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Jan 9, 2007 01:17 PM

Strange Substance on the cork?

I opened a bottle of red wine last night and found a dark red/black grainy gunk all over the bottom of the cork and around the neck of the bottle. It looked sort of crystalized on the bottom of the cork, like black salt crystals. The wine tasted like it had been open for 3 days...just flat and gross, but no "off" or rotten flavor or aroma. What happened? I assume the cork was letting air in or something to oxidize the wine...but what was the gunk? Is this what is meant by a "corked" wine or is this something elese?

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  1. Tartrates.

    Wine is a super-saturated solution of tartaric acid. You have crystals of tartaric acid, or tartrates.

    In white wines, tartrate crystals are usually found (if at all) at the bottom of the bottle; in red wines, they are found (if at all) adhered to the cork. The dark color comes from the color of the wine itself.

    It is precisely for questions/concerns such as ours that most wines produced in the New World, as well as many from Europe, are COLD STABILIZED. Cold stabilization involves lowering the temperature to a point lower than it has ever been before -- think colder than a home or commercial kitchen's refrigerator or ice bucket will get -- and get the crystals to form and precipitate out while the is still in tank, prior to bottling. That way, when your bottle gets chilled -- either in one's cellar, in transit, in the refrigerator, etc. -- the crystals won't form inside the bottle and people won't ask, "what are these crystals in my wine?"

    Becasue tartaric acid is the major acid found in wine, having thecrystals drop out in the bottle will result is a wine with lower acidity and thus (perhaps) the wine will taste "flat," but it does NOT affect flavor, only the balance of the wine.

    "Corked" gererally refers to a wine infected with 2,4,6-trichloranisole (TCA) and has nothing to do with tartaric acidity, tartrate crystals or any other naturally occuring, normal process.

    1. No, that is not "corked" wine. That term refers to an interaction between the wine and usually chlorine, used to disinfect the cork, though could be caused by such contamination, as wood perservative used in the barrel-house. During this interaction, several things seem to happen - the "fruit" components in the wine diminish, the acid level of the wine elevates, and a "musty/wet newspaper" aroma develops. This is from the TCA that forms.

      What you most likely encountered was the natural process of suspended solids in the wine dropping out. This is natural in many, many red wines. When certain molecules bind, they become too heavy to stay suspended. One term for these solids is "lees." The "crystal" aspect of this sediment is likely tartaric acid crystals (very common in white wine, that has see a low temp at some point in its life), and they also percipitated out. Having this sediment in the bottle neck and attached to the underside of the cork indicate that the bottle was most likely stored on its side for a long period. This type of storage is recommended, as it lets the percipitates form on one side of the bottle and also keeps the cork moist, helping it form a better seal.

      No aspect of this "find" indicate any problem, and cannot account for the flatness and grossness, that you encountered. Was there any trace of wine at the exterior top of the cork? Anything under the capsule? Any stains on the label? The cork could have leaked too much oxygen, but not have leaked enough to allow any liquid to escape. What was the wine, the age and what colors did you notice, when poured? Was is dark to the rim, or did it reveal a brownish tinge? While signs, common in an older red, they could indicate premature "aging," or oxidation in a younger red. Your description of the wine tasting like it had been opened three days, is a good way to describe oxidation - only the sediment does not, of itself, indicate that.

      A side note: as red wines throw their sediment, if it is allowed to accumulate on one side of the bottle (a reason for NOT rotating your wines in the rack), standing it upright for a day, or two, will allow the loose sediment to fall to the bottom of the bottle. When one decants the wine, to separate the clear wine from the sediment, prior to drinking, it is usually easier to pour with the attached sediment sticking fast, and the loose sediment at the bottom. This sediment, when re-suspended in the wine will often impart a bitter note to the wine. This sediment and the need to separate it from the wine, is one reason for the sharper shoulder on a Cab, Merlot, Zin, Bdx. bottle. Much is now "tradition," regarding bottle shape, but there is a reason for some parts of its design.

      Doesn't answer WHY your bottle was flat, but the "gunk" didn't do it.


      2 Replies
      1. re: Bill Hunt

        Wow, Thank you for the very imformative and interesting replies. As for my was a 2003 Belvedere Healdsberg Merlot. We had tasted it in the store and it tasted nothing like it did when we opened that bottle ( tasted much better than when we opened that bottle anyway, there was some resemblance). There was nothing on the exterior of the bottle to indicate that something was wrong, no staining or other signs of leaking. I don't remember the color having a brownish tinge...but that doesn't mean it didn't, just means I wasn't looking for it, so I don't remember.

        I've got two more bottles of this one in my cabinet, so we'll see how those come out. But good to know for future reference, since the sediment in the neck of the botttle was a first for us. So for future just stand the bottle up and let it settle to the bottom and it should be fine? (since the flat taste wasn't related to the sediment)

        1. re: wawajb

          Well, standing the bottle will help settle most of the sediment, that is not attached to the bottle side/neck, and make it easier to decant to separate the sediment from the clear wine. Whether it will make it taste "better," is up to you.

          You may have encountered "bottle variation," and this happens for a number of reasons. It is often obvious, when one is opening several bottles of the same wine, and tasting each, say before a dinner, or event. Winemaking is part art, part science, part history, and part luck. Sometimes the "luck" runs out on a particular bottle.

          As for decanting, there are three reasons to do so:

          1.) to aerate the wine (red OR white) to simulate aging a bit. This is often referred to as "caraffing" the wine.
          2.) to separate the sediment from the clear wine.
          Note: 1 & 2 often go hand-n-hand, but not always.
          3.) to get the wine out of the bottle, that it came in. This is usually because you do not want "Uncle Louie" to see that he's drinking 2$Chuck! BTW - hide the bottle, if you do #3! Uncle Louie might poke around the trash can, looking for a clue...

          Back to your Merlot for a moment. Merlot, like many reds, has a tendency to throw sediment, though your's wasn't THAT old. Time will allow more sediment to develop. This is a natural occurrance with aging many reds. The amount of sediment that you describe is a bit puzzling to me. Some winemakers use less filtering and less "fining" of their wines, so that more of the "character" of the varietal comes through - at least that is their plan. I do not know this wine, so I do not know what techniques might have come into play. Please report to this thread, when you do taste the others. I hope that they are more like the one, that you remember.


      2. As an aside, it was tartaric acid crystals taken from lees that Louis Pasteur was examining when he discovered that there were two mirror-image forms of the crystals, and [somewhat later] of other compounds that are otherwise chemically indistinguishable - a discovery which led to the science of what we now refer to as stereochemistry.

        1. Since the wine is so young, it is possible that it was shipped in the cold months and that the wine got too cold, therefore, allowing the tartrate crystals to form.

          1. "gross and flat" could describe a wine subjected to temperature extremes. Tartrates on the cork point toward cold, if the wine was cold stabilised to 0°C. And hours above 30°C would mute and fruit and stimulate sulfur compound formations.