How Late is Early? Thoughts on Premature Oxidation

The business of very fine wine happens in a rarefied atmosphere, so it’s ironic that one of the most highly discussed issues concerning wines’ cellar worthiness concerns oxygen—specifically, premature oxidation.

Wine aging is essentially a slow process of oxidation, but the thought that some of the world’s most expensive and collectible wines might age prematurely is worrisome. Collectors and passionate tasters want to lay the wines down for decades, whether for enjoyment or resale value, and rightly flinch at the prospect of their investment being rendered worthless.

The Pox Plague

The issue of “premox” (or even “pox,” its other nickname) first came to the fore at the turn of this century, when bottles of highly valued white Burgundies from the mid-1990s showed up dead on opening. They exhibited dark color, with their fruit aromas gone and none of the zip and freshness that Chardonnays from Bourgogne are known for—even though they were barely a few years old. The problem generated a lot of research and discussion, and although no single clear and definite cause has been identified, certain issues related to bottling, as well as certain aspects vineyard management, have been fingered as likely culprits.

Organizations like the Bureau Interprofessionnel des Vins de Bourgogne (BIVB) have provided producers with guidelines to help counter the problem, which seems to be lessening in the region. In an interview with Vitisphère (subscription only), BIVB technical commission vice president Géraud-Pierre Aussendou reported a much lower occurrence thanks to greater awareness and changes in winemaking choices, notably picking earlier to preserve acidity.


The Red Menace

RedBordeuxStill, similar questions have been raised about white wines from regions like California and Australia. And in the last few months, concerns about premature oxidation have been revived in recent articles stating that the problem could happen in high-end red wines as well. Reporting on a study from Bordeaux researcher Denis Dubourdieu and his colleagues Valérie Lavigne and Alexandre Pons, Jane Anson wrote in Decanter that the lack of stamina of high-end wines is an impending wine crisis:

“There were plenty of rumblings about this at a recent ten-years-on tasting of Bordeaux classed growths from the 2003 vintage. Even among the biggest names there were bottles that were showing tired fruit, flabby structure, and were generally past their prime; all signs of oxidative destruction that is not expected at such an early stage in the life cycle of fine red wine.”

The likely culprits, as pointed out by Douburdieu, are overripe grapes with high pH, excessive contact with oxygen at an early stage in winemaking, high amounts of new oak, and lower SO2 levels. While all of these choices are made with good intentions—and for pleasing certain influential critics who liked the bigger, bolder, friendlier style—this combination can potentially reduce the wines’ resistance to oxygen and thus their capacity for aging.

Of course, as Anson recognizes in her article, the 2003 Bordeaux vintage is a bit of an extreme example. A summer of excessive heat, unseen before or since, caused sugars to rise and acids to drop at an unprecedented rate there and in many other European wine growing regions. Looking for both ripeness and balance was a difficult challenge that year, and no one expected such a sun-baked vintage to provide the best aging potential, even early on. In that sense, is it really so surprising that wines made in such extreme and unusual conditions are showing a bit of fatigue at 10 (and now 12) years old?

Dubourdieu and his colleagues, however, insist that if subjected to certain practices, wines from all hot and ripe vintages (like 2009, for example) could be at risk. Many issues are likely at play, but in wines with higher pH—especially nearing a pH of 4—SO2’s protective capacity against oxidation is greatly diminished. This in turn accelerates the chain reactions that lead to stewed fruit and dried fruit characters, as well as a loss of color and other characteristics of aged wines.

Random vs. Uniform

While the question of a wine’s aging potential—and how vineyard practices and winemaking techniques may affect it—is a fascinating subject, it seems a somewhat distinct question from the original premox crisis of the mid-1990s. Those premox issues in Burgundy were characterized by the random appearance of highly-oxidized bottles within a same lot, meaning that while some bottles showed up stewed and old, others were crisp and fine. The issues raised by Dubourdieu and his colleagues, however, point to a tendency for all wines from hot vintages, or at least those made in a very ripe, low-acid style, to age faster than expected, meaning over several years rather than over a few decades.

While the two issues do have some common characteristics—in both cases, high pH is a big part of the problem, for instance—there are clearly some different mechanisms at work. In the case of white Burgundy, the question largely has to do with uniformity and homogeneity. In the case of red Bordeaux and other big, cellar worthy red wines, the issue seems to have more to do with wine growing and winemaking choices.

Regardless, both issues are certainly worth looking at carefully in terms of oxygen management, and we will return to them in further posts to address the various elements at play.

Photo credit: Imgkid and Wine Enthusiast.

About the Author

Rémy Charest is a Quebec City-based journalist, writer, and translator. He has been writing about wine and food since 1997 in various Canadian and American print and online publications, includijng Le Devoir, Le Soleil, Coup de Pouce, EnRoute, Palate Press, Punch Drink, WineAlign and Châtelaine, and has been a regular radio columnist for Montreal's CJAD and CBC/Radio-Canada. He is additionally a wine judge for national and international wine competitions, notably the National Wine Awards of Canada and the World Wine Awards of Canada organized by WineAlign.

Rémy Charest Photo Credit: Jason Dziver


  1. You don’t say anything about the cork, perhaps the real reason for Pox. Testing by the manufacturers of the newest style of technical corks show a wide variation in the oxygen transfer by cork of the same quality and brand in the same bottling run. It looks like corks can be unpredictable. I am still a believer in the use of natural cork but I am beginning to doubt my loyalty after seeing some of these test results. While it is unlikely a cork problem if the whole run shows Pox do we know that this is actually the case or has the experience been with a few bottles. Here in Sonoma we make wines from grapes that are typically riper, lower in acid and higher in pH than do most wineries in France. At Deerfield we bottle wine with lower SO2 than do most wineries anywhere. We have experienced Pox in only isolated bottles, not entire runs. This is not just in young wines but wines aged as long as are the typical French wines, red and white.

    1. There is an upcoming article on premox that will look more closely at the issues related to bottling and corks, and indeed, they are a factor in variable levels of oxidation in the same bottling runs. Figures studied by Nomacorc have shown a significant level of variability between natural corks of a same batch, as well – and offering greater consistency is one of the reasons for being of Nomacorc and other technical cork producers. You’ll find interesting data on variability in corks and in various bottles in this video from a Wine Science Forum held in Napa in February 2014, at the beginning of a bottling study whose results are just being released now.

  2. In today’s big power reds, there is no question that overripeness and field oxidation is the chief culprit. When the oxygen appetite of such wines is measured, they consume much less rapidly, and thus are prone to oxidation.

    However, in healthy wines of proper ripeness, skilled application of small amounts of enological oxygen can be used to dramatically increase longevity by stabilizing short chain polymers and fixing color. Oxygen is not itself the culprit, but rather the lack of skill.

    Similarly, high pH is a more nuanced business. Since red wine pigments bind essentially all SO2, the molecular form is not really present at any pH. What protects red wines is their oxygen appetite. Phenolic oxygen uptake is driven by the high pH phenolate form, which is more active at higher pHs. In overripe grapes, the phenolic reaction has already occurred, so insufficient phenolate is left in the reactive monomeric form. But healthy reds protect themselves better at modestly high pH (in the range of 3.7 to 3.85) than they do at pHs below 3.6.

    The focus on SO2 is a red herring for another reason. Contrary to the statement of your article, SO2 has no protective capacity against oxidation. The sulfite form (SO3–) is a high pH form in such small quantities that its direct reactivity with oxygen, although faster at high pH, may be discounted even there. What decreases at high pH is its inhibition to microbes in white wines. The situation in reds is quite different.

    Free SO2 inhibits phenolic uptake by reacting with quinonal intermediates and short circuiting the polymerization reactions that take up oxygen. Said more simply, SO2 decreases the ability for red wines to take up oxygen by an order of magnitude or more, and is itself totally ineffective against spoilage organisms such as Acetobacter.

    Coming back to the original cause, I agree that it is quite distinct from premox in white burgundies. The makers of great reds have always felt a duty to make wines with longevity potential. Many California winemakers in the tonier appellations have consciously abandoned this duty in favor of wines that please upon release.

    In our rapidly expanding market, sales are driven by well-healed novices looking for fruitiness and impact. I call these “clown wines.” There are plenty of Napa producers who not only hang their fruit to 29 brix, but then add high proof and sugar.

    The only mystery is how long consumers will continue to reward these shameful practices.

    1. Thanks for the comment, Clark, all sorts of fascinating and complex principles in there. I’m not sure I entirely agree with the way some of your statements on SO2 are formulated, and discussions I’ve had with other researchers (like Dominik Durner and Nicolas Vivas) on questions linked to phenolics, polymerization and oxidation would lead me to slightly different conclusions, notably on pH. There are a lot of nuances to be made – and it’s normal that such complex chemistry would still be a matter of debate on certain levels.

      I’m glad we agree that the term premature oxidation is used in two very different contexts, here, and it’s something I’ll be talking about further in two more blog posts to be published here in July.

      Part of this whole question centers around winemaking objectives – and wine-drinking goals. I’m not sure long-term aging potential is necessarily the ultimate goal in winemaking, for instance – although collectors of Bordeaux would disagree with me, I’m sure. A problem does arise, however, if one is promised something (“this will age for decades”) and the wine doesn’t deliver.

  3. Exactly so. Certainly in many wines (e.g. NZ Sauvignon Blanc or Nouveau Beaujolais), there is no expectation of longevity. Some wines (dry roses and Brouilly, for example) age much better than consumers expect. But clearly, the purchase of a classified red Bordeaux or a Napa Cabernet Sauvignon priced over $100 includes an implicit guarantee of age-worthiness and an invitation to cellar.

    Perhaps offline you’d like me to show you the support for the positions I’ve taken above. I’d love to hook in Nicholas Vivas, for whom I have the greatest respect. I doubt we will have much trouble reaching consensus. Nicolas was present at the 1999 Demptos conference in Bordeaux where Aline Lonvaud-Funel presented her too-little-read research on the ineffectiveness of pigment-bound SO2 on Acetobacter.

    It is somewhat unrealistic to call for even avid and intelligent non-winemakers such as your readership contains to delve so deeply into these complex nuances, but a respect for the complexities is essential when they are tempted to seize the wheel and tell winemakers how to proceed, what tools to use and what numbers to look at.

    On the other hand, only a consumer outcry can put an end to the intentional trashing of the reputations of places like Napa Valley. Articles like your latest above are essential, and I do believe that the public hue and cry has led Burgundians to think twice about ripeness and about the technical aspects of pH, oxygen, bottling practices and so forth.

    I question the tactic of co-opting the term premox to embrace the more recent problem with reds, only to conclude that the two are unrelated. If we are to enroll consumers in the fight against clown wines, we ought not to mire their attention with details of performance when the real enemy is economic. They make those wines to make money, and because our American market is growing, there is always a fresh supply of newbies to fleece.

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