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What is premature oxidation? Ask Decanter

What is premature oxidation in wine, and is it still an issue today?

The vexed issue of premox – premature oxidation – in wine was a phenomenon that was first noticed in the early years of the new millennium, and seemed particularly (though not exclusively) to have affected white Burgundies produced in 1995/96 and on.

Wines that ought normally to have been capable of maturing over a long period, even from top-flight producers, were found to be showing signs of oxidising and tiring well before one might reasonably expect them to – colours dulling or fading to brown, fresh fruity aromas and tastes disappearing to be replaced by bruised apple, honeyed, waxy or stewed fruit characters.

The reasons behind the premox phenomenon were much debated and disputed at the time, and it’s still not really known for sure what combination of factors may have been the cause.

It seems to be generally agreed that prime causal factors in premox may have included shifts in thinking in viticulture and winemaking in the period starting in the mid-1990s, as producers were looking then to achieve greater ‘elegance’ and freshness in wines.

This was arguably driven by producers’ quest to achieve higher scores with younger wines in tastings and competitions, in an era when wine marketing and points-ratings were becoming increasingly critical to success, especially at the top levels.

Was premature oxidation a sign of the times?

It was also a time when producers (regulators and consumers, too) were becoming more conscious of the use of sulphur dioxide as an antioxidant in wine, and many were beginning to add less of it during winemaking, perhaps unaware of potential consequences in the longevity of the wines.

The mid-1990s was also a period when global demand for wine was growing and production expanding quickly around the New World in particular, but prior to the widespread adoption of the screwcap closure or the development of the advanced synthetic closures that we’re used to today.

It has been argued that there may have been a resultant general decline in quality or consistency in cork stoppers. For wines, this can result in excessive oxygen ingress in bottles stored over a long period – and that’s likely to include white Burgundies perhaps more than any other category of dry white wine.

Climate change and its effects on the ripening of grapes (no doubt less understood 25 years ago); moves towards organics and changes in chemical treatment regimes in vineyards; shipment and storage through the supply chain and in consumers’ homes or cellars; batch variation; bottle variation… all possible culprits, or contributory factors for premox.

And, of course, the longer a bottle is kept before opening, the more one has to accept a greater possible risk that the wine inside it might begin to deteriorate, in the normal manner of things.

Self-inflicted damage?

In Jane Anson’s 2014 feature, ‘Premox: has the crisis moved to red wine?’, she touched on the fact that, at the time, in the early 2000s, the implications of the premox phenomenon were so huge and potentially damaging that many in the wine trade found it hard to face up to.

Anson cites Professor Denis Dubourdieu (who sadly died in 2016) of the Institute of Oenology (ISVV) in Bordeaux – one of the team who led a groundbreaking study into premox in white wine in the early 2000s – who said: ‘We are used to identifying premature oxidation in the delicate aromas and colours of white wine, but when it [premox] was first discovered, nobody wanted to talk about it.’

Dubourdieu believed that there was ‘a similar scandal with red wine’. And, he said [in Anson’s November 2014 article]: ‘It’s not limited to one region; all red wines that are expected to be aged for long periods of time – so Barolo, Napa, Bordeaux, the Rhône, Burgundy and others – are in danger of ignoring this threat.’

Whether those fears were borne out or not is unclear, and may only now be evident to those still in possession of bottles from that period to open.

But Dubourdieu’s fellow researcher at the time, Dr Valérie Lavigne (now a global consultant specialising in the vinification and ageing of white wines, and still involved in research at Bordeaux university’s faculty of oenology) took a philosophical stance on the issue.

‘The problem is that many of us have become intolerant of acidity in wine,’ Lavigne said. ‘So winemakers do all they can to ensure soft, supple and fruity tastes. All of these potential issues [relating to premox] come from things that winemakers are [or were] doing with the best intentions. Ripe grapes, new oak, low sulphur use – these are all things intended to improve the wine and to benefit the consumer. But it’s important to warn that it’s possible to go too far.’

Is premature oxidation still an issue?

At the same time, there were those who doubted the supposed extent of the premox problem. Anson [in November 2014] quoted Dany Rolland, wife and laboratory partner of global wine consultant Michel Rolland, saying that it was really a matter of managing processes and correct winemaking: ‘We have seen premox in whites, certainly, but have not found issues with reds,’ she said. ‘We are used to working with very ripe fruit in Pomerol, St-Emilion, Argentina and California, but we simply protect the fruit and ensure stable conditions throughout the winemaking process.’

There have been other valuable and authoritative contributions to the premox debate published in various forums, from the likes of Jasper Morris MW, Clive Coates MW and Bob Campbell MW, offering varying opinions as to the causes and extent of the premox issue.

Looking back, more than two decades on, it’s probable that anyone buying white Burgundy for their cellar in that mid- to late-1990s period can count themselves as rather unfortunate. Caveat emptor…

However, the issue of premox in wine seems to have abated over time, and the debate in the trade subsided. It may well never be possible to know what lay behind it exactly – or whether it was simply a symptom of changing times and fashions.

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