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  • Question for Matk and surviving panelists

    Question re "random oxidation" for Mark and surviving panel members.
    WHY?
    There is a simple, plausible and scientific explanation for "random oxidation" which is supported by published data. It is caused by the relatively slow oxidative effects of oxygen and oxidants in the bottle at sealing. The usual methods of sealing the bottle have little or no effect.
    After ten years research, there is still no credible evidence that "residual oxidants" in the cork or the ingress of atmospheric oxygen through the cork play any role in post-bottling oxidation. Moreover, both these hypotheses are demonstrably false.
    "Breathing corks" is a little bit of 19th century obscurantism which still has some winemakers in its thrall. The question is: Why is it still being promoted?
    HINT. The answer must lie outside the realms of the physical sciences.
    John Casey<br />?

  • #2
    If by Mark you mean me--- I cheerfully concede total ignorance on chemistry. :smile:

    Comment


    • #3
      It seems to be a common urge to supply simple, plausible explanations for complex phenomena. Simple, plausible and wrong. I struggle to with numerous aspects of your theory. What do varying levels of ullage in older, well-cellared bottles say about the permeability of cork?

      I accept that on modern filling machines different nozzles will behave differently with regard to oxygen ingress - Michael B. confirmed as much. But to attribute the random oxidation typically encountered by wine-lovers to this seems disingenuous to me. If a filler nozzle on a 10-unit machine was incorrectly calibrated, would we not expect to find fully 10% of the resulting wine suffering such a defect?

      Moreoever, I have occasionally tasted wines quite young (and dark - I'm thinking of a 96 Leeuwin Estate Art Chardonnay tasted in 2000)) suffering advanced oxidation, for which the only logical explanation is a faulty cork.

      Whe you refer to "After ten years research, there is still no credible evidence that "residual oxidants" in the cork or the ingress of atmospheric oxygen through the cork play any role in post-bottling oxidation" are you referring to what we would call 'bottle development', or catastrophic oxidation which renders a wine a shadow of its potential? I understand the contention of the screwcap proponents to be that your statement is what everyone would wish to see - ie. corks impervious to oxygen, but that in reality it is the random nature of oxidation caused by the passage of air through 'faulty' corks which is responsible for spoilage.

      I agree that there is a very widespread view that some slight exchange of air is necessary for proper aging - an incorrect view, but one which, ironically, pinpoints the reason for the frustratingly inconsistent performance of older bottles of wine, even those which have a shared cellaring history.

      Do you have more specific details of the research you have cited?

      cheers,
      Graeme

      Comment


      • #4
        I used to believe that ideal aging occurred with perfectly functioning corks and no oxygen ingress into the bottle. After reading all the postings in this forum, I'm beginning to wonder if, as Graeme put it "the random nature of oxidation caused by the passage of air through 'faulty' corks which is responsible for spoilage" is also responsible for some of the characteristics we cherish as secondary and tertiary characteristics in some of those magical bottles of older red wines.

        [ July 02, 2003, 12:52 AM: Message edited by: David Glasser ]

        Comment


        • #5
          Originally posted by David Glasser:
          ...responsible for some of the characteristics we cherish as secondary and tertiary characteristics in some of those magical bottles of older red wines.
          David, as these are invariably the bottles with the best ullage levels, I'm still inclined to think these are the bottles where the cork has fulfilled it's job as the perfect seal, permitting virtually no oxygen through - the same things that modern screwcaps are intended to achieve.

          There have been several detailed accounts on this forum of old-screwcap tastings - I suspect any bottle variation between old screw-caps is indeed caused at the bottling line as John suggested above...

          cheers,
          Graeme

          Comment


          • #6
            When starting to read this thread, I became confused by the term random oxydation. I suppose you mean the number of faulty corks that permit Oxygen to diffuse through them is random. Obviously the chemical reaction is not random.

            Someone mentioned ullage. I have often wondered about how water and alcohol can diffuse through the cork and not Oxygen. Obviously if the former can do it so can the latter.
            I have heard experts say that all of the transfer is between the cork and the glass.

            Every Oenology textbook that I have read says that bottle-aging is a reductive process. Of course that assumes a good seal with a cork.

            [ July 02, 2003, 10:58 AM: Message edited by: Howard Sherry ]
            Howard

            Comment


            • #7
              Originally posted by Graeme Gee:
              </font><blockquote>quote:</font><hr />Originally posted by David Glasser:
              ...responsible for some of the characteristics we cherish as secondary and tertiary characteristics in some of those magical bottles of older red wines.
              David, as these are invariably the bottles with the best ullage levels... </font>[/QUOTE]Sorry, Graeme, but the great bottles are not invariably the ones with little or no ullage. The odds are undoubtedly better with less ullage, but I've had exceptions, and I've seen more experienced palates than mine post exceptions.

              Howard - my point is that, having read so many posts about how variable corks are in their ability to exclude, perhaps I need to rethink my unquestioning acceptance of the common wisdom that aging is reductive. Or maybe I just like spoiled wines...

              I'd love to see reports on a variety of different red wines, particularly Cab and Cab-based blends, kept under screwcap for at least 10-20 years, and from a variety of tasters.

              Comment


              • #8
                OK, "invariably" was a bad choice of words. It is, as you say, most often the case, but it's not guaranteed. I was, however, picturing a situation where, for example, 5 bottles of 59 Latour are extracted from a cellar where they've been resting peacefully for 40 years. If 1 bottle is just into the neck, 2 are very high shoulder, two are high shoulder, I know which one I'd bet on to taste in the best condition!

                cheers,
                Graeme

                Comment


                • #9
                  Mark Squires
                  Yes, I did mean Mark Squires, whom I thought was the one and only, the alpha Mark.
                  Rest assured Mark, the chemistry is impeccable, and the question is a non-technical one.
                  It does raise another question. If the pundits can be so wrong about ‘post-bottling oxidation’, how credible are their pronouncements on other matters relating to corks?

                  Graeme
                  I’ll take it from the top, Mencken notwithstanding. The item was a follow up from a more explicit comment in the posting “Permeability of wine corks”
                  .
                  Varying wine levels in old bottles mean differences in initial headspace pressures, the pressures being sufficient either before or after a temperature rise to expel some wine from the bottles. Excessive pressure, like hypertension in humans, causes tissue damage. The corks from these bottles are usually softened by condensed liquid vapour.

                  The major source of oxygen and oxidants is air contact in the handling and the delivery of the wine to the filler, (further details near end of posting.“Role of oxidation”). This is often sporadic and transitory. Significant pick up at the filler can occur in the filling bowl during stoppages, but most other sources of oxygen are relatively minor, apart from their being cumulative.

                  Naturally, I can’t say categorically what the problem is with the Chardonnay you tasted, but I am willing to wager my irreplaceable possessions that the problem has been sporadic air contact before or during bottling and if the corks are soft, the problem has been aggravated by headspace pressure. We have ways of testing this hypothesis.

                  I am referring to unacceptable oxidation in bottled wine ranging from just noticeable to catastrophic. The contention of “the screw cap proponents” [sic] is incorrect. In the immortal words of Mandy Rice-Davies, “Well they would say that, wouldn’t they?” The error is based on a misunderstanding of the nature of the oxygen barrier mechanism of a wine cork as opposed to its manifest permeability to gases and vapours; the two are not the same. I can say emphatically that sporadic, post-bottling oxidation or PBO, (sometimes call “random oxidation”) has nothing to do with cork. According to the UK Wine& Spirit survey of some 12,000 retail wines, PBO occurred at around 1% of wines sealed with cork and with synthetic stoppers. I know from very long, personal experience that it can and does occur in bottles sealed with metal caps. In fact, there was such a problem in Australia some nine months ago..

                  References. DeRosa & Moret, Leske et al, and Godden et al. Can I e-mail the exact references? I also have a brief article in a forthcoming issue of the Aust. NZ Grapegrower & Winemaker.

                  David Glasser.
                  Yes, and Yes.
                  I’m afraid that catastrophic oxidation is the ultimate destiny of all of us, and I am probably more oxidised than you are. Even the glass in light bulbs admits minute amounts of oxygen when hot for prolonged periods. Keeping oxygen out of a sealable container is like trying to keep dust out of a house on an unsealed road. In the long term, small amounts of oxygen will alter the character of the wine without overt spoilage, red wines being more resistant than white wines because of their higher phenolic content.

                  Howard Sherry
                  “Random oxidation” is a silly term as it seems to imply the outcome of unknown inscrutable factors. I prefer ‘(sporadic) post-bottling oxidation’ or PBO, and I contend that it has nothing to do with the cork. As Shakespeare is alleged to have written, “. . . the fault, dear Brutus, lies not in our corks, but in our handling and bottling operations.”
                  “Random oxidation” is a pseudo-phenomenon which was invented in Australia about ten years ago to lay the responsibility for bottling problems on the cork suppliers. I cringe when I hear references to this absurd bit of ‘good old Antipodean know-how’
                  John Casey<br />?

                  Comment


                  • #10
                    Originally posted by John Casey:


                    ;. . . the fault, dear Brutus, lies not in our corks, but in our handling and bottling operations.”
                    Great post John

                    Agree with your statements adding that post bottling storage of bottles at humidity levels below 70%, for example during transportation or sitting on distributors' shelves, is the single most important factor which will result in many disappointments down the development road.

                    Thus bottle variation, also but not only in terms of oxidation (randox) finds causes during bottling and is accentuated during sub-optimum storage.
                    everyone should believe in something - I believe I'll have another cigar - winetemplar
                    ....... .... ....°°°°°°o°oo°o°°O°O°°°0OOO
                    ITB - owner ARCave - building supplies manufacturer, prefab cellars ARCave.com

                    Comment


                    • #11
                      Originally posted by Graeme Gee:
                      OK, "invariably" was a bad choice of words. It is, as you say, most often the case, but it's not guaranteed. I was, however, picturing a situation where, for example, 5 bottles of 59 Latour are extracted from a cellar where they've been resting peacefully for 40 years. If 1 bottle is just into the neck, 2 are very high shoulder, two are high shoulder, I know which one I'd bet on to taste in the best condition!

                      cheers,
                      Graeme
                      I agree with you. David is right that there are exceptions to everything, but the exceptions prove the rule. I've done this experiment from case lots many times--the bottles with the best ullage have aged more gracefully and are in better condition almost every time. This makes intuitive good sense, and also it has followed on to be true in my actual tastings. There is a VERY high correlation between a good fill and a good bottle--all other things being equal--and that is especially so if the fill is poor on a rather young bottle in which case you can remember the robot on the Lost in Space show: "Danger! Danger!"

                      Messing around with poor fills, moreover, is a high risk endeavor. Certainly anything below base neck poses inherent risks. It is true that fills tend to decline with age, but when you see one 1953 Latour (I possess it...) with a fill well into the neck and another (I own that too...) with a fill 1/4 inch into the shoulder, you have to say the declines vary from bottle to bottle and are not inevitable. You also have to say, I think, that the decline has certain implications that are unavoidable, i.e., absent leakage, one cork is not doing its job as well.

                      >It does raise another question. If the pundits can be so wrong about ‘post-bottling oxidation’, how credible are their pronouncements on other matters relating to corks?<

                      Relatively little scientific attention has been paid to wine. People assume lots of things. They may be right. It may be good, common sense. But there isn't always much proof other than anecdotes and common wisdom.

                      Comment


                      • #12
                        Gosh John, let me see if I’ve got this right. Destructive oxidation is caused by careless handling in the winery, and on the bottling line. It’s caused by poor set-up of filling machines mixing in too much oxygen while trying to pull a vacuum to allow cork insertion. This results in bottle pressures that cause air to leak past the cork. It’s caused by poor storage and handling of wine resulting in a break in the seal between the bottle and cork, leading to oxidation of wine. But it’s NOTHING to do with the cork!

                        These systematic errors will frequently result in aged bottles tasting different to each other, despite them having identical handling and storage histories.

                        You haven’t mentioned anything about poor bottle finish inside the neck – there’s another source of seal failure causing oxidation. If only the wineries, bottling machines, storage facilties, & handling industries could live up to the standards achieved by the corks themselves, then we’d have no problem, right?

                        I’m beginning to think that the best solution is to store wine in hollow, 100% cork vessels. Bingo, problem solved!

                        Cheers,
                        Graeme

                        Comment


                        • #13
                          Graem, references pasted below
                          References
                          Casey, J.A. (1998) Sporadic oxidation of packaged wine. Australian Grapegrower &
                          Winemaker, 416; 37-39.
                          Casey, J. A. (2001) Venting or leaking? Residual headspace pressure in bottled wines. Australian
                          Grapegrower & Winemaker, 453; 115-118
                          De Rosa, T. & Moret, I. (1989) Influenza dell' imbottigliamento in ambiente di gas inerte sulla
                          conservazione di uno vino bianco. Revista di Viticultura e di Enologia, 5 219-226.
                          Godden, P., Francis, L., Field, J., Gishen, M., Coulter, A., Valente, P., Høj, P., & Robinson. E. (2001).
                          Wine bottle closures: physical characteristics and effect on composition and sensory
                          properties of a Semillon wine, 1 Performance up to 20 months post-bottling. Australian
                          Journal of Grape and Wine Research, Vol 7, No2.
                          Leske, P., Bruer, N., Davies, M. & Matthews, I. (1998). The effect of headspace treatment and bottle
                          storage orientation on wine quality - a preliminary study. Aust. NZ Wine Ind. J. 13(4), 430-434.
                          John Casey<br />?

                          Comment


                          • #14
                            Graeme
                            Are you putting me on:
                            I'll try again. The major cause of oxygen absortion in wine is air contact during handling.
                            Air contact shortly before filling results in the formation of oxidants and then more oxygen can be absorbed during delivery to the filler and in the filling operation These are not common occurrences, but then PBo is not all that common among the majority of wine companies. If the vacuum is not applied eggectivel and consistently, some of the bottles will pick up additional air as well as having elevated headspace pressures, (see the data of DeRosa et al). Surbeys of Retail bottles in Australia show that some 10-15% of retial bottles have had excessive headspace pressure.
                            See also My postings at "cork permeability" and "role of oxygen in the maturation of wine"
                            I know that it seems obnious that the problem is the corks, I used to think tha myself some 15 - 20 years ago.
                            The main problem with bottle bores is that "A bores" (flaring) make it difficult to extract the cork, while "V bores" tend to allow th cork to move out when the headspace pressure is high, Enlarged bores generallu decrease the sealing pressure slightly.
                            John Casey<br />?

                            Comment


                            • #15
                              Graeme,
                              I just picked up on a couple more of your points
                              The best way to avoid oxidation is to install in-line sight glasse on the outlet side of all delivery lines, and when you see any bubbles, stop immediately and find the air leak. "Relentless pursuit" was the motto at my former employer.

                              During filling operations, the filling bowl should be emptied at scheduled breaks, and if there are long unscheduled stoppages the wine in the filler is returned to the supply tank. Operation of the vacuum corker shoud be under constant scrutiny. and there need to be occasional checks on bottle pressure. Preventing oxidation of white wines is not easy in a terrestrial environment
                              John Casey<br />?

                              Comment

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