Question For Comrade PhysioProf’s Readers

Why is an opened bottle of amontillado sherry that has been sitting on my counter for months with an EtOH concentration of 18.5% still perfectly good, while a bottle of Ridge zinfandel that is 15.9% EtOH spoils within a few days of opening? Is it that small difference in EtOH that makes the difference, or something else? And why does an opened bottle of fruit juice last for weeks in the refrigerator, but not wine?


  1. says

    Heat treatment.

    Fruit juice in your fridge is pasteurized, sherry is distilled to fortify it. Wine contains lots of compounds that are sensitive to oxygen that were removed by the heat processes that sherry and fruit juice went through.

    There are people who would argue that your sherry has degraded in flavor after being opened but it is certainly less than wine.

  2. says

    Is sherry distilled? I think it’s wine that has added spirits to “fortify” it (fortify its drinkers, more like). My guess would be that the sherry has been completely fermented, while your Zin still has some sugar in it. Why one is sensitive to oxidation and the other is not, I’m not sure.

    But thanks for giving me an Amontillado craving.

  3. George Smiley says

    Sherry is a fortified wine. I’d guess that the small difference in %EtOH may itself be significant (most fermenting yeasts, for example, stop growing at ~15%). In addition, the sherry probably contains less unfermented sugar than the Zin does.

  4. says

    First things first: Isis, me and CPP need to school you with some real serious Zin.

    Hmmmmmm…I tend to defer most to Cat as she is a bonafide food scientist.

    Bottom line: are we talking about oxidation or bacteral/fungal contamination?

    I submit that the % alcohol matters little in this comparison but rather what one considers “off” in each case. Moreover, are you tasting the results of true bacterial/fungal contamination or are you tasting the oxidation products of the zin?

    Sherries are already highly oxidized and if anything, have more residual sugar than a Ridge Zin. The combination of high alcohol (from fortification) and osmotic pressure from the sugar combine to prevent any further “spoiling” of the beverage. However, the “spoiled” nature of wine is exactly what we look for in sherry, amontillado, tawny ports, etc.: that warming, nutty, soothing, mouthfilling flavor.

    We expect red wines to have a certain amount of fruity character, even at 16% EtOH, but they’ll still oxidize even if the EtOH is too high to permit bacterial growth.

    I made a wine back in 1992 that still kicked total and complete ass when we drank the last bottle in 2005. However, I had a half fill of a bottle of the same stuff that within a month began to taste like a tawny port.

    What you have, Brother Phys, is a case of expectations. Amontillado is already near maximally oxidized. Even if your Zin was the same exact % EtOH, the fresh red flavors would still oxidize to a flavor reminiscent of amontillado, unless you got some Acetobacter in there that drove things toward acetate.

    WRT fruit juice, the vitamin C alone in these juices prevents oxidation. I was blown away by just how potent ascorbate was as an antioxidant when using it as a control in a DPPH assay (2,2-diphenyl-1-picrylhydrazyl, not Don’t Post Porn Here). Even with their sugar, most fruit juices have enough antioxidant activity to taste great until the sugars begin to be fermented. For example, apple juice goes “bad” first by oxidation, then later by fermentation, at which time we sell it at a premium as cider.

    It is now Saturday evening near 10 pm in my time zone and I shall now take leave for another glass of wine. To my dear colleagues assembled, happy thinking about the science of fermented beverages!

  5. juniorprof says

    BM….or I’m full of shite.
    Does anyone else find this profoundly funny, in a Naked Gun, Airplane kind of way?

  6. says

    Zin with 16% EtOH? Wow. I didn’t know Night Train was a Zin. Either that or you need to stop spiking it with Old Spice.
    Interesting thoughts, though I don’t know what to make of them….a hat, a brooch, maybe a pterodactyl…? Seriously though, would that account for the vinegar-ization of a reg wine after it sits out for a coupla days? Does sherry have a vinegarish tinge to it (I’ve never had sherry)?
    You owe me a new keyboard; you gave me a drinking problem. And I’ll never be able look at Sun Dappled Forest again without thinking of Macho Grande. So you owe me something for that too.
    I agree that CPP probably picked the wrong week to quit Jameson.

    As to the people who are still looking for the answer for CPP’s original question, I just stopped by to say, “Good luck. We’re all counting on you.”

  7. says

    Seriously though, would that account for the vinegar-ization of a reg wine after it sits out for a coupla days?

    Acetic acid bacteria would do the trick, I’d imagine.

  8. bikemonkey says

    Pop culture references go right by CPP in case anyone was wondering. Drives him craaaaazeeee. Hmm, hope sol doesn’t read this blog…

  9. Physiogroupie IV says

    Obviously, God wants you to finish the Ridge Zinfandel in a day.

    I agree with LostMarbles about different types of microbes and their penchant for different types of drinks (juice vs wine).

  10. says

    Sherry is distilled so that is why I said it had been heat treated.

    To answer Abel’s question about whether the reaction is oxidation or microbial spoilage. With most alcoholic beverages damage is caused by oxidation of the phenolic compounds. Alcohol is an inhibitor to microbial growth, especially at that content. Most yeast fermentations finish because the yeast has been killed by its own end product.

    As Abel said, with fruit juices oxidation will occur first and then yeast can grow. BTW, while ascorbic acid is a great antioxidant, it is also an amazing oxidant degrading quickly once exposed to air. You should try it in an oxygen meter. Ascorbic acid also degrades without oxygen being present so manufacturers add extra before bottling/tetrabrixing (it is a word now) so that the label is correct at the time of purchase.

    CPP you don’t say what year you had; younger wines go off quickly due to oxidation of phenolics. For example, the shelf-life of a Beaujolais Nouveau is probably less than a month even in an unopened bottle (released to be drunk on Nov; out of the stores by Christmas).

  11. says

    I feel the need to cast a further vote for the Zinophiles here – and for Ridge especially (although I confess that if my wallet were being crowbarred I’d go for a Shafer Merlot, which is a Merlot that they somehow get to have the complexity and depth of good Zin).

    The basic point has been made, though: just drink the rest of the wine :).

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