Wine and cork have gone hand in hand for a very long time. As early as 500BC cork was used as a wine jug stopper in ancient Greece. Since the 18th century, cork has been the preferred choice following Dom Perignon’s success in bottling champagne. Cork helps create an airtight seal, preventing oxidation and early aging. But the last 50 years have seen a growing push for alternative bottle toppers in order to combat dreaded “cork taint”, caused by the presence of the chemical Trichloroanisole (or TCA). Currently, major bottle closure options include natural cork, technical cork, synthetic plastic cork, screw caps, Zork, and Vino-Seal. However, the best wine bottle closure doesn’t even exist yet. Current science, research, and technology efforts are improving our understanding on the interactions between wine, bottle, and cork, and the future holds an exciting time – a time in which bottle closures will be specifically designed to shape the flavor of wine and define a precise aging timeline.
What Percentage of Wine Bottles are Affected By Cork Taint?
If you read five different studies, you’ll hear five different things. Looking at the results from many different sources, it seems the best guess is somewhere around 1-3%. Some studies have found TCA affecting less than 1% of wines, while others have claimed that 8% of all wines are affected. A 2008 and 2009 survey of judges at the Indy Wine Competition by Christian Butzke, enology professor at Purdue University, showed that fewer than 1% of wines were affected. However, James Laube of Wine Spectator has reported findings over 7% (article is restricted access to only members online, so I won’t link to it).
In actuality, even if cork taint does affect a sizable percentage of bottles, research suggests many consumers won’t know about it. A great paper by Berenice Barker of the Cape Wine Academy details several studies that suggest that even trained professionals have a very hard time detecting the minute quantities of TCA that often exist in faulty wines. In the eyes of consumers, it may appear that the actual rate of cork taint is essentially 0%.
The State of Cork Alternatives
The screwcap was first released in 1973 by French company Le Bouchon Mecanique, designed to eliminate cork taint and protect the freshness in wine. Several Australian wineries were influential in the development and perfection of the closure including Yalumba, Penfolds, McWilliams, Hardys, Seppelt, Brown Bros and Tahbilk. The screw caps were used sparingly until catching on in 2000, when a group of Clare Valley (Australia) winemakers banded together to place a large order for 250,000 closures from French manufacturer Pechiney. Soon after, New Zealand wine makers formed the New Zealand Screwcap Wine Seal Initiative, starting with over 30 winery members and encouraging the usage of screw caps. Currently, more than 85% of New Zealand wines and over 45% of Australian wines are bottled with screw caps. In the US, approximately 25% of wineries use screw caps. The 2009 Closure Report by Wine Business Monthly summarizes the data in its annual survey of US wineries:
Chart from Wine Business Monthly
What is So Special About Cork?
The secret to the success of cork may not be the impenetrable airtight seal, but actually the precise amount of oxygen it actually lets into the bottle. Recent research by the University of Bordeaux has determined that the oxygen transmission rates (aka permeability or OTR) of cork lies somewhere between the higher OTR of synthetic plastic cork and lower OTR of Stelvin screw caps. It has often been said that it is this property of cork which leads to successful aging in wine, and that bottles with synthetic corks will age and spoil too quickly while bottles with screw caps will age slowly or not at all.
Does The Oxygen Permeability of Cork Help The Wine Aging Process? Can Other Closures Do This Too?
Numerous studies suggest that oxygen transfer through the cork plays only a partial role in the aging of wine. Perhaps more important is the bottling process – the dissolved oxygen present during bottling, the oxygen “headspace” within the bottle, and the concentration of the antioxidant sulfur dioxide (SO2). The ongoing research by the Australian Wine Research Institute (AWRI) asked “does wine require oxygen to age or develop? The answer is probably no…” The AWRI research found that screw caps, with the lowest oxygen trasmission rates among closures, actually were the best at preserving wine. They also found that the OTR of corks varies widely, and the best corks actually have less oxygen ingress than most screw caps.
There is no doubt that if oxygen permeation does occur in a bottle of wine, it will affect how the wine ages. The question is, what level of oxygen permeation is best? The important thing to remember is that screw caps and other closures can be engineered to allow specific oxgyen ingress rates. If it is proven that certain oxygen rates work best for specific wines, then screw caps or other closures can be manufactured to provide this permeability.
Does The Choice of Bottle Closure Influence The Flavor of Wine?
In the most extreme cases, cork can impart flavors of wood, mustiness, earthiness and cork taint. On the other end of the spectrum, it is said that certain screw caps, with their reduced oxygen permeability, can cause “reduction” and impart aromas of “rotten-egg” caused by hydrogen sulfide. Several studies have analyzed the reduction process and this report within Wine Business Monthly does a good job presenting them.
However, when bottle closures behave as intended, the perfect oxygen ingress rate can help preserve fruit freshness and balance, and help a wine age in full complexity and brilliance. There are examples that suggest that screw caps can age wine just as well as natural corks. But the ultimate flavor of a wine is a culmination of the entire process: the grapes, fermentation, chemical treatments, oak and steel aging, bottling and bottle closure. Each combination will achieve a unique creation.
Nomacorc sensory description of wines
The Future of Wine Bottle Closures
Its an exciting time as current science, research, and technology efforts are improving our understanding on the interactions between wine, bottle, and cork. In late 2007, synthetic closure manufacturer Nomacorc announced a multi-year project with UC Davis and several other leading wine institutions to understand how oxygen ingress can affect taste, aroma, structure, and color. Results from studies like this will help bring more refined closure options, each designed for a specific purpose. Once winemakers can fully understand how oxygen affects wine, they may, for example, look to use a closure with a low OTR to help bring out vegetal characteristics, or a high OTR to quickly produce intense fruit notes. Wine labels may increasingly include aging timelines with precise maturity dates. Even better, winemakers may eventually be able to quickly simulate the effects of long term aging within months or several years. Each day we’re all one-step closer to a $10 wine that tastes the same as a 15 year old cellar-aged masterpiece. I’m ready for it.
