When determining if the glass bottle with a natural cork is the best container for wine, the principle consideration must be the nature of the wine in question. The appropriateness of a wine’s container will vary according to the style of the wine, local legislation, the tradition of the region of production, and the value of the wine, as well as customer expectations in the destination market. For the purposes of this paper, glass bottles will be of any format and natural cork will also include granulated corks. Employing examples from high-volume, entry-level producers and those producing more modest quantities at a premium price, this paper will consider when a glass bottle with a natural cork is the best container for wine and when an alternative is more appropriate.
Glass bottles with a natural cork closure are still the chosen container combination for many wine producers around the world. However, legislation and tradition often influence the packaging of a wine. Pierre Péters bottles its range of Blanc de Blancs Champagnes in glass bottles (of varying formats) closed with a mushroom cork due to the laws governing AOC Champagne. Historic South Africa sweet wine producer Klein Constantia closes its wines in an 18th-century-style glass bottle with a cork due to the tradition of the property, not because of the legal requirement to do so.
Similarly, in its domestic market of Spain, Miguel Torres places most of its wines in glass bottles with natural corks as, according to Mireia Torres Maczassek, Spanish consumers are largely resistant to an alternative combination, even with entry-level wines retailing at €7 to 10.
Yet there are also technical considerations beyond obligations to the law, regional tradition, and consumer expectations that determine whether a glass bottle closed with a natural cork is the best container for wine.
High-quality corks possess a roughly similar, though discernibly different, oxygen transmission rate (OTR) to the least permeable saran/tin liners inside screwcaps. Though both natural corks and saran/tin liners can have dramatically varied OTR, the Australian Wine Research Institute found that the OTR of a good natural long cork and that of the best saran/tin liners is approximately the same: 0.0002 ppm versus 0.0001 ppm per day of oxygen. This performance has meant that many premium wine producers around the world put their products in glass bottles and close them with a cork, as is the case with Penfolds Grange, which recognizes the benefits attributed to slow oxygen ingress through the cork. This process develops flavor compounds and polymerizes tannins. In short, it beneficially evolves the wine and, at the same time, preserves the traditional high-quality appearance of the packaging.
However, the same might be said of screwcap technology. Acceptance of screwcap closures to replicate the benefits of a long cork OTR in top-flight wines is gaining traction. This is happening not only in Australia, where the great majority of top wines are closed under Stelvin, but also in traditional and classic Old World winemaking regions such as Bordeaux. Indeed, Château Margaux is conducting long-term (20-year) OTR trials on the same vintages closed under traditional cork, agglomerate corks, and Stelvin.
Some producers bridge the divide between glass bottles closed with natural cork and other container/closure combinations. Louis Jadot in Burgundy places its top wines in a traditional duo of glass bottle and a natural cork, keeping with the expectations of consumers of such wines. However, Louis Jadot bottles many of its entry-level white wines in lightweight, 450-gram glass bottles closed with a Saranex screwcap. This assures cheaper packaging and continuity of style at the low-cost, high-volume end of the brand’s production.
Many wines are best contained in alternative packaging due to cost, image, OTR, the risk of cork taint (2,4,6-Trichloroanisole, or TCA), weight, and recyclability. For La Riojana in Argentina, the most appropriate container for their Fair & Square range of fair trade wines, destined for sale in Sweden, is Tetra Pak. These are wines that retail at €6 to 7, where a glass bottle and natural cork would make the wine less commercially viable due to their expense. Also, for continuity of style and quality, one-liter Tetra Paks are readily embraced by experimenting wine consumers, as they are modern in appearance, are readily recyclable in markets such as Sweden, and possess a good OTR for at least 12 months. Contemporary packaging considers points of consumption, too, with lightweight pouches and cans proving highly appropriate for entry-level wines sold at sporting venues where glass bottles might otherwise be illegal.
At the low-cost, high-volume end of the market, other container combinations are popular. Joseph Mellot bottles most of its French Vin de Pays in 55-gram Polyethylene terephthalate (PET) bottles closed with a screwcap. These are cheap to produce, which is appropriate for the high-volume, less-expensive wines that they contain. They offer 24-month resistance against oxygen ingress, as they contain an oxygen barrier and scavenger, they do not break as easily as glass bottles, they are easy to recycle, and—importantly with the very large volumes moved around the world, particularly on airliners—they are light and therefore cheaper and cleaner to transport.
Nomacorc produces non-cork closures with a range of OTRs, avoiding the taint risk associated with natural corks. The least permeable closure offered is promised to age red wine for up to 25 years. Generally, however, the OTR of synthetic “corks” isn’t as good as better-quality natural corks or saran/tin liner options, as they lack elasticity and proper accretion to the bottle, with the result that oxygen rapidly enters around the closure.
Vinolok glass closures, in conjunction with a specially milled glass bottle and a DuPont Elvax sealant, are evident in Austria and Germany. Salomon Undhof, maker of premium Riesling and Grüner Veltliner in Austria’s Kremstal region, employs the Vinolok glass closure across its ranges. Though an expensive proposition, this removes the risk of cork taint and permits the slow oxygen ingress equivalent to the best corks and screwcaps.
Some red wine producers perceive the slow evolution of wines closed under Vinolok to be advantageous. Stephen Henschke was the first winemaker in Australia to bottle under Vinolok back in 2011, having bottled his iconic Hill of Grace Shiraz under screwcap for five years previously. He just prefers the look and feel of Vinolok.
The glass bottle possesses a traditional character and offers an impervious barrier to oxygen as well as an excellent ultraviolet light resistance. But not all producers are happy with the cork taint risk and variable oxygen transmission rate of the natural cork. Felton Road in New Zealand’s Central Otago is typical of a high-value, low-volume producer that has run trials on its own wines under cork and under screwcap and found the reduction in cork taint under screwcap a compelling reason to convert. The entire range of wines has been closed under screwcap for the last 12 years.
To avoid TCA, some producers are bottling their wines in glass bottles closed with agglomerated cork designed to be free from TCA. Those developed by Diam go through a cleaning process using supercritical CO2 that removes aroma compounds, including TCA. Diam offers different grades of product with varying levels of permeability. They can be cheap and particularly attractive to producers of value wines, such as Argento in Argentina, but their more expensive products are employed by Alsace’s Hugel on their grand cru range of wines. Due to its low OTR, the Diam 30 guarantees to perform faultlessly for 30 years.
Since January 2017, Amorim has offered TCA-free corks, tested using rapid gas chromatography to ensure that the level of TCA is below human threshold. While these corks are more expensive, and therefore not appropriate for low-cost wines, it is expected that all cork companies will soon be using this technology to effectively eliminate cork taint.
For wines designed to be sold in high volumes for affordable price and to be consumed soon after purchase, glass bottles closed with a natural cork do not offer the best combination for consumers wishing to buy wine cheaply and in a large format. Bag-in-box is cheap to produce, the wine can be bulk-transported, and the boxes can be filled near or in the country of sale. Much generic wine is sold in Italian supermarkets this way, and volume-based global brands such as Jacob’s Creek are available in bag-in-box in multiple markets around the world. Furthermore, bag-in-box is relatively clean to produce and possesses a much lower carbon footprint than glass, given the equivalent volume of wine.
Despite the sustainable credentials of natural cork (versus the poorer production credentials of aluminum screwcaps and cans), green glass is hard to recycle, as it is barely used for any purpose other than for the manufacture of wine bottles. It is expensive to produce and possesses a large carbon footprint given how heavy it is to transport over long distances. Alternative containers such as PET, Tetra Pak, pouches, and bag-in-box are proving easier to recycle, with Scandinavian countries leading the way.
The glass bottle with a natural cork is not the best container for all wine. Due to legislation in some regions it is, however, the only container for wine. It is still the preferred option for high-value wines from classic Old and many New World wine producers, though this is increasingly being challenged, and is the expected packaging among more traditional consumers. However, with entry-level wines, glass and cork are an expensive combination in a market with low margins. The natural cork is associated with an erratic OTR, and the specter of cork taint is ever-present. For those wishing to preserve the style of their wine, alternative containers offer the flexibility of larger formats, cheaper packaging, protection against cork taint, a modern image, and the option of a traditional glass bottle with an alternative closure, as well as the recycling advantages of modern materials.
Hello Demetri Walters MW, what will be the key determine factors for producer's to choose specific method? Does OTR, Cork Taint concerns, and Price plays more dominant influence than Sustainability, Aesthetic, and Tradition?
In response to your questions...you've asked a lot of a short essay! In brief: OTRs. Rather a big question for me to answer here. I don't have up-to-date figures that would be meaningful as it's a huge topic. Costs: cheaper agglomerate cork and some synthetics are just a few euro cents per unit. Top natural long corks around 50 euro cents or more. Screw caps are generally 1/2 the price of a good cork or even a 1/3. Their CO2 footprint is much larger though. Cork producers, if verticalised from tree to cork, can have a negative footprint. BIB is generally much cheaper and has a much lower CO2 footprint than bottles. Possibly around a quarter of the price per 75cl unit. In brief... DW
William, apologies for the VERY overdue response. I didn't see your questions until recently. I've adjusted my settings.
Great article, Demetri. - I wish there was more detail each time you talk about OTRs of different closures, (typical ranges, exact ranges of all mentioned products). How do specific numbers correlate with shelf life.- For carbon footprint - also more detail (by how much is plastic lower cradle to grave). - You mention BIB's advantage as bottleable in the country of sale after bulk shipping, but that could be (and is) done with bottled wine, too.- More detail into price comparisons between the options (price per unit at a given volume order, not just who uses what) would be extremely helpful for the fellow students.