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Cork purity battles pit ‘natural’ wine stoppers against elastomer-based versions

Four California winemakers have recorded a video explaining why they've joined the 100% Cork initiative and only use natural cork to seal their wines. The reasons the winemakers stated for their natural-cork preference ranged from the view that natural cork allows buyers to age wines to the belief that it imparts flavors to wine, including creaminess, nuttiness, and "spicy vanilla".

and only use natural cork to seal their wines. The reasons the winemakers stated for their natural-cork preference ranged from the view that natural cork allows buyers to age wines to the belief that it imparts flavors to wine, including creaminess, nuttiness, and "spicy vanilla". The initiative is sponsored by the Portuguese Cork Association and the Cork Quality Council.

Lance Ignon of 100% Cork told PlasticsToday that cork holds a 65% share of the global market for wine closures, and in the U.S. it is once again gaining share after ceding ground to alternative stoppers over the past decade. Ignon said plastic-based stoppers seemed to have the most negative momentum. "Among alternative stoppers, the ones made from plastic are losing the most ground," Ignon said. "Notwithstanding the innumerable good uses for plastic, they haven't caught on well as wine closures." Ignon added that in his view the elastomer-based corks tend to leak, causing oxidation of the wine, and in general they have met "significant consumer resistance."

Harvested from the bark of cork trees grown in Portugal, as well as Spain, natural cork is promoted as renewable and biodegradable. In an article comparing the wine-stopper options, natural cork, synthetic cork, and screw caps, online wine retailer CellaRaiders Inc. noted that despite environmental benefits, natural cork does pose some issues, including breakage, difficulty removing, and leakage that can allow oxygen to reach the wine and spoil it. The site estimated that 5% (others put that number as high as 12%) of wine bottles are affected by faulty corks, which is part of the reason vintners have turned to screwcaps and synthetic corks. Ignon and 100% Cork dispute the 5% figure, noting that the most recent issue of Practical Vineyard and Winery Journal put the rate at 2%, with some studies pegging the figure closer to 1%.

The article said that while synthetic cork, which is typically made from thermoplastic elastomer (TPE), is cheaper to make, can be produced in virtually any color, and it won't dry out, some wine enthusiasts are concerned that a complete embrace of the product could lead to the end of cork forests. It also stated that while synthetics block oxygen 100%, preventing any chance of spoilage, there is some belief among winemakers that a little oxygen aids wine maturation. Estimates vary, but some market watchers put the number of bottles topped with TPEs at 7-9%.

The final option, screw caps, bear the stigmatism of being used for cheap wines, but CellaRaiders points out that many winemakers in the U.S. and New Zealand, for example, have opted for them. In spite of claims that screw caps provide a better seal for wine than corks, the article points out that most screwcap manufacturers will only guarantee the closure for 2-3 years.

A 2009 survey of 229 U.S.-based winemakers by Wine Business found some significant shifts within cork material usage from 2004 to 2009. The percentage of wineries using so-called technical corks in that time period rose from 20% in 2004 to 30% in 2009. Technical corks are composed of a granulated natural cork body with a disk of high-quality natural cork at each end. Synthetic corks over that same period, however, saw their usage slip from 30% in 2004 to 20% in 2009. The biggest winner was screw caps, jumping from being used by only 5% of wineries to 26%. 

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