With an average lifespan of years, each tree can provide thousands of bottle stoppers when cared for properly. The short version of the cork life cycle goes like this: Happy cork trees grow to age 25 in semi-arid forests surrounded by other animal and plant life on the Iberian peninsula and North Africa. After that, skilled cork harvesters use axes to slice off the outer bark of the tree, leaving its inner wood intact and undamaged. Then, the planks of cork bark are dried, sorted, and processed.
To make the bottle stoppers we know so well, slices of cork are boiled to remove impurities like the chemicals that cause cork taint and dried until they reach the optimum texture to be pressed into bottles. Over nine years, the outer bark slowly regenerates before the next harvesting cycle begins.
Cork oaks are the only oak whose bark regenerates in this fashion, making Quercus suber a very special tree. On a cellular level, cork looks like a honeycomb of air pockets. Before cork taint frightened so many winemakers into abandoning cork, the material had helped to successfully preserve fine wines for centuries. This feature allows a cork to be pressed into a smaller physical space and yet spring back to its original form when removed. Step after step, cork absorbs the pressure and then instantly springs back to its original form, no worse for the wear.
Following the cork-taint scare, the cork industry set out to improve both its product and its image. Cork producers invested in new equipment and worked to refine production techniques, contributing to a sharp decline in tainted wine. Once stripped from the tree, the cork bark grows back and is harvested again a decade later. Stripping a cork oak of its bark also enhances its ability to absorb carbon dioxide ; in Portugal alone, cork trees help offset over 10 million tons of CO 2 every year.
According to the World Wildlife Fund, these forests contain the highest levels of plant diversity found anywhere in the world —reaching levels of species per square meter—while also providing a habitat for endangered animal species like the Iberian lynx and Barbary deer. Demand for cork products, especially wine stoppers, helps preserve the cork forests, which would otherwise be neglected or replaced with non-native trees.
The damage control appears to be working, at least in part. Recently, I asked the manager of my favorite bottle shop if anyone bought cork anymore. Wines cellared for long periods of time must be kept on their sides to keep the cork damp. But even with careful cellaring, how many of us have fished the remains of a crumbled cork out of our wine after it breaks on its way out of the bottle?
Depending on the quality and brand, corks can be up to three times as expensive as screw caps, which can drive up the final price of the wine. At its simplest, an agglomerated stopper is like a cork-particle board, where granulated cork dust is bound together tightly by glue or a plant-based binder and pressure.
Some agglomerated corks should only be used with wines destined to be consumed young as they tend to break down more quickly. But other more premium stoppers stand the test of time. One leading micro-agglomerated cork producer, French-based company Diam, makes corks that are free from TCA, impart no flavor, and control the level of oxygen released into the wine.
This consistency makes them an attractive choice for many cork-loving winemakers. Agglomerated corks should only be used with wines destined to be consumed young as they tend to break down more quickly.
Cork producer Amorim suggests wines sealed with these composite closures be consumed within six months of bottling, though premium options do exist that allow for longer aging. Made from medium-grade natural cork, the crevices in these closures are filled in with fine cork powder.
It gives the cork a softer texture and smoother exit out of the bottle. Wines can age up to a few years under colmated cork. When two or more pieces of cork are glued together. Examples include Champagne corks, which expand upon removal and cannot be placed back into the bottle. Other producers also affix discs of natural cork to the ends of agglomerated cork in still-wine enclosures, in order to increase durability.
After centuries of unrivaled wine stopper bliss, an unassuming aluminum cap came along and, well, screwed up everything for the humble cork.
The Aussies are to blame for stirring the pot. In , Peter Wall, former director of South Australian winery Yalumba , became fed up with the number of tainted corks in circulation.
He commissioned a French company to develop an alternative closure. Forty-plus years later, screw caps are the closure of choice for the majority of Australian and New Zealand producers, across all styles and price points.
TCA, the taint that affects so many wines under natural cork, is almost nonexistent under screw cap. Screw caps can vary in price, depending on quality. Easy to open. Screw caps open with a simple twist of the wrist. Negative environmental impacts. Screw caps are made from aluminum, which is often produced from a strip-mined ore called bauxite. Processing aluminum can be a dirty process, negatively impacting the air and water and generating about 70 million tons of waste annually.
Their plastic liners, if not removed, can also make recycling impossible. Some, like the California Office of Environmental Health Hazard Assessment, also consider it to pose possible health risks.
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