Premature Oxidation Research – an update



“In recent years the BIVB have been much more forward and pro-active at bringing new research to vignerons via conferences and their bulletins, but clearly some of the ‘old school’ don’t or won’t want to be told.”

That was the interesting quote of a lady vigneron a couple of days before I visited Jean-Philippe Gervais, director of the BIVB’s technical centre in Beaune. It also underlines the complexity of finding a solution to a problem that appears to have more than one root cause, plus the social dimension noted above.

Following-on from the data that the BIVB last shared with me/us here (half-way down the page); these are my notes from a visit on 15th October:

bivb-technical-centreThe technical centre is also an information resource for vignerons; J-P.G showed me the extranet of the BIVB (all producers can have access) where they monitor 200 different parcels up and down the Côtes for sugar and acidity levels which they can then compare versus other vintages, compare parcels, compare versus precipitation or temperature levels etc., etc. – a cool tool! The tool is also linked to the weather forecast ‘helping the vignerons make the best decisions, not just harvesting decisions, but also throughout the year for treatments’.

I took a short tour of facilities that include:

  • A tasting room ‘for sensory analysis’, no windows, controlled environment.
  • A large cuverie set up for multiple micro-fermentations – in this case generally 50-200 litres

To get an idea of what happens in this large space – maybe with as many as 100 fermentations taking place simultaneously – when I visited, for instance:

  • There were multiple fermentations made from grapes taken x-days before, to y-days after ideal harvest dates to characterize their differences and, for instance, to calculate the optimum sulfur levels in each case. (For every vintage it is different.)
  • Additional samples were in preparation with different levels of oxidation before sulfuring
  • Others characterizing how much oxygen each handling operation introduces to the wine etc., etc.

The resultant wines are then bottled and stored in different temperature-controlled environments, for later analysis.

The BIVB mainly use a non-destructive method for testing the oxygen content in the bottles – i.e. without needing to open the bottles – so this could be, for instance, a measure of oxygen transport through the cork. The team also stores the same wines with screw-caps as a comparison.

It was good to see how the BIVB are working on the problem from a practical sense, and based on previous reports they do not make this work in Burgundian isolation, other universities around the world are part of their research.

Before I make a quick summary of the position today – because there is no great change from earlier this year – it is worth pointing out two important internal measures of the BIVB:

  1. It was the SAQ (Suivi Aval Qualité) quality checks that initially alerted the BIVB to oxidation problems – before consumers started pointing to a problem – and these SUIVI statistics are indicating a lower incidence of oxidation for recent vintages.
  2. And slightly out-of-scope for this discussion (but similarly important) the BIVB’s own internal opening of many thousands of bottles has always recorded the number of corked bottles; in the last 10 years or so their rate has reduced from almost 8% of bottles to almost 2% – my own numbers were about 7% to 2% – we should all rejoice, but the cynic in me cannot avoid the thought that if cork wasn’t under such competitive pressure today, we would still be at 8%!

The list of underlying and potential contributory factors remains relatively consistent. Clearly white wines have always oxidised, but today the incidence is on a much higher level, however, in our modern world of instant communication, there is no place for bad wines from gifted terroirs to hide…

There is no single truth, but the following remain constant:

  1. Some premature oxidation can be traced back to how the people work and the consequent amount of oxygen they are introducing to their bottles – there are significant differences possible – clearly this is not new and must have been the case for many producers and for generations. However, given that (see below) the base raw material seems to have changed over recent vintages, this dissolved oxygen may have a much more pronounced effect in the bottles than it did 20 years ago.
  2. From analysis, it is clear that the chardonnay juice that browns a little during/after pressing, loses this colour during fermentation and is (later in the bottle) more stable to oxidation than a must that is instantly sulfured and not allowed to ‘brown’. Some vignerons today describe this as a micro-oxygenation step.
  3. Fragile grapes with botrytis are sometimes treated with enzymes later in the elevage to ‘clean them up’, but this also renders the wines equally fragile in terms of oxidation.
  4. Pressing too lightly can certainly deprive the grape-must of polyphenols that will normally have an antioxidant role either in the lees or, due to lees contact, later in the bottled wine.
  5. Too fast an elevage may reduce the impact of any antioxidant effect of polyphenols resident in the lees, as they are simply in contact with the wine for less time.
  6. A simple visual inspection of the relative sugar and acidity levels of mature grapes in different vintages starkly show – despite the naysayers – that the grapes harvested in that last years are certainly different, and consistently so, to those harvested 20 years ago. Whilst it is clearly possible to challenge the data, as represented it looks to be the beginning of a strong case. [here.]
  7. Finally; let us not forget that temperature does make a difference to the onset of oxidation, storage at 20° being much worse than 12° for instance – so transportation can also have some bearing – though this is clearly not a factor in many cases, i.e. where bottles have never left their producer’s cellars.

Some further reading for you here (pdf).

My Position:
The BIVB remain faithful to a number of mechanisms, which when taken together, form the basis of what they believe will be a solution to what has been termed premature oxidation; I am minded to believe that their ‘total approach’ does make sense from a scientific perspective.

Despite my training as a scientist, and having a measure of ‘technical comfort’ about what the BIVB can demonstrate, I’m afraid that I’ve spent enough money to remain circumspect – I, and I suspect much of the market, will still need harder evidence of improvement, i.e. the empirical kind. And when will that come? I expect not before the 2007 vintage, and more likely that of 2009(!) From a consumer perspective I would not yet change my advice to drink all white Burgundy by its 6th birthday to avoid disappointment.

To finish, I’d like to refer you back to the vigneron’s quotation that started this short article; the BIVB can ‘take a horse to water, but they can’t make it drink’. Individual growers who do not show an improvement can only be forced to do so by the market…

Agree? Disagree? Anything you'd like to add?

There are 6 responses to “Premature Oxidation Research – an update”

  1. T Carson29th November 2010 at 12:46 amPermalinkReply

    Not one mention of the closure? How ridiculous not to investigate the role of the cork….we in the new world have eliminated rampant oxidation problems in white wines by changing the closure to screw cap!
    It is the consumer that is losing here, you might as well double the price of the white burgundy you are purchasing as the failure rate, after just a couple of years in bottle, it that high.
    Wake up Burgundy!

  2. Fred Schilling29th November 2010 at 1:34 amPermalinkReply

    Many thanks, Bill. Disseminating info about the state of the sporadic/random/prem oxidation art is very good for us interested consumers but more detail would be great. I realise that the BIVB don’t want to scare the horses any more than necessary but the trend of increasing sugar and reducing acidity as vintages go by must lead to treatment and handling changes for the must/wine if chardonnay is to age med-long term, don’t you think?

    Have/will the BIVB release outcomes of the differences that they have found between cork and screwcap sealed bottles of the same wine? Presumably, they have been doing this comparison for some years by now and have something useful to say about that.

    Fred S

  3. Peter Godden2nd December 2010 at 12:34 amPermalinkReply

    Personally, I take no comfort in knowing that ‘only’ 2% of Burgundy is corked (my emphasis). And why didn’t they come clean on the 8% figure years ago? That is similar to the figures that the AWRI was consistently seeing and talking about in Australian and French wines from the early nineties through to the mid 00s when screwcaps took off in Australia, and if other organisations had provided support at that time the cork industry would almost certainly have reacted sooner and much more forcefully. Yet we saw mainly denial, particularly in Europe, and it seems that in this instance little has changed. Think of the millions of corked bottles, dollars wasted and dissatisfied consumers which could have been avoided. Yet hardly a mention of closures in this article. TCA, combined with ~50% of the white wines being undrinkable after two or three years due to oxidation, almost certainly due to the closures in most cases, is why I stopped buying white Burgundy years ago. Until I can get the wines I want under screwcap or other reliable closures, that will remain my position.

    • billn3rd December 2010 at 5:48 pmPermalinkReply

      I guess some people see the glass half empty Peter – I see 75% less corked bottles.

      Interesting that (from your text) you imply it’s a burgundy problem that they should have published – whereas I simply see confirmation of my belief of the level of a global issue that is/was completely independant of burgundy.

      I have no horse in the closure race, yet believe there is nothing to match a perfect cork – it’s just a shame they are hard to come by…

  4. billn4th December 2010 at 8:52 pmPermalinkReply

    @Fred Schilling – Hi Fred, I only give you the information that I’ve teased out and that that won’t get me in jail 😉
    Re cork/screwcaps; that is ongoing, so no.
    Re changes in handling; sofar it’s more about returning to what they did before – decent pressing, retaining much of the lees and not rushing elevage. Will that be enough if the base material really is changing and environmental factors are responsible? The $64,000 question. Maybe they really will have to go to the space-suit approach to bottling already employed by the likes of Bouchard Père

    @T Carson – Where to start.

    How ridiculous not to investigate the role of the cork

    It is more ridiculous to lose objectivity.
    You nail your colours to the mast whilst studiously ignoring the fact (as above) that such trials are stated to be ongoing, including the tests that determine oxygen transport through the corks into actual bottles of wine. You also don’t seem particularly interested in the empirical demonstration that cork was (reasonably) okay pre 1996 – note, I don’t say consistent. The BIVB research has majored on ‘what has changed’ (my interpretation) and then how to fix it. Without such a fundamental approach / research / gained knowledge, what will you do if screwcaps are no longer the answer? I am frankly agnostic on seals but have never accepted that ‘they’ are the root cause of all today’s oxidation problems – that is head in the sand thinking no better than the ‘cork forever’ brigade. I don’t understand your last sentence, unless you are saying that the effective price is double – with this I cannot disagree; depending on how long you wait it could be as much as a total loss. Note though, that ‘two years’ is inaccurate; for P.Ox you are talking 5-6 years post-bottling, 2004s are the youngest to come under the microscope…

  5. Rick Dalia5th December 2010 at 6:47 amPermalinkReply

    I am the weak-minded fool, the sailor that cannot… will not turn away from the call of the siren. My cellar will not be devoid of white Burgundy left to slumber for 6, 7, 10, 12 years, more.

    Under screwcap, I’m wondering if there might be a retardation of the desired aging process. It is my belief that whatever exchange takes place between the wine and the outside environment during the years at rest are pivotal and necessary for a wine to develop as it should. The cork, of course, is not impermeable and is the membrane through which this exchange takes place. Is the goal maturation or stagnation?

    • billn5th December 2010 at 9:14 amPermalinkReply

      Hi Rick
      Screwcap can give you a range of permeabilities – or none if you go for a metallised insert. I have some screwcap burgundies from JC Boisset (whites) and am quite happy with what I’ve seen, but then I also have wines from the 60s-80s in my cellar (reds) for which I’d want a little empirical evidence – no different to seeing with my own eyes plenty of 10 year-old white burgundy where 50%+ are not oxidised.

      As I understand it, wine-making (at least the regime assocaited with the wine at bottling) would have to change as the screwcaps seem to deliver quite a reduced wine – given the amount of CO2 already in the wines today, I’m not sure of the compatibility…

  6. Fred Schilling5th December 2010 at 9:06 amPermalinkReply

    Hello Bill,
    perhaps you can be a mole for WikiLeaks and release what you’ve found from the BIVB on that site ;-). Much more interesting than confirming that diplomats are a bunch of gossips that like slagging off heads of state (probably with good cause).

    Looks like you’ve attracted the attention of three Antipodeans in raising the problem of premox. Years ago we just called it bottle variation and shrugged it off as one of the vagaries of using tree bark as a wine bottle stopper. We now know better. Bottle variation is not something that consumers should accept unless there is cask by cask bottling, different batching or similar. My own experience is that screwcap = best cork, so far as I can judge, but some tweaking of bottling chemistry relative to that for cork is needed if it is to be done well. Diam/Diamant cork seems to be very good also for those traditionalists not prepared to go screwcap (long term under Diam still to be assessed, I think). A facet of cork which is little mentioned is the cork-wood leachate flavour and phenolics which are most noticeable in somewhat delicate flavoured unwooded fruit-acid balanced whites such as riesling, Hunter River semillon and sparkling wines – another good reason to move away from cork unless actively seeking those variable “woody” notes as the wines age.

    The AWRI (Godden et al & etc), at least, has done extensive closure trials not to mention the in-house ones by many producers. For the BIVB to be belatedly repeating closure trials is fine for their own data collection but there is already a wealth of knowledge and experience out there to be drawn upon.


    • billn5th December 2010 at 9:26 amPermalinkReply

      Fred – the problem would be Swedish court 😉

      Actually the antipodeans seem to be railing against cork – like normal – probably because they are having a tough time in the cricket. I think focusing on closures to the exception of other factors – in respect or p.ox – is a bad approach, nothing more. And note BIVB are doing trials that focus on p.ox, it is one thing to have an appreciation of oxygen transport, but that will be in the AWRI case on corks as delivered at that time (1990s?) as we can see, corks must be treated differently today as the TCA incidence is lower – so not exactly the same beast…

      One version of Diams are now guaranteed to 10 years which is pretty good, and there’s no TCA – Bouchard Père are already using them for their GC whites in half bottles. One vigneron did mention to me this week that there might be an issue with phthalates in the DIAMs – I haven’t heard that anywhere before.

      One interesting last snippet this week came via a cork supplier who believes the focus is wrong in terms of the use of H2O2 in bleaching corks; his proposition was that the peroxide itself had nothing to do with oxidation (I have also argued this because the half-life is relatively short), but rather its action on the interior cells could have affected (after about 5 years) the elasticity of the cork. I’m unsure because I’ve seen spongy and hard corks, both with an oxidised wine – anyway, for info…

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