Premature Oxidation Of White Burgundy
An extract from My Favourite Burgundies by Clive Coates, to be published in mis-summer 2013
Some fifteen years ago it began to become apparent that some of what should have been the best premiers crus and others were not holding up as they should have been doing. Fine white Burgundy, after all, is the supreme dry white wine for aging. Anything half-way decent should be better at ten years rather than five. While one might be prepared to accept certain other chardonnays which were already aging at five years, if this occurred in a top Puligny or Meursault it just wouldn't do.
At first these bad bottles appeared merely to be some unfortunate one-offs. But as time went on reports began to circulate of more and more oxidized bottles, and from just about every single estate, even the very prestigious – Lafon, Bonneau du Martray, Roulot, Ramonet. No one seemed to be spared. It was rather like a very contagious plague.
I've had my own experiences. In Atlanta, at a dinner of the local Confrérie de Tastevin some years ago, we had to open a full case of Puligny-Montrachet, Les Combettes, from Domaine Etienne Sauzet, to obtain four decent bottles. Chez Ramonet, with a group, and Noël generous enough to offer a vertical of his Ruchottes, the two of us were holding bottles of the 1998 (or was it the 1997?) up to the light to find a wine with a clear youthful colour. In my cellar I had a dozen bottles of 1999 Puligny-Montrachet, Les Demoiselles, Domaine Colin Déleger. I tried three. All excessively oxidised before their time. Then I discovered that six of what I thought was twelve were in fact Chassange-Montrachet, En Remilly. No problem. But what do I do with the three remaining bottles of Demoiselles? I can't sell them. Happily, thankfully, these are the only off bottles in my cellar. But a story from Dominique Lafon. In April 2011 he found himself in a bistro in Burgundy. His meal was interrupted by a stentorian (American) pronouncement – 'Prematurely oxidized' – from the other side of the room. He looked up and saw that the wine was his. He called the wine waiter over. The wine was his basic Meursault 2004. He tasted it. Not a bit brilliant. And now aged. But not 'prem-ox'. Just a bit old. He went over to the American table. This is my wine, he said. And the wine is getting old (and it was by no means a great vintage), but it is what I would expect it to be after seven years. Obviously you prefer your wines younger and fresher. Please accept a bottle (nod to the wine waiter) of my Clos de la Barre 2008 with my compliments. The moral here: not all so-called 'prem-ox' bottles are prematurely oxidized.
Naturally, alongside the evidence of oxidized bottles came the theories. Why had this happened? Why had there been no previous warning? What, indeed were growers doing today that they had not been doing pre-1995, the vintage when all the problems seemed to begin?
The first culprit was the cork. We are all agreed that the standard of cork supply has dropped. The bark was being stripped to soon. The stripping was occurring too near the base of the trunk. No one, it was pointed out, had experienced a prematurely oxidised screw-top bottled white Burgundy. Moreover, those who wax the ends of their bottles, like Raveneau in Chablis, seem to have less bad bottles. While the incidence of bad bottles at Roulot and Lafon, in my experience and theirs (and I believe them) was confined to one or two isolated examples, elsewhere there was rather more (at Colin-Déleger and Leflaive and Sauzet) or very much less (at Leroy, Coche-Dury and the DRC).
Corks can vary, even within the same batch, if the wine-maker is not vigilant enough. Growers have been horrified to find that in some instances the sulphur level applied at bottling had practically disappeared a month later, while in a companion bottle it was all it should be. You can weigh corks to ascertain their density. The heavier the better. Philippe Prost of Bouchard is one who did this before Bouchard Père et Fils switched over to the DIAM closures in 2009. More and more people are changing to DIAM or GUALA, and to screw cap for their more basic wines, and a good thing too. It also avoids the problem of corkiness.
A second series of explanations concerned the wine-making. Generally speaking growers were using less sulphur, a protective and anti-oxidant. But they were employing batonnage, itself oxidizing. With the new, at the time, horizontal bladder presses the juice produced was squeaky clean, and perhaps more vulnerable. Some growers used to deliberately allow a little oxidation of the must right at the beginning. The theory was that it prevented oxidation later on. With global warming vines were being harvested early in Sepember when the weather was better - longer days and warmer ones too than three weeks later - and the gallop towards maturity was speedier. So did the wines have enough acidty? Was there too much of a touch of botrytis? Indeed why did just about everyone in Burgundy urge the malo-lactic fermentation? They don't in Bordeaux and Alsace and even in Champagne. Finally the soaking liquid used for making the corks more supple prior to bottling had changed from a sort of paraffin, seen as carcinogenic, to silicone or peroxide, again oxidative.
Moreover, there was a related further complication. The incidence of 'prem-ox' bottles was and continues to be distinctly higher in the USA than in France and Great Britain. How much did bad stoage come into the equation? It cannot be excessively high temperatures during shipment over the Atlantic, for all is shipped in refrigerated containers these days, nor in the customers private cellars, for surely these all have temperature control, if not at 12° (55 F) which is the ideal, then at 15°(60 F). No, I am talking here about the temperatures in the van and warehouse between port and private residence. There can be no other place where things can go wrong.
Some allege further mistakes in wine-making. Don Cornwell and John Gilman have addressed this in some depth.
There are two distinct oxidation process going on. One is the oxidation of flavonoid phenols. These come from the grape skins, seeds and stems, and more vigorous pressings will result in higher levels of these compared to whole cluster pressing and other less extractive techniques. The oxidization of these phenols results in the colour change in white wines from light, greenish yellow to golden brown.
The other, larger group of phenols are the non-flavonoid ones. They will be found in the pulpy part of the grape. They will oxidize over time but will not produce detectable changes in colour, flavour or aromas.
The second type of oxidation is the oxidation of ethanol. Ethanol is oxidized by the hydrogen peroxide present in the wine, producing acetaldehyde. The source of the hydrogen peroxide is from the oxidation of phenols. At a certain level of acetaldehyde the taster can perceive 'oxidized' aromas. The process can the protected by the use of sulphur dioxide as can the SO2 prevent oxidation of the flavonoid phenols. But sulphur's more important role is to react and effectively remove hydrogen peroxide. It is generally agreed that the flavonoid and non-flavonoid phenols play a greater part as the barrier to oxidation.
There are techniques such as hyper-oxidation which can and are being used, both in Burgundy and California. This is sometimes called 'browning of the must'. The idea is to remove 99 percent of the phenols from the wine. Fine, I would suggest for a Mâcon Blanc, but is is really going to result in a Corton-Charlemagne that tastes as we have come to expect at ten years old?
This is where the change in the sort of wine produced today comes in. They are lighter, they mature quicker, they contain less sulphur. They are therefore less protected. They will oxidize sooner. Wines are offered for tasting earlier, and so it is self-defeating to bottle them with the sort of sulphur content we used in the 1970s. They would not attract any sales. It would be idiotic to expect today's wine to be both delicious at a year and a half and to hold up for 15 years thereafter. Something has to give. I regret that it seems to be the ageing potential of the wine.
Since the worst of the vintages for 'prem-ox' (1996, 1997, 1998) there has been a welcome reduction in the incidence of bad bottles, but it still does occur. And yet there has been little scientifically published in France. More research, translated into a more rigorous understanding of what oxidation actually is, and how this specifically applies to premier and grand cru Burgundy, and this being taught in the wine schools of Beaune and the oenological degree couses at Dijon, is essential.