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  • Corks, screw caps and oxygen ingress - the answer at last?

    Hi everyone,

    I'm currently in the midst of penning a screw caps manual for winemakers in conjunction with Jeff Grosset, Michael Brajkovich and John Forrest, initiated by the International Screw Cap Wine Seal Iniatitive.

    In my research I have come across a finding which appears to me to settle one of the big questions regarding screw caps and wine development. Given the fascination with such questions here, I thought you might be interested to know.

    The debate over whether oxygen ingress through the closure is a requirement for proper bottle development has been ongoing ever since Louis Pasteur announced that “it is the oxygen that maketh the wine,” more than a century ago. In recent times, Jean Ribéreau-Gayon and Emile Peynaud have argued the case that wine development is a reductive, not an oxidative process and that the quantities of oxygen that normally penetrate into the bottle are negligible, anyway. Hence, reactions that take place as bottled wine matures do not require oxygen. This has been the case presented by the screw cap lobby.

    The counter-argument to this theory has been put forward by Roger Boulton, who asserts that wine maturation is dependent upon small amounts of oxygen seeping through the cork.

    In Screwed for good? I spent five pages tossing around the arguments. At the recent International Screw Cap Symposium in New Zealand, wine scientist Peter Godden of the Australian Wine Research Institute presented some results which, I’ve since realised, settle the case once and for all. And, in contrast to five pages, I can now answer the entire century-old debate in just one paragraph:

    In a trial of the technical performance of various wine closures conducted by the Australian Wine Research Institute (AWRI), the oxygen permeation through the closure was measured approximately three years post-bottling. The measurements reveal that reference 2 corks permit between 0.0001 and 0.1227mL of oxygen to enter the bottle per day, while screw caps permit 0.0002 to 0.0008mL. Hence, it is clear that the oxygen permeability of the screw cap is essentially identical to that of the very best corks, and is in both cases negligible. The screw cap thus accurately replicates the maturation conditions provided by the very best corks.

    It is universally accepted that the greatest old wines are those with the best corks and the smallest ullages. These are the corks with the very lowest oxygen permeability. The screw cap replicates their performance, not in the odd instance of the occasional “best bottle,” but consistently, for every bottle.

    It appears to me that the AWRI measurements finally settle the debate, confirming that the oxygen ingress through the best corks is indeed negligible, verifying the case presented by Ribéreau-Gayon and Peynaud.

    Many people have been arguing this line for a long time, but the great thing now is that we have solid, scientific, quantitative evidence, and it is no longer conjecture!

    Cheers,

    Tyson.

    As an aside, note the variation in oxygen transmission under cork. That’s a factor of more than 1200, compared to a factor of 4 under screw cap! And these are quality, 45mm corks just three years after bottling. Incidentally, the means were 0.0179 for cork and 0.0005 for screw cap.

    [ January 03, 2005, 06:11 PM: Message edited by: Tyson_Stelzer ]
    Tyson Stelzer

    Wine Press

    Download the Top 500 Wines 2005-2006

  • #2
    i'm very much an advocate of the screw cap revolution. however, can we really declare victory thanks to one study? why can't this initial evidence be presented as promising and/or important and compelling? all scientific breakthroughs are validated and confirmed with multiple, independent, quantifiable evaluations.
    better to die on your feet, than to live on your knees.

    Comment


    • #3
      Thanks for sharing this. It is very interesting. I'm not sure I want my 2003 Latour bottled under screwcap on the basis of this, but it is interesting.

      Jim

      Such blind obedience to the opinions of a single man smacks disturbingly of the masses' weakness for fuhrers who can tell them what to think politically or how to behave in everyday life -- their weakness for "authorities" on everything to do with culture and entertainment.


      -- Michel Bettane, Issue 15 The World of Fine Wine

      Comment


      • #4
        Originally posted by jeff nowak:
        can we really declare victory thanks to one study?
        Hi Jeff,

        If there were scientific evidence to the contrary, I would agree that such an approach would make sense. However, I have been searching for such evidence for three years and am yet to find it. By comparison, I have found a lot of evidence to support the AWRI study results.

        Originally posted by jeff nowak:
        initial evidence
        Research into this topic has been ongoing now for 142 years.

        Cheers,
        Tyson.
        Tyson Stelzer

        Wine Press

        Download the Top 500 Wines 2005-2006

        Comment


        • #5
          I don't have a dog in this fight, but I did take a statistics course once (well five of them, but who is counting).

          Ignoring argument that the amounts of oxygen in question are de minimus for the moment, the numbers on the amount of oxygen allowed by the two closures are not even close. Taking the high end of each range, 0.1227mL is 153.375 times 0.008mL. Plus, did you say that each figure is per day? If so, the 150 times difference, cumulated over a number of years gets to be a very large difference, indeed. I don't think I have a calculator with that many zeros.

          As I said, I have no idea if that amount is negligble or not, but the two ranges are not even in the same ballpark!

          Comment


          • #6
            This is fascinating and in much more detail than I can ever comprehend. This enclosure will certainly gain increasing recognition and acceptance. One thing missing from the screwcap is similar to the nature of "terroir" to the wine. I just got back from New Zealand and saw more than one winery advertising "Screw Top Free Zone". The perfection of a fault free bottle of wine every time has its attractions...but a few corked bottles here and there adds interest.

            Comment


            • #7
              Originally posted by Mike C. Miller:

              As I said, I have no idea if that amount is negligble or not, but the two ranges are not even in the same ballpark!
              The BEST (i.e. the ones that don't leak/let in too much air) are similar to the performance of screwcaps. That is the point of the post - that good corks perform in a similar range to screwcaps.

              GW

              Comment


              • #8
                Is this really an answer or is it one mans opinion? I know what I think.
                Andy Raffle

                Comment


                • #9
                  Originally posted by Mike C. Miller:
                  I don't have a dog in this fight, but I did take a statistics course once (well five of them, but who is counting).

                  Ignoring argument that the amounts of oxygen in question are de minimus for the moment, the numbers on the amount of oxygen allowed by the two closures are not even close. Taking the high end of each range, 0.1227mL is 153.375 times 0.008mL. Plus, did you say that each figure is per day? If so, the 150 times difference, cumulated over a number of years gets to be a very large difference, indeed. I don't think I have a calculator with that many zeros.

                  As I said, I have no idea if that amount is negligble or not, but the two ranges are not even in the same ballpark!
                  Yea, the numbers don;t seem close to me...
                  Andy Raffle

                  Comment


                  • #10
                    Tyson,

                    Why let legitimate, good science get in the way of a belief system?

                    Alex

                    PS In all seriousness, many thanks for the information ... I trust that with time and experience, the naysayers of screw caps will be converted!
                    I suffer from cellar envy ...

                    Comment


                    • #11
                      Case in point is one Andy Raffle -- never one is he to let good science stand in the way of his opinions!

                      Alex

                      PS Andy -- the Earth is round, not flat, buddy!
                      I suffer from cellar envy ...

                      Comment


                      • #12
                        [QUOTE]Originally posted by Jim Hills:
                        This is fascinating and in much more detail than I can ever comprehend. This enclosure will certainly gain increasing recognition and acceptance. One thing missing from the screwcap is similar to the nature of "terroir" to the wine. I just got back from New Zealand and saw more than one winery advertising "Screw Top Free Zone". The perfection of a fault free bottle of wine every time has its attractions...but a few corked bottles here and there adds interest. [/QUOTE

                        You find it interesting to spend good money, in some cases hunndreds of dollars, for a bottle of wine that's undrinkable because of a twenty cent cork failure? Not me man. I'm sure Russian Roulette is a real interesting game but I choose never to play. Bring on the screw caps.
                        Tyson thanks for the info. But the naysayers will never let facts get in the way of a romantic notion of cork.
                        Mitch Hersh



                        Life is not a dress rehersal.

                        Comment


                        • #13
                          Mike,
                          If the variance of the rate of ingress is 150 times per day between the closures, Isn't it so that the rate is also 150 times per week, per month or per year. You don't need to get a bigger calculator??

                          Comment


                          • #14
                            It is universally accepted that the greatest old wines are those with the best corks and the smallest ullages.

                            It's always made sense that that is so---and my own experience with ullage underscores it.

                            Comment


                            • #15
                              Well said, Tyson.

                              However, regardless of just how much solid, explained scientific logic you present, there will still be the "flat earth" thinkers who will choose to ignore it.

                              The study is the result of a substantial, objective and controlled experiment. The numbers don't lie. You can still not like the look or the idea of screwcaps, or object to their lack of romanticsm or break with tradition. The one thing that you can't hold against them is their suitability as a closure for the aging of quality wine.

                              Thank you for your voice of logic.


                              Cheers
                              Haskell Vineyards, Stellenbosch

                              Comment

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