, and some of those compounds will react more actively with oxygen than others. So, this adds a whole new layer of complexity to the wonderful world of whisky.
And a very good point about the climate as well – temperature and humidity are important factors as well…
Any other input from the other maniacs on this aspect?

Krishna: Temperatures where I live vary from 10 degrees (in winter) to 45 degrees in summer.
Right now it is 41 degrees outside and the inside non- A/C room, temperature is a few degrees lower. Can you expect good malt whisky to withstand this huge temperature variations? As I said before, I keep my bottles in a refrigerator and this too has a a limitation. Frequent opening, taking small quantities, keeping it back in the refrigerator – all these take toll of my whisky and gradually my whisky deteriorates so much that it becomes undrinkable. The non – chill filtered stuff deteriorates faster than the chill filtered whiskies due to obvious reasons.

Recently I was told by a net -friend that the vibration of the refrigerator also effects your whisky.
There are so many constraints to store and enjoy a good malt in India, the only way is to finish them off as quickly as you can.

Olivier: I keep my bottles in my cellar ‘ante-room’ that most of you have already seen. Temperatures variations are very limited, from maybe 17°C in winter to 20°C in summer at the hottest, and there is basically no daily variation. Humidity is quite high (not quite enough for a wine cellar though), so I have to wrap the bottles in a protective film to protect the labels from rot. The system works quite well. I feel that a room which is too dry and/or to warm will accelerate evaporation on older bottles with weaker closure systems, especially with big daily temperatures variations, that will put a big stress on the corks or the seals of the screw caps.

Evolution of an open bottle: yes, absolutely yes, I do see a positive evolution after a few weeks of opening the bottle.
Especially if there is 20-25% missing in the bottle and if it is a cask strength whisky. I try not to keep open bottles for more than a year if there is less than 40-50% in it and especially if it is an older lighter style. I decant the left over in smaller bottles, which in turn can be kept a long time after, or, drink them!

Michel: About the same here as Olivier’s situation, except for the cellar that is…
After opening a bottle I will monitor it quite closely for a week or two and see waht happens. Sometimes the changes are dramaticly – that includes negative changes especially with old bottles, which means I invite some people to empty the bottle ASAP – the Talisker we had on the Filling Party essentially disintegrated after two weeks. If the malt shows next to no progress I will leave it for a month or two and return to it. I had some very pleasant surprises here, but also some major disappointments…
When the level is down to about 40% I decant into 6 and 3 cl botlles…

Excpeptions are the whiskies that failed to impress or left me indifferent.
I leave them in the bottle and every now and then I try to see what happens when it’s kept for a longer time (1 year +) in a bottle with a filling level lower than 10% or so… Just to know… What amazes me is that in quite some cases non-peated, low ABV, chill filtered, bourbon casks seem to have eternal life, or at least keep their subtleties while the peated ones can become ultra flat. Gezondheid!

Olivier: Michel, regarding that excellent BBR Talisker: you forgot to mention that you also drove back home from France to Holland with the bottle open. Maybe transport was to brutal for this old malt (low strength also…)…

Michel: Olivier, I guess it only shows how fragile that Talisker was…
If this was ‘normal behaviour’ for old bottles the guys from Dutch Connection are in big trouble every time they move their bottles… From the other side… I suddenly have this image of ‘a certain trader we talked about during Pit’s breakfast Session at Limburg’ doing a Paris-Dakar before offering his bottles… 🙂

Luca: Temperatures inside my house in Torino range from 23 degrees (Celsius) in Winter (damn centralized heating… I’d prefer 21), to up to 32 degrees in Summer (I like air conditioning at work, but I prefer not to have it at home). Let’s say that 9 months per year the temperature stays under the 24 degrees threshold. So far I haven’t experienced DRAMATIC changes in taste, but I have experienced subtle or moderate ones. It must also be said that during summer I tend to have very few opened bottles in my cabinet (I finish the opened ones before summer comes). It must also be said that rarely a bottle stays open more than 4 months: it usually is finished before that time (by me or by friends who come and visit). Usually I have found PLEASANT changes: especially in stuff that was young heavily peated and pleasantly softened up a bit with time, or that was heavily sherried and then became richer and more voluptuous.
Yes, it usually is a softening, but a pleasant one…

Craig: In Adelaide the temperature range is from 10 degrees Celsius in winter to 43 degrees Celsius in summer.
We’d have 12-15 days per summer over 35 deg C) but it’s very rare to get 4 or 5 days in a row over 38 deg C.
When it happens plants in the garden start to die.  We’re in the middle of a big drought here (although it has started to rain in the last couple of weeks) so we’re on third stage water restrictions which means we can only water our lawns one day a week.

I don’t do anything special with my open malts – they’re kept on a traymobile in my lounge room,
which isn’t the coolest room but doesn’t get any afternoon sun either. Air-conditioning (evaporative only) isn’t on during the day as both Rosemary and I work during the day on weekdays. We probably use air conditioning maybe 40-50 days between November and March. All my unopened malts are kept in cupboards either in the lounge room or the Lyne Arm Malt Room (my family/tasting room).

On the open bottle effect – I agree with everything everyone else has said.
Almost every one gets slightly better after a few days/weeks open.  With some it is profound.
The only caveat is those that are unpleasant to start with (oxidized or corked) which stay nasty.
I agree with the observation about bourbon matured malts remaining constant or hanging together longer than sherry matured malts. Finishes almost always get a cardboardy edge. I think they start to disintegrate when they are over 12 months open and less than 50% full; and the older they are the more pronounced the drop off. Old low alcohol malts are fragile and I don’t know why but the natural cask strength ones (even if the bottling strength is less than 45%) seem to last better than the ones where they’ve been cut prior to bottling.

Johannes: Thanks, fellows. I think we’ve covered most of Gunnar’s questions along the way – and dragged up a few fresh ones.
For example, there seems to be a difference between oxidation in A) a cask, B) a bottle and C) a glass.
Interesting… Why would that be?

Well, I guess that’s a topic for another time. The publication date of MM#104 is nigh and I need to wrap up this issue…