CLOSURES: Something in the Air

The closures topic has moved away from the natural, screwcap or synthetic debate, and now focuses on oxygen transmission rates, writes Jamie Goode

It wasn’t so long ago that closures was the hot topic in the wine industry. But responses to questions on the subject from experts in the field are all similarly dismissive. “Closures all seems a little last year now … or last decade,” remarks technical expert Richard Gibson, director, Scorpex Wine Services. And Kiwi winemaker Michael Brajkovich reports: “The New Zealand Screwcap Initiative has had very little activity over the last year, and the emphasis will now be on the International Screwcap Initiative, although there has been very little activity there of late.”
So how is it that a topic that used to get people’s blood boiling has now become so uncontroversial as to no longer be newsworthy? There are several potential explanations. First, the debate has moved away from the issue of taint – it’s widely accepted that natural cork carries with it a certain risk. “I think there is a greater understanding of closure risks and benefits,” says Gibson. Instead, the current key debate is about oxygen transmission levels, and how these might effect wine development, which is quite technical and less inflammatory. Second, there is now much more familiarity with and acceptance of alternative closures generally. Third, people might just have become bored with the whole topic – after all, a lot has been written about it.
But this closures apathy doesn’t mean that it isn’t still a vital issue for the wine business; nor does it mean that there isn’t any progress. This brief review is an attempt to characterise the current state of play.

Overall, the global closures market is estimated to be around 17 billion units annually. Of these, some 4bn synthetic corks are used each year and around 1.5bn screwcaps, with the balance being made up of natural cork and closures based on it, such as agglomerates and technical corks. Other alternative closures still have quite a small market presence. These figures may surprise some readers: while screwcaps have a prominent position in some markets (notably New Zealand, Australia and the UK), they are not widely accepted in others, and so still lag some way behind synthetics.

Natural cork
Cork remains the dominant closure for bottled wine, but while there is continued strong demand for premium natural cork, lower grade cork and products such as agglomerate corks are losing ground to alternative closures. “Cork that has not been treated to remove TCA has a limited lifespan in markets where quality is critical,” predicts Gibson. “Managing risk of cork taint by batch testing (using sensory analysis or instruments) cannot guarantee the quality of individual bottles.” This is borne out by the results of the faults clinic at the International Wine Challenge (IWC) in 2007. Although the 2007 figures are still provisional, IWC chair Sam Harrop MW said this year that 3.3% of cork-sealed bottles showed taint, which is slightly up on the 2006 figure of 2.9%.
Natural cork-based closures treated to remove TCA show promise, particularly in markets where alternatives to cork are not readily accepted. Three versions of Oeneo’s TCA-free Diam are now available: Diam 1, 3 and 5, offering different price levels, transmission levels and guaranteed shelf lives (two, five and 10 years, respectively). Diam’s Mytic, a taint-free cork-based sparkling wine closure, is proving extremely popular with Champagne producers. Another product, ProCork, which consists of a five-layer membrane attached to each end of a chamfered natural cork, is gaining ground with producers who are committed to natural cork but want to avoid taint issues. “ProCork has gone through a huge expansion in the last 18 months,” reports director Gregor Christie. “We have grown fourfold.” ProCork started out in Australia, but has now shifted all its production to its factory in Portugal. “Our growth in France and Italy has been better than we experienced in Australia,” says Christie. “On what we see in Europe, there is a very strong demand for good quality natural cork, but cheap natural cork is definitely out of favour because the fault rate is too high.”

Screwcaps
Screwcaps continue to dominate some markets, but struggle in others. “The major bottle supplier here tells me they reckon that screwcaps account for 90-95% of New Zealand’s total bottled wine production,” says Brajkovich. And “The Australian wine market will be 70% screwcap soon, if it isn’t already,” reckons Christie. “The big change is that traditional European countries are much more open than before,” says Anne Seznec, marketing manager for Guala Closures Group, an Italian company that makes the Global Cap range of screwcaps. “We think people will soon understand that screwcaps are not just for cheap products.” Seznec estimates that the global screwcap market is growing 15% per year. Evidence that times are changing is provided by the fact that Portuguese producer Champalimaud (which owns Quinta do Côtto) has switched to screwcap – unthinkable a few years ago – and has not lost a single customer as a result. However, Seznec reports that the USA is still proving a tough market to convince on the merits of screwcaps. Global Cap has established factories for screwcap manufacture in India and China, which it sees as promising markets.

“The big interest in PET bottles for wine will be another big change,” says Franco Cocchiaro of Guala, who reckons this will be an opportunity for screwcaps, which are the closure used to seal these bottles.
To their standard screwcap  Divinum, Global Cap has added a new product WAK, which looks more like a traditional capsule, but still uses the same BVS finish bottle type that is used for other screwcaps. Similarly, Alcan has introduced Stelvin Lux, a screwcap with an internal thread that looks similar to a traditional capsule from the outside.
One point that must be emphasised is that screwcaps aren’t the closure. They are just a means of holding the sealing medium, the screwcap liner, in close apposition to the rim of the bottle. In discussions about screwcaps, it’s important to be precise about the liner type, because these determine the closure’s properties. Currently two liners are available for wine: “saran/tin” and “saranex only”. These are used by all screwcap manufacturers. The former has a metal layer which allows very little oxygen transmission; the latter allows a bit more. The tin/saran liner is the one that is used almost exclusively by producers in Australia and New Zealand, while many European producers have opted for the saranex-only liner.
This is because working with the saran/tin liner is technically challenging for winemakers: it’s a bit like trying to land a plane on a very short runway – everything has to be right. This is because of some important post-bottling chemistry that takes place in wines where there is very little oxygen ingress that can lead to problems with sulphur compound chemistry, known as reduction, if the wine isn’t just right at bottling. It’s a complex subject, but in short, in difficult conditions during fermentation, yeasts can produce sulphur compounds that are particularly smelly at relatively low concentrations. The danger comes when wines that otherwise seem quite clean at bottling undergo changes after bottling, whereby less smelly versions of these sulphur compounds change to more smelly versions under conditions of very low oxygen ingress. Good winemakers will therefore aim at clean ferments, making sure, as far as is possible, that none of these problem sulphur compounds are present before bottling if they are using tin-lined screwcaps. Sam Harrop MW reports that 2.6% of screwcap-sealed wines showed reduction issues in the 2007 International Wine Challenge, up from 2006. However, it should be pointed out that many consumers would not notice reduction in their wines, and it is certainly nothing like as significant an issue as cork taint. And not all winemakers see the low gas transmission properties of the saran/tin liners as a problem. “From the last six years’ experience at Kumeu River, I can say that we are very happy with saran/tin liners,” says Brajkovich.

Still, there is a need for a wider range of screwcap liners, and many companies are in the process of developing these. “We are working on new liners, but it is a delicate market,” says Global Cap’s Cocchiara. “There are two liners that are well proved through many years’ use. But we have found an interesting new material, which is a plastic polymer with different oxygen permeabilities, and in collaboration with the University of Turin we may have a new liner by the end of the year.” ProCork is also working on barrier films suitable for other closures in the beverage market: could one of these be a screwcap liner?

Synthetics
Synthetic (plastic) corks, have struggled with an image problem in the UK of late, but worldwide sales are still growing. The leading player is Nomacorc, which has a dominant position with 45% of the synthetic category. “We grew another 25% in sales in 2007,” reports Malcolm Thompson, vice president of quality and technology at Nomacorc, “which is remarkable considering we had a sizeable base of 1.5bn units.” This brings Nomacorc’s sales up to 1.8bn in 2007, and he’s projecting similar growth for 2008. “In Europe things are exploding, with Italy a particularly exciting market.” In 2007 the firm opened a plant in China. “It will become one of the largest consumer markets in the next five to 10 years,” predicts Thompson. “The wine market in China is currently 600 million litres and is growing at 20% per year.”

But not all synthetics are equal. “Synthetics that are based on good technology are those companies that are experiencing growth, but there are lots of poor products in the marketplace,” says Thompson, “and we don’t want to be grouped with them.”  
Future directions
It’s now clear that the key property of a closure, alongside practical considerations such as cost and market acceptance, is its oxygen transmission rate (OTR). “It’s not about screwcap, natural cork or synthetic,” says  Thompson, “it’s about OTR.” The big problem facing the wine industry now is knowing exactly what closure OTR is required for specific wine types: if this information were known, closures with particular OTRs could be matched to wine type.
With this data void in mind, Nomacorc has recently begun research initiatives with University of California, Davis (USA), INRA (France) and the Australian Wine Research Institute to look at the role of oxygen in post-bottling wine chemistry. “Tell us what OTR you want and we can deliver it,” says Thompson, “but the problem is we don’t know what OTR is needed.” The studies will use a range of wines and winemaking processes and look at the effects of different OTR levels in wine development. In California a Cabernet and Chardonnay with four different winemaking regimes will be studied, with the same process repeated using different varieties in France and Australia. “We hope to be in a position to design closures that will have optimum oxygen transmission for the wine style,” says Thompson.

It is likely that in the future there will be closure companies that can offer winemakers a portfolio of closures at different OTR levels, which, with the appropriate knowledge base, can be matched to wine type, thus extending winemaking beyond bottling, such that consumers are offered wines that show their best at point of consumption.

 © db February 2008