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  • #16
    Afterthought for Graeme.
    For the cork bottle to work, you will have to find some way of keeping the cork compressed. When cork is compressed, the oxygen in the cells is at a higher pressure than in the atmosphere, and this is why wine corks exclude oxygen ingress.
    Although this explanation is not quite as "revolutionary" as the heliocentric theory, it does seem to defy 'common sense'
    Just remember.
    They all laughed at Aristarchus
    When he said the sun goes round the earth,
    And Galileo too,
    Had an adverse peer review.
    John Casey<br />?

    Comment


    • #17
      John,

      While I can't discount your research and the effect of head space pressure and bottling process on subsequent oxidation, to downplay corks role in the resulting quality of an aged wine if fruitless against anyone with much experience of wine.

      Leaky bottles and lower than expected fill levels are directly attributed to cork failibilies (even if the bottle itself or storage issues have exhaberbated the problem), and most if not all will find it directly correlated to sub-standard and oxidised wine.

      I have many examples; Pesquera have had terrible corks in the past which leak all over the place. The variation in the maturities/state of the wine has lead me to return whole purchases.

      One bad batch of corks was experienced by me with Wynns Coonawarra Riesling. One bottle was put in the fridge but subsquently withdrawn to cellar. The wine bubbled through the cork. Then I saw more leakage on other bottles, dramatic colour variation, and based on the darkest bottle which was oxidised, returned the whole lot.

      Your research can in now way refute the fact that when corks leak, expecially obviously, they adversely effect wine.

      We can argue the % blame between bottling and cork, but that's as much as I can possible concede based on experience.
      Cheers, Nick. "It is only the dullness of the eye that makes any two things seem alike." - Walter Pater

      Comment


      • #18
        >We can argue the % blame between bottling and cork, but that's as much as I can possible concede based on experience.<

        That would be my view as well.

        Comment


        • #19
          Nick,
          For a wine bottle to "leak", the pressure on the inside must exceed the sealing pressure of the cork, "Water does not run uphill". This pressure is usually the residual pressure from the insertion of the cork, plus any additional pressure from dissolved gases in the wine and expansion of the wine with temperature increase. If the wine is in contact with the cork the headspace pressure increases the uptake of liquid vapour by the cork, which in turn softens the cork and reduces its sealing pressure. Virtually all "leaky" bottles I have ever seen had soft, sometimes soggy, corks, a result of excessive headspace pressure. As the headspace gas is usually air, excessive heads[ace pressure means extra air and extra oxidation.
          While wine bottlers bottle cold wine,have inconsistent, ineffective or inconsistent application of vacuum and lay the bottles down soon after corking, a certain percentage of the bottle will vent the excess pressure, (or "leak"), and the corks prematurely become soft.
          I kept records of cork performance for several years, and they showed that
          "leakage" was not related to price, grade or source, but was related to the increase in cork weight, which was later shown to be the result of excessive headspace pressure. Trust me on this one.
          Regards,
          John
          John Casey<br />?

          Comment


          • #20
            John,
            From your claims I take it you are suggesting that wineries are bottling with incorrect headspace pressures. Why is this?
            Do they not check this measure?

            I thought that corking machines are supposed to pull a vacuum such that pressure inside and outside the bottle is similar?
            And if wineries do not check this measure, and there is a significant differential, then why aren't all bottles leaking? Why is the nature of severe oxidation so random (I find fewer bottles suffering advanced oxidation than I do with TCA).

            How are we supposed to believe that with a measure as apparently critical as this, wineries - big multinationals with huge investments in packaging equipment - have such an inconsistent set-up on their equipment?

            I might add, as a final point, that if the whole cork/bottle seal/headspace pressure question is so fraught with peril as you seem to think, then clearly our method of 'internally sealing' a wine bottle is intrinsically flawed. Like trying to win a Formula 1 race with a 1930s sidevalve engine! "Can we build the engine from lighter materials? Can we improve the carburettor? Make the exhaust faster flowing?" Can't make a silk purse from a sow's ear, you know...

            cheers,
            Graeme

            If your claims are right, then why aren't most bottles oxidised to a detectable threshhold?

            Comment


            • #21
              Graeme,
              No, wineries get it right most of the time, but the application of vacuum at the corker is not always effective and consistent; it requires constant monitoring. The same applies to air contact during handling and filling. There are quite a number of "critical control points", and like any other industrial operation where there is a dilution of skills, some companies do a better job than others. I could be repeating myself when I say, that all the "leaky" and/or oxidised bottles that I have examined had two things in common, viz., residual pressure and increase in cork weight of a gram or more, and most of the 'oxidised bottles had reduced CO2 content, indicating pre-bottling contact with air.
              I know that it seems obvious that the cork is the problem, but in fact it is just the scapegoat.
              Regards,
              John
              John Casey<br />?

              Comment

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