Friday, May 23, 2008

New High-tech Wine Cap Design: An advance, Or...

A competition, called Big Bang, founded in 2000 by students at the UC Davis Graduate School of Management has awarded its top prize of $15,000 to a design for a new wine bottle closure that would allow the wine to breathe much like traditional bark corks.

The folks behind this certainly seem to have all the knowledge and experience needed to do this.

Their team, Advanced Enological Closures, set out to design a better bottle cap because cork taint, a byproduct of a fungus that infects cork and makes wine smell like moldy mop water or sweaty gym socks, now contaminates the corks of an estimated one in 20 wine bottles on store shelves, ruining billions of dollars of wine annually. Although synthetic corks have been developed in response to the problem, they allow too much oxygen into the bottle, according to Keller. Overly oxidized wine has a shorter shelf life and can develop a fingernail-polish odor. Screw caps -- another alternative to bark corks -- are a viable option for wine white, but do not allow in enough oxygen for fine red wines, Keller said. Without enough oxygen to draw on, red wines start to smell like burned rubber or matchsticks as they age. LINK

But wait! The idea does seem a bit strange, especially given that oxygen is the enemy of wine.

The team's design, a "breathing screw cap," has small vent holes and is fitted with a liner made of alternating layers of thin metal and a porous polymer. The liner can be customized to allow optimal oxidation for specific varietals, something that is impossible with bark corks. A patent is pending for the design.

"If you open up lots of bottles of the same wine, you'll notice variability from bottle to bottle because of differences in the amount of oxygen that gets in," Keller said. "With cork, you just never know. Our product will give a level of control that the wine industry has never had."

Then there was this.

Keller's design offers the prospect of a cap that eliminates the worry about taint while still letting in oxygen.

His team's patent-pending design – which so far lacks a catchy name – is a 5-cent disc that fits beneath a screw cap. Made from alternating layers of polyethylene – the same material used to make sandwich bags – and perforated aluminum or tin, it can be fine-tuned to match the oxygen demands of different varietals.

"Pinot noir needs a little, cabernet sauvignon needs a lot," Keller said.

That last statement sounds just a little, no make that a lot, like rubbish. It is known that oxygen levels can vary among different grape varieties, but that has been demonstrated during the winemaking process. To my knowledge there is no evidence that different grape varieties require different levels of infusible oxygen during aging. To reconfirm just how important a lack of oxygen is to wine I turned to the best source of knowledge on screwcaps, Tyson Stelzer. Here is a little of what he wrote in 2007.

The question of the ageing rate of wines in screw cap has been a hot topic of late. It is my belief that the rate at which mature notes (or "characters," as we say Down Under) develop in screw-capped wines is in fact absolutely no different to that under traditional closures. This is evidenced by the fact that wines under screw cap age at a similar rate to those with the very best corks. For a wine under an average cork, however, oxidation effects give the impression of accelerated ageing, which has led to the notion that wines mature slower under screw caps. I believe that the absence of oxidized characters in screw-capped wines gives the mistaken impression of slower ageing.


More criticism has been levelled at screw caps by the media in relation to reductive characters than any other fault. I encourage you to view these accusations objectively and judge for yourself. If there is a causal link between screw caps and reductive characters, as some claim, then we should be tasting more reductive wines under screw cap than under cork.

Check it out for yourself, but my experience, and that of hundreds of experts with whom I have had this conversation, is quite the opposite. In my own tastings in recent years, comprising thousands of predominantly Australian and New Zealand wines, I have encountered more reductive wines under cork than I have under screw cap.

The managing director of the AWRI, Professor Sakkie Pretorius, commented recently that "The idea that there is a high incidence of post-bottling reduction in wines sealed with screw caps is a false premise. With Australian wines, where the AWRI has particular expertise, this is demonstrably not the case…. Our position, which we believe is undeniable, remains that the propensity of a wine to develop 'reductive' aromas post-bottling is a function of the wine, and that post-bottling reduction is not the 'fault' of the closure but may be exacerbated by the closure if the wine has a propensity for such aromas to develop."

"In his Screw Cap Symposium presentation, Peter Godden discussed data from one of our AWRI Advanced Wine Assessment Courses which indicates a higher incidence of reduction in wines sealed with cork compared to wines sealed with screw caps. Two subsequent courses have provided similar data."

That seems pretty clear to me.

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