Closure
Closure in wine refers to the device used to seal a bottle, protecting the contents from spoilage, oxidation, and loss of carbon dioxide in sparkling wines. Beyond a purely practical role, closures influence how a wine matures, and they remain one of the most debated aspects of modern winemaking.[1]
Definition and function
Closures serve to maintain the integrity of wine from bottling to opening. They regulate the ingress of oxygen, prevent contamination, and affect the rate at which a wine develops in bottle.[2] The choice of closure can therefore have significant implications for style, shelf life, and consumer perception.
Historical development
The use of natural cork as a closure became widespread in the 17th century, coinciding with the adoption of glass bottles as a standard container.[3] For centuries, cork remained almost unchallenged as the dominant method of sealing wine. In the late 20th century, however, concerns over cork taint (caused by trichloroanisole, TCA) and inconsistency in performance led to the exploration of alternatives, including screwcaps and synthetic stoppers.[4]
Types of closures
Natural cork
Natural cork closures, made from the bark of the cork oak, remain the most traditional choice. They are valued for their elasticity and micro-permeability, which allows small amounts of oxygen to enter the bottle and contribute to controlled ageing. Their principal drawback is the risk of cork taint, as well as variability in performance.[5]
Technical cork and synthetic closures
Technical corks, made from agglomerated particles of cork, and synthetic closures emerged as alternatives designed to reduce cost and minimise the risk of taint. Synthetic closures, often made from plastic polymers, provide consistency but have been criticised for allowing excessive oxygen ingress over long storage periods.[6]
Screwcap
The screwcap was introduced into the wine sector in the late 20th century and rapidly gained traction, particularly in Australia and New Zealand. Research from the Australian Wine Research Institute demonstrated that screwcaps provided excellent protection against oxidation and variation, with wines maintaining freshness longer compared to cork-sealed equivalents.[7] Despite this, screwcaps have faced resistance in some markets due to traditional associations with cork.
Other closures
Glass stoppers, have found limited adoption, particularly for premium white wines. Crown caps, commonly associated with beer, are occasionally used for sparkling wine during bottle ageing and, more rarely, for still wines as a final closure.[8]
Impact on wine quality
The main technical consideration in closure performance is oxygen transmission. Small, consistent oxygen ingress can aid in the softening of tannin and development of aroma complexity, whereas excessive oxygenation leads to spoilage. Studies have shown that different closures vary widely in oxygen transmission rates, affecting ageing potential.[9] Research comparing screwcaps and cork closures highlighted that screwcaps generally offered the most reliable barrier, though some winemakers argue that cork’s variability can lend character to long-aged wines.[10]
Contemporary debates
The closure debate encompasses both technical and cultural dimensions. While many New World producers favour screwcaps for their reliability, Old World regions often continue to prefer cork due to tradition and consumer expectation.[11] Current research focuses on refining closure technology to balance oxygen control with consistency, ensuring wine quality across diverse markets.
See also
References
- ↑ Robinson (ed.), The Oxford Companion to Wine, Oxford University Press, 2015.
- ↑ Jackson, Wine Science: Principles and Applications, 5th ed., Academic Press, 2020.
- ↑ Robinson (ed.), The Oxford Companion to Wine, 2015.
- ↑ Jackson, Wine Science, 2020.
- ↑ Robinson (ed.), The Oxford Companion to Wine, 2015.
- ↑ Jackson, Wine Science, 2020.
- ↑ Godden et al., “Closure performance: Australian Wine Research Institute study on screwcaps and cork”, Australian & New Zealand Wine Industry Journal, 2001.
- ↑ AWRI, “Closures and wine quality”, https://www.awri.com.au
- ↑ Jackson, Wine Science, 2020.
- ↑ Godden et al., 2001.
- ↑ Robinson (ed.), The Oxford Companion to Wine, 2015.