The following post was originally in correspondance with a UK wine writer.
I am convinced cork has a future as long as its considerable past as a wine closure. That’s not from a “green” perspective but as a closure which contributes to the established expectations of knowledgeable and experienced consumers of traditional bottle ageing character and complexity, much as maturing in oak barriques contributes to complexity. There is limited science to support the active and positive role of cork in achieving mature wine bottle age character although the role of oxygen initially from within the cork cells and the possible catalytic role on condensation of wine phenols of cork derived compounds are recognised. There is in fact little science that has elucidated the oxygen mediated and ensuing auto-redox reactions and the products that form under cork across long bottle ageing time. It goes against my instincts and experience to say they are not important to ultimate bottle aged wine quality.
The flight to oxygen impermeable Stelvin was largely a response to the uncertainty of cork as a closure through the ‘80’s and ‘90’s. The TCA taint problem is part of the traditional ritual of accepting or rejecting a bottle at the table so is not just a modern phenomena but worsened in that period as demand on supplies became exponential with the global growth of table wine consumption. The suppliers seem to be solving that quality control failure restoring incidence levels to the long term averages which are an unavoidable feature of the variability of all natural products. (try the average for avocadoes). The cost of fine wine does make failure of the closure from taint an expensive failure but it is one that has traditionally been willingly shared by the consumer and producer depending on the age of the wine and the circumstance. Taint was not the major driver of Australian producers to Stelvin.
The systematic (not random) oxidation of white wine in bottle after a few years under cork during the ‘80’s and ‘90’s provided the main impetus to go to oxygen excluding Stelvin.
In truth that has not completely solved the problem of premature ageing because the cause is the oxidised phenols accumulated and retained in the wine under modern protective (anaerobic) winemaking regimes and amplified by the ideology has become to not fine or filter. Fining with casein, PVPP and other protein agents can reduce and prevent the phenols from polymerising and auto-oxidising. They don’t need further oxygen to initiate the chain of redox reactions which results in the formation of golden brown quinones and the associated detrimental organoleptic changes. Further in the vineyard, drier warmer seasons, more judicious use of irrigation, better canopy control and deliberate low cropping has led to earlier harvest in hotter, sunnier conditions and more exposed fruit.
This in turn causes greater phenol formation (carotenes) which are preserved through modern protective winemaking methods.
Hence even under Stelvin, producers are now fining to remove phenols and using ever increasing levels of free SO2 to achieve graceful ageing outcomes. Cork has wrongly worn the blame for this systematic oxidation phenomena which was as much a problem for white Burgundy as for Australian Chardonnay and Riesling in the ‘80’s and ‘90’s. Defective cork was probably at least partly responsible for the occasional bottle (up to 1 in 2) of oxidised white wine which was the condition described as “random oxidation”. Even there the wine was predisposed to being tipped over the oxidation edge by viticultural and winemaking practice.
Recognising the reduction problems of the complete seal of Stelvin and the possibility of the positive role of some oxygen in bottle ageing, new oxygen permeable liners have become available for Stelvin. The problem is that they introduce oxygen on a continuous straight line basis throughout the ageing life of the wine which is certainly not emulating the non linear involvement of oxygen under cork.
To speak out in favour of cork and the possibility of its positive contribution to wine quality is to invite pariah status in Australia much as climate change sceptics are scorned in public debate and accused of being “deniers”. The influencers have been so influenced and have so harangued the market into submission that it has now almost become a commercial imperative to bottle under Stelvin.
Back to my position. Having first used Stelvin in 1977 and 1978, I have long been aware of the risk reduction provided by the closure and its appropriate place in the commercial market for wines consumed quickly. I am equally convinced that the best wines age best under good cork if the wines have been grown and made appropriately (true for the cork as well).
So Tapanappa has bottled exclusively under very expensive and good cork up until 2010. With the introduction of out “Wines of Terroir” regional wines for the Piccadilly Valley (Chardonnay), the Fleurieu Peninsula (Pinot), and Wrattonbully (Cabernet/Shiraz), these less expensive and probably earlier consumed wines (than our Single Vineyard wines) have been put under Stelvin. I have also bottled some Single Vineyard Tiers Chardonnay and Foggy Hill Pinot under Stelvin in 2010 but am not sure I will repeat that when we have another single vineyard vintage. The use of Stelvin for the “Wines of Terroir” is mostly commercially driven, responding to what the Australian wine press, the retailers and indoctrinated consumers are demanding.
Stelvin is much cheaper than good cork so its use is cost effective, risk reducing and market appealing. So why would anyone in their right mind use cork? Because of the possibility that the wine might be greater after ageing under cork than under aluminium and plastic.