Oxygen Not Necessary for Ageing Bottled Wine
In a Press Release Allen Hart, Southcorp's Research & Development Winemaker, described a study that has concluded that closures which allow very little oxygen to enter bottled wine do not affect the maturation of the wine. Hart concluded: "From this study it is apparent that oxygen was not a vital component for the ongoing evolution and maturation of these red wines after bottling. It is clear that access to small but measurable amounts of oxygen (eg synthetic closures), will accelerate the evolution and maturation of red wine through oxidative reactions. However, red wine will continue to evolve without measurable oxygen ingress via a closure, primarily through what is assumed to be anaerobic reactions. Some bottled wine may express "reductive" characters in such an anaerobic environment, in contrast to the wine developing oxidised characters in a more aerobic environment (but the rankings indicated that these) are not considered commercially unacceptable."
These observations are very similar to the studies of the Australian Wine Research Institute (AWRI) reported by Tyson Stelzer. Stelzer expanded on the Southcorp Press release in a post to the Mark Squires Bulletin Board of eRobertParker.com. See here. Several points bear noting. One of the wines used was the 1996 vintage of Penfolds Bin 389, a wine that can age for at least a decade and often longer. Various analyses (chemical, spectral, sensory) were done at 2.5, 4.5 and 6.5 years post-bottling. The data collected suggest that in wine bottled with ROTE (roll-on tamper-evident) or screw-cap closures, “the phenolic reactions that influence wine colour are still progressing even in the practical absence of ongoing oxygen for reaction. This allows the wines colour and tannin structure to continue to evolve with time."
So is wine development really a reductive process after all? You would think that we would know this by now. But we’ve never had a really efficient closure system to limit oxygen access before, unless you want to put your cellar under vacuum!