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Cork closure for wine bottles is timeless. The sound of popping, the tradition, and the romance around uncorking a bottle are without a doubt alluring. For centuries, cork stoppers dominated the market as the standard solution for sealing wine bottles. But innovation and technological advancement in wine packaging has challenged that monopoly, providing a wealth of alternative sealing devices to winemakers worldwide.

Wine Closures: Cork, Screw Cap, Glass Stopper & More

The fundamental purpose of any wine bottle closure is to preserve the wine - to prevent an excessive amount of oxygen from getting in - during storage and transportation. For a wine producer, a single bad bottle can be detrimental to the brand’s reputation.

Hence, innovative companies, backed by extensive research and product trials, are experimenting with materials and closure technology year after year to offer better, practical sealant solutions. As a result, the wine closure options continue to expand.

Here are some of the contemporary alternative wine closures commonly used by wine producers today:

  • Screw Cap (Stelvin Cap)

Screw caps were first patented and commercially produced in the 1970s in Australia under the brand name Stelvin. With approximately one-third of the wines produced globally flaunting the aluminium screw cap seal, it is by far the most popular non-cork wine closure on the market. But making this significant headway in an industry dominated by cork has not been easy. Screw caps were adopted by the industry out of frustration: a lesser understood chemical compound called TCA (2,4,6-trichloroanisole) contaminated the cork, giving a musty smell and flavors of moldy cardboard to the wine. Although not harmful, it made the wine very unpleasant to drink. In the 1980s, as the quality of corks started deteriorating and winemakers ran into more corked bottles (as high as 10% by some records), the search for alternative solutions gained momentum. However, the first real shift to screw caps took place in the 2000s when a group of Clare Valley Riesling wine producers banded together in favor of this wine closure. Soon, New Zealand joined the screw cap revolution.

For over 40 years, screw or Stelvin caps have proven to be effective in maintaining the freshness and bright fruit flavors of wine, particularly those meant for early consumption. Plus, they are watertight, airtight, free from TCA, and can be twisted open by hand without requiring any special device. While in countries like Australia and New Zealand, wines of all styles and price points are sold with a screw cap, traditional wine regions like France and Italy are gradually making the move.

  • Glass-on-glass Stopper (Vino-seal/ Vino-lok)

In the 2000s, Alcoa, a German company, came up with these elegant glass-on-glass closures, which resembled decanter tops. As glass is inert, it eliminates the possibility of cork taint, and the plastic O-ring attached to it creates a tight seal. Also, it easily fits back into the bottle. Marketed under the names Vino-Lok and Vino-Seal, these wine bottle closures are preferred by dozens of reputed wineries for their classy look and environment-friendly, reusable, and resealable features.

  • Zork

Developed in Australia, Zork is an award-winning synthetic wine closure that combines the convenience of a screw cap with the pop of a cork. It simply requires the user to peel off the bottom part of the outer cap and then lift the top part. Available in still and sparkling wine versions, Zork closures are resealable, reusable (on similar bottles), recyclable, and eliminate the need for a corkscrew or any other wine gadget.

  • Crown Cap

Though crown caps are more associated with beer bottles or similar fizzy beverages, it is a choice of seal for traditional method sparkling wines/Champagnes undergoing secondary fermentation in the bottle. Upon disgorgement (the technique of removing frozen dead yeast or sediment remaining in the bottle after the second fermentation), the cap is replaced with a cork and released into the market.

The exception to this worldwide practice is natural sparkling wines like Pétillant Naturel (aka Pét-Nat) and the Col Fondo Prosecco (Sui Lieviti), where bottles are frequently sold with crown cap closures. These sparklers are not disgorged, resulting in a lightly sparkling wine with a bit cloudy appearance.

Given the crown cap's ability to contain pressure, economic viability, ease of opening (in contrast to cork closures), recyclability, and youthful appeal, many prominent sparkling wine producers, from Loire Valley to California, are making a move toward sealing their younger-style sparklers with crown cap closure.

Closure technology is evolving for cork stoppers as well

Natural cork has been the gold standard for wine closure in the world for over 400 years, with Portugal and Spain leading cork production. It is leak-proof and permeable, meaning, corks allow a tiny amount of oxygen into the wine. This is important because it helps the wine to age and evolve in the bottle over time.

But being a natural product has its own merits and challenges. As natural cork is made from the bark of cork oak tree (Quercus suber), it is biodegradable. It is also ideal for sealing the wine as it adapts to all irregularities of the bottleneck, even if the glass expands or contracts with the temperature differences. On the other hand, natural corks have variable quality and rate of breathability; it is a limited resource, hence expensive. Its biggest drawback, however, is the contamination caused by TCA (cork taint), which spoils the flavors and aromas of the wine.

In the early 21st Century, anywhere between one to ten percent of the wines suffered from cork taint, due to which natural cork fell out of favor. Cork’s declining sales along with the dramatic rise of alternative wine closures stirred up the cork suppliers.

With a focused effort to reduce cork contamination, even secure a TCA-free future, and win back the confidence of the wine industry, in came the new cork variants.

  • Agglomerated Cork

Think of these as the cork equivalent of particleboard. They are a low-cost option made of natural cork bark scraps, cork dust, and glue. Agglomerated corks look like natural corks; they are pretty dense and homogeneous compared to natural corks. Though they work as an effective seal, agglomerated corks are best suited for young wines meant for consumption within a year.

  • Technical Cork

Originally developed in Portugal in the 1980s, this type of cork closure consists of a very dense agglomerated cork body with natural cork discs glued on either end (and sometimes on both ends). It is chemically very stable and mechanically very strong. Technical corks use humidity treatment to remove contaminants (TCA) from the granules, while the end disk(s) are imaged, X-rayed, and individually inspected. Usually, Technical corks are used for wines that are destined to be consumed within two to three years.

  • Synthetic Cork

These wine closures are made from either petroleum-based plastics or plant-based plastics and provide fixed, predictable oxygen transfer rates and a tight, immovable seal. Synthetic corks are cheap, sometimes even lower than screw caps; they do not dry out (so you can store wine bottles upright) or crumble (no fishing pieces out of the wine). But on the flip side, Synthetic corks are often difficult to remove and reseal (particularly the petroleum-based variant), and can leave a chemical odor in the wine if stored for long periods. Hence, it is practical to avoid these closures for age-worthy wines.

Much like the emotionally charged discussions on sports and politics, the debate on whether cork is better than alternative closures (specifically screw caps) has been rife in the wine industry for a very long time. And developments in the wine closure industry over the past two decades have shifted that discussion to a new height.

Today, producers and winemakers can choose a closure based on the style of the wine, grape variety, target price of the final product, consumer's acceptability in the market it is intended for, convenience, and sustainability. It is safe to say that all closure variants will have their place in the ever-growing wine industry, the same way e-books coexist with paperbacks.

Whether you are a cork traditionalist, screw cap devotee, or an early adopter of alternative stoppers, don’t judge the wine inside the bottle by the closure alone.
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