Saturday, November 10, 2007

Closures. Just thoughts.

Closures are, arguably, the single most important component to protect the health and consistency of a wine after bottling. Natural cork, technical / agglomerated corks, synthetic corks, screwcaps and glass stoppers are the most common types of closures. New alternatives like Zork, and alternatives to the standard 750ml glass bottle are frequently entering the marketplace, and are gaining consumer acceptance. Why do we need an alternative to natural cork? Cork taint, Cost, Supply.
Cork taint costs the wine industry an estimated $10 billion dollars a year. Statistics show that anywhere from 5 to 7% of all wine is “corky”. Corky wines exhibit a wet cardboard aroma and flavor profile caused by a wine’s direct contact with a chemical compound called TCA (2, 4, 6 Trichloroanisole). TCA produces off aromas, but is completely harmless. TCA is the result of chlorine/chlorphenols coming into contact with mold or other microorganisms/bacteria. Chlorphenol is an industrial pollutant that is found in pestisides and wood preservatives and is absorbed by cork bark. Chlorphenol can also be produced by sanitizing corks with bleach at the cork factory. Molds may be airborne or originally present in raw cork bark, in wood used for barrels or barrel racks, tanks, scaffolding, walls, stairs, pallets, cardboard boxes, or other many other types of winery equipment or facilities. When chlorphenols mix with fungi you get TCA. If TCA infects the winery itself (not just a batch of corks), equipment and barrels must be thrown out and replaced. And because TCA can be airborne it’s difficult to eradicate. Most wineries are not infected with TCA and the majority of problems with cork taint actually come from the cork supplier. In order to reduce the risk of cork taint, reputable cork suppliers no longer sanitize cork bark with chlorine, but use hot water baths, steam/ethanol treatment and/or peroxide bleaching.
“The problem with TCA is that it is incredibly potent: most people can detect it at concentrations as low as 5 parts per trillion, which makes it hard to eradicate. To give you a better idea of this figure, it’s equivalent to one second in 64 centuries.” - Jamie Goode, “The Science of Wine”

Natural corks are made from the bark of a specific species of oak tree (Quercus suber). The first harvest of cork cannot occur until the tree is 25 years old. But cork from the first harvest is not suitable for making wine corks, it is instead used for industrial purposes or cork flooring like we have at aoc. It’s actually not suitable to be made into a bottle closure until the 3rd harvest when the tree is 52 years old! These trees are largely grown in the Iberian forests in Portugal, but can be found in other regions in the Western Mediterranean (Spain, Algeria, Italy, France, Morocco.) To make cork, trees are not cut down, but instead are stripped from their outer bark once every 9 years. The bark is allowed to regenerate, making natural corks a renewable (and biodegradable) source.

Natural cork is an excellent wine closure because it is elastic and compressible, conforming to exactly fit the neck of a bottle. But as a natural product, they are also variable and may possibly allow too much oxygen to come into contact with the wine.

The main argument for using natural cork is that of tradition. People prefer the look, feel and ceremony of natural cork. Cork suppliers also contest that cork forests are an important environmental area for several endangered species. In other words, if cork falls out of favor with wine drinkers, the forests could be torn down for use in another industry and these animals would lose their habitat. Therefore, every time you have a corked wine, consider it a donation to the endangered species of the Iberian forests.

Corks can cost anywhere from .20 cents to $1.50 a piece depending on quality.

Synthetic corks are made from plastic and are intended for wines that will be drunk within 18 months of purchase. Synthetic corks are showing more and problems through time. Unlike natural cork, synthetic corks do not expand to fill the space in the neck of the bottle after bottling. If there is not an absolutely perfect fit, the wine is exposed to approximately .001cc of oxygen everyday, where natural corks and screwcaps show less than .0001cc exposure per day. That means wines closed with synthetic corks are subject to premature ageing and browning when compared to other types of closures. Also, though this has not been scientifically proven, some people have said that synthetic closures can impart a “plasticy” taste to wine. They are often difficult to extract from the bottle and are even more difficult to re-cork a bottle with.

Synthetic corks cost .08 to.09 cents a piece.

Screwcaps: (or ROTE aka Roll on Tamper Evident) “the leading competitor to corks in terms of performance, if not yet usage.” OCW. The major breakthrough for screwcaps was in 2000 when Riesling producers in Clare Valley, Australia came together to do purchase a large quantitiy of bottles appropriate for crewcaps (over 250,000) in over to protect their wine from furthur damage by TCA taint. Just 4 years later over 200 million bottles were screwcapped in Australia. In 2001 The New Zealand Screwcap Inititative followed suit and by 2004 over 70% of wines from NZ were screwcapped (In 2001, it was only 1%).

Screwcaps provide the tightest seal for wine, protecting it from oxygen. Unfortunately, many people feel that because of this quality, screwcaps are not suitable for age worthy reds. In other words, they are almost too good of a closure. Many winemakers and experts time and this contact with oxygen allows a wine to become more complex over time. However, at the moment there is no scientific data that supports this. More research needs to be done to determine if screwcaps are a viable alternative for wines that benefit from bottle age. In my opinion they are our best alternative to natural corks. A closure trial by the Australian Wine Research Institute showed that screwcaps retained the highest levels of sulfur dioxide (SO2) in wine over a 12 month period, with natural corks coming in 2nd place and synthetic corks last. SO2 is one of the most important tools in making and bottling wine. It acts as a preservative to retain freshness, maintain fruit aromas and helps to keep wine from browning/oxidizing over time. The study did show that some bottles developed a rubber-like aroma over a 12-month period that did not occur in the synthetic or natural cork bottles.

A screwcap is made of an aluminum alloy cap attached to a sleeve and a liner of polyethylene wadding. A variety of liners are available. Some liners are now produced with a tin layer and a polyethylene layer, overlaid by PVDC (Saranex is the brand name) film. The PVDC film ensures that the wine does not come into contact with aluminum. If a liner does not have a layer of tin foil it will allow a slight ingress of oxygen which isn’t thought to be suitable for long term aging. Tin-Saranex liners are reported to hold up against the highest quality corks. Alcoas’s Stelvin is the best known brand. Stelvin, Stelvin +, Stelvin Lux and Stelvin Lux + provide these options.

Pros: 1) Aromatic freshness is preserved 2) Bottle ageing for both red and whites seem to be ok if the appropriate liner is used 3) Less bottle variation 4) Easy opening and closing 5) TCA free 6) less expensive
Cons: 1) acceptance by some consumers 2) suitability for aging is still in debate, the maturation process is not understood, is it aerobic or anaerobic?

Ruffino is now marketing three wines under screwcap. Lumina Pinot Grigio/ Libaio Chardonnay/ Fonte al Sole Sangiovese. Interesting stats for the US market:
1) screwcaps are now $200 million in US scanning channels.
2) now includes 505 items up from 330 a year ago.
3) market share is now 4.0% up from 2.7%.
4) average unit price is relatively high at $9.02 up from $8.64.
5) growing rapidly in in over $9 segments at about 13-16% per year.
6) all of above being driven by imports where market share is 7.7% (2.3% domestic share).

Glass Stoppers (also called Vino-Lok): They are beautiful, elegant, fit tightly and are easy to extract and replace. They are the closure of choice for many German Rieslings, but have yet to undergo comparative trials with other closures. Vino-Lok is a glass cap with an ethylene-vinyl acetate aka plastic rubber sealing ring.

1 comment:

Anonymous said...

Great informative Blog, however I must correct you on the manufacturer of Stelvin capsules, Alcan (Packaging) is the manufacturer not Alcoa.
(Alcoa is one of Alcan's biggest competitors)
Also Saranex is a three layered film made up of PE-PVDC-PE, and in fact is not part of a Saran-Tin Liner. Saran-Tin liners are made up of EPE-SN-PVDC, (Expanded Polyethylene(foam), a layer of Tin and a layer of PVDC film).
Saranex is however used as a coating on another common screwcap liner utilised for wines (which is commonly called a "Saranex Liner"), this liner is made up of Expanded polyethylene coated on both sides with a layer of Saranex. These liners have a much shorter shelf life than Saran-tin liners.
Saran-Tin liners can be easily identified by the silver colour (Tin) on one side, compared to white on both sides on Saranex.