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Experts Joust Over Wine Closures

Merits and sustainability of corks, synthetics and screw tops debated at Davis forum

by Andrew Adams
wine closures panel
Maurizio Ugliano, research manager for synthetic cork maker Nomacorc, describes sustainable steps taken by the company at a panel discussion about wine closures. Dr. Andrew Waterhouse, seated far left, moderated the panel, which also included VinPerfect founder and CEO Tim Keller (center) and Peter Weber the executive director of the Cork Quality Council.

Davis, Calif.—While consumers find plenty of room for argument about which wine is No. 1, winemakers and suppliers can be just as combative about which closure is best.

As part of its ongoing Wine Flavor 101 series of lectures and seminars, the University of California, Davis, gathered representatives from the cork, synthetic and screwtop camps for a forum held Thursday on campus.

Late in the afternoon during a panel discussion about the sustainability of closures, Tim Keller, founder and CEO of VinPerfect, the new company that has patented an oxygen-permeable liner for aluminum screwtops, made an aggressive pitch for the sustainability of aluminum closures vs. the cork industry’s sustainable claims.

Keller said much of the cork industry’s claims to sustainability are built around an image of a beautiful cork tree in Portugal and are what U.S. Vice President Joe Biden would refer to as “malarkey.” He added, “we would be remiss if we didn’t confront it directly.”

Prior to the discussion, UC Davis’ Dr. Andrew Waterhouse—who moderated the panel—requested panelists not focus on claims made in privately funded closure research.



    The Wine Flavor 101 series of lectures continues Jan. 11 with a discussion of Brettanomyces. University of California, Davis, experts and winemakers will explore the potentially beneficial aspects of Brett. A winemakers’ panel also will discuss and taste through wines exhibiting Brett as part of their terroir. Dr. Linda Bisson will unveil her new Brettanomyces Aroma Impact Wheel. The session is from 9 a.m. to 4 p.m. and costs $200 with lunch and wine tastings included.  For more information visit:

Sustainability claims questioned
Keller, however, went right at Corticeira Amorim’s “life cycle” analysis report (released in 2008), which concluded that cork had a far lower output of carbon dioxide than competing closures. He said the report is largely based on the premise that cork forests provide a natural offset to the emission of greenhouse gases through cork production and shipment. Yet Keller argued the cork forest would keep growing and absorbing CO2 even if the wine industry stopped using cork, so it’s inaccurate to use the natural forest as an offset to production. “The cork forest is a non sequitur,” he said.

He went on to say that aluminum is almost exclusively manufactured using hydroelectric power and is an excellent material for recycling. “You don’t see people wandering around the streets with bags of corks,” he said. “Aluminum will be recycled because it’s profitable to do so.”

Keller also argued that natural cork’s rate of failure also outweighs any sustainable claims when one considers a consumer pouring out a tainted bottle of wine represents a complete waste of production and transportation resources.

Following Keller’s remarks Waterhouse said he felt compelled to make a response because he had specifically asked the panel not to refer to the life cycle report in question. He criticized Keller for attempting to undermine the sustainable value of the cork forest with “scanty data” while he had not even completed and released a life cycle analysis of VinPerfect’s production chain.

Keller conceded he lacked his own life-cycle analysis but made his second political reference by saying President Obama appeared to lose the first presidential debate because he didn’t aggressively confront the claims of his opponent. He said he’s not “anti-cork,” he just wanted to refute some of the claims made by the industry.

Peter Weber, executive director of the Cork Quality Council, wryly noted after Keller’s remarks that he was glad someone was able to use the images and content of the report he had been asked not to present. He went on to say that cork is naturally sustainable and has been endorsed by the International Organization of Vine and Wine, the World Wildlife Fund and other groups.

Weber said some of the trees being harvested for cork are 250 years old, and the United Nations has concluded the forests are environmentally and economically sustainable. He said the trees provide a definite offset to carbon dioxide production. “It’s small, but it can be an offset and that’s important.”

On the synthetic side, Maurizio Ugliano, head of research for Nomacorc, said the company has reduced its per-closure CO2 rate of 16 grams in 2007 to 11 grams per closure this year. He said that’s far less than the lowest per-bottle production output number for bottles he’s seen of 1.28 kg of C02.

Before leaving the panel early to catch a flight to Italy, Ugliano also noted that if just 3.5% of corks are tainted and only 35% of consumers detect the taint and pour the wine down the drain, that waste has a far larger impact than any CO2 generated through production.

Following the panelists’ remarks, Waterhouse sought out the input of Glenn O’Dell, the director of quality improvement for Constellation Brands Inc., which had earlier in the day discussed conducting closure trials.

O’Dell said the carbon footprint of the closure industry is relatively minor and there really is not enough research to conclusively state which closure is the better option in terms of being the most sustainable. “I don’t think anyone has enough information at this point to say who can wear the greenest hat,” he said.

Which is the best?
If there is uncertainty about who is the greenest there’s still plenty of room for debate about which closure is the best. After presentations by Weber, Keller and Ugliano about the merits of each of their respective closure types, one was left with the answer to so many of winemaking’s questions: it depends.

Weber attested to the cork industry cleaning up its taint and quality control issues and reported the latest consumer survey found more than 90% of those polled thought wines with corks to have “high to very high” quality. Keller detailed the steps VinPerfect has taken to dial in its liner to deliver a precise level of oxygen that avoids reductive or oxidized characteristics. Ugliano described how Nomacorc provides a line of closures with different oxygen transfer rates so winemakers can specifically target desirable traits in their wine. He noted as an example that his research found the closure with a higher oxygen rate could provide more chocolate notes over 18 months of aging. “We could modulate these chocolate aromas to our convenience,” he said.

O’Dell said he has been studying the different types of closures for 25 years and has yet to find a definitive answer for which is the best. “Most people want a simple answer. I’m still looking for one,” he said.

He said wineries have to run closure trials through their bottling lines as it’s impossible to really determine how a closure will work with your production process unless you’re working with “live bullets.”

He said the latest luminescent equipment to pinpoint total oxygen levels have been invaluable in improving the effectiveness of his closure trials. When asked about running different closure types through a line without stopping it for consistency, O’Dell said he’s thrown different closures into the hopper and just run bottles with light sensors through the line and has been able to achieve enough representation for each type for the trial.

Screwtops require the line to be shut down, so O’Dell said he’d probably switch to using a mobile line for screwtops so the same wine could be bottled with different closures concurrently.

Each closure has its own strengths and weaknesses, so the question is more what closure fits your wine than which is the best. O’Dell did say the oldest option is still one of the most effective. “If the cork industry could deliver anything close to 100% good corks efficiently we would not be having this discussion today.”


Posted on 05.07.2013 - 15:50:36 PST
Diam closures offer all the advantages of natural cork w/none of the TCA and permeability problems of traditional natural corks. I've used them now for 10 years, with no corked bottle returns, and great consistency in aging. Admittedly on a small, 1000 cs/yr, scale.
David Noyes

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