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Farewell corks?


November 1, 2012
By University of California ANR

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November 1, 2012 – While many cherish the mystique of popping a wine cork, screw caps are becoming more commonplace in the wine industry. Half a century ago, screw caps were associated with cheap rotgut wine, but now they have replaced corks in many premium wines and at many of the world’s best wineries.

Wine bottles are sealed primarily in three ways — natural corks, synthetic corks or screw caps. All have their advantages and disadvantages, and most certainly their proponents and opponents. While synthetic corks never gained much of a foothold in the wine industry, screw caps are being studied more frequently for their efficacy and quality.

While screw caps were originally thought to be airtight, resulting in the unpleasant aroma of hydrogen sulfide inside some sealed wine bottles, screw caps have been developed with different levels of permeability. Most aluminum Stelvin caps are lined with a polyvinylidene chloride–tin foil combination (Saran-Tin), or a polyvinylidene chloride–polyethylene mix (Saranex); each yielding different permeabilities, and chemical and taste profiles in the wine.

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Research is weighing the value of screw caps on wine quality and consumers’ ability to taste differences in wine bottled with a cork or a screw cap.

A new University of California – Davis study spearheaded by wine chemist Andrew Waterhouse, professor in the Department of Viticulture and Enology, is examining Sauvignon Blanc wine quality during aging, and consumers’ ability to taste differences such as oxidation in wine capped with natural cork, synthetic cork or screw caps. The UC Davis research team includes John Boone, a radiologist, and David Fyhrie, a biomedical engineer – both professors in the UC Davis School of Medicine – who will work with Waterhouse to analyze the corks, the wine colour and oxidation of the wine.

The study, which will be completed next year, is not touted to give a definitive answer to the best type of wine closure, but it will, according to Waterhouse, give winemakers reliable information on which to judge the type of closure that works best on their wines.

An earlier study at Oregon State University, and reported in Science News, said that consumers could not discern a difference in Pinot Noir and Chardonnay wines capped with natural corks or screw caps.

Perhaps what merits future study is the type of linings in screw caps. As screw caps continue to gain a foothold in the wine industry, it’s reasonable to assume that additional research on cap linings will produce additional options for winemakers, resulting in high-quality wines with greater longevity.

Based on research studies and wine experts’ judgments, here are some advantages and disadvantages of different types of wine closures:

Natural Corks

  • Traditionalists claim that “real” corks allow healthy gas exchange for flavorful wine
  • Some claim that good sources of natural cork are dwindling
  • Not all natural corks are alike, resulting in variable cork properties
  • Higher chance of “corked” wines and trichloranisole (TCA) taint

Synthetic Corks

  • Considered expensive and unpopular with consumers
  • Many synthetic corks let too much air into the wine bottle
  • They’re often difficult to remove from the bottle, and to re-cork the bottle

Screw Caps

  • Less chance that wines will be “corked,” and probably fewer tainted wines
  • Some say that air-tight screw caps are “suffocating” to wines