The author, Berenice Barker-Kenny, graduated as a Cape Wine Master with her thesis concerning closures in the Wine Industry in 2004. She's also a Diploma II Graduate from the Cape Wine Academy (Johannesburg) and has been variously involved with the South African wine industry for several years. We are grateful for her permission to reproduce this abridged version of her comprehensive study of "Bottle Closures in the Wine Industry".
The closure issue is highlighted most profoundly by the debate which pits defenders of tradition against practically minded dispassionate people who view the selection of closure in the clearest light - and the choice of screw caps provides an arena in which to do it. Screw cap refers to any metal cap which is capped over a bottle top; the term Stelvin is used nowadays interchangeably but should specifically refer to the patented closure of Pechiney, France and the term Savin cap to refer to the product of MCG Industries in South Africa.
Dan Rylands of Barnsley in the United Kingdom patented the screw cap on August 10th 1889. Searches for references as to the first time use of screw caps for wine, yielded no information. However, the Whiskey Bottle website details 'the replaceable cork and self opening bottle' as being part of the slogan of Teacher's Highland Cream in the early 1900's. A screw cap was introduced in 1926 by White Horse Distillers, an innovation which doubled sales in six months. Until 1913 whiskey bottles were sealed with cork.
Over the last half a century screw caps have been used extensively in the wine industry. The first seals were found to be unsatisfactory and it was not until the introduction of the Stelvin closure -developed in the late 1950's by La Bouchage Mecanique, a registered trademark of French manufacturer Pea-Pechiney -that the seal came to be recognised as a quality product. The long skirted Stelvin closure was created specifically for wine bottles and was developed from the Stelcap, which used to have cork liner.
At the time of writing, there were numerous internet surveys which were being undertaken to disprove the Wine Intelligence closure survey which proclaimed that 'cork is king'. A survey was commissioned by Villa Maria in New Zealand and their conclusion as to consumers' views on screw caps was vastly different to Wine Intelligence's findings. Tickbox.net undertook the research in early September 2003 and yielded results which showed a considerable acceptance of the closure by 2702 respondents, 64.4% of them had bought screw capped wine or were prepared to do so. (Villa Maria had decided in 2002 to close all their production with screw caps).
Producers of alternative closures are each trying to prove that their product is being accepted by various niche markets and so could be the rightful successor to natural cork. There is undoubted acceptance of the closure within specific target markets, but the question to be posed is whether the move towards screw caps is a production or marketing driven issue. Is it truly the consumer who is driving the screw cap revolution or is it the wine makers and closure producers or indeed the retailers who are motivating it?
2. A BRAVE NEW CLOSURE
The metal screw cap with the appropriate liner, is a barrier which air can not diffuse through. (11) Therefore ageing reactions which are dependant on oxygen will not occur. Vernon Singleton (UC Davis Professor Emeritus) a leading international authority on wine ageing, states that the chemical reactions responsible for bottle ageing are not oxygen dependant, implying that the alternative closures will not interfere with bottle ageing. His opinion is that bottle ageing does not occur unless there is considerable protection from oxygen. (14)
The concept of the passage of air and micro-oxygenation that occurs is one which certainly has two very distinctive camps of winemakers. It is possibly this conflict which could be the brake on a wider acceptance of the screw cap. The traditionalists, both consumer and winemaker, with fervent beliefs that bottle ageing is only possible with a cork, are pitted against the modernists, seeking a closure which preserves the wine and allows the numerous and varied chemical reactions to occur in the absence of air. (The latter mentioned winemakers dismiss the notion that miniscule amounts of oxygen move through the cork into the wine to enable bottle maturation).
The most extreme measure taken to date by any wine producer was that of Napa Valley's Plumpjack who bottled 300 cases (half) of their reserve Cabernet Sauvignon 1997 under a screw cap - the wine sold for US $ 135 per bottle. This move received a great deal of attention, not only in view of its statement on closures for age-worthy reds, but also to illustrate the extent that producers will go to, to register their displeasure towards natural cork. Plumpjack, not unlike several South African producers, however have not totally abandoned cork altogether.
South African producer, Vergelegen, sent a very strong message into the local wine trade when 500 cases of the 2002 Sauvignon Blanc were bottled with a Stelvin closure. Andre van Rensburg is quite vehement on the topic of the unacceptable level of poor quality corks. The winery had to tolerate numerous complaints pertaining to the high incidence of TCA infected corks in the bottles of the 1999 Vergelegen Red. These culminated in the withdrawing of the product from the market and the search for alternatives was embarked upon.
Any producer undertaking such a dramatic step has to think about the marketing ramifications as screw caps are perceived by many consumers as cheapening a brand. A considerable concern expressed by Eddie Turner (Group Marketing Manager - Amfarms) especially in light of the recently published Wine Intelligence survey which clearly revealed the consumer view of screw caps being the type of closure used on inferior beverage products. An opinion also expressed by Andries Burger, winemaker at Paul Cluver Estate, that only when the consumer market starts to demand the closure, would they consider using it. Consumer perceptions and brand building are integral in the Estate's long term planning -adoption of an alternative would only ever be undertaken after very careful and no doubt serious deliberation; as well as definitive marketing research.
3. TECHNICAL SPECIFICATIONS
The outer, visible layer of the screw cap is made from an aluminium based alloy. Inside of the twist top is a multi layered liner. The modern screw cap differs from the original Stelcap only in the wadding material. Essentially there are coverings over the expanded polyethylene liner - a round disc shaped item which is punched into the closure during the manufacturing process. This disc lends the elastic resilience to maintain the liner's compression. It is not the aluminium cap which provides the much sought after impermeable gas barrier but rather a film of tin foil less than a 15th of a millimetre thick. This is separated from the wine by a very thin film of inert polyvinyl denachloride - PVDC. PVDC is a solid plastic polymer. Solid, in that it is not a gas filled puffed polymer. It is an un-pigmented pre-shrunk film which is laminated to the tin of the capsule. Older and earlier liners had agglomerate cork on the backing; the greatest problem experienced with these early attempts was the non-recovery of the cork after pressure had been applied during capping. (11)
During the capping process the central polyethylene section of the liner is compressed over the end of the bottle and so forms the seal. Of importance is the total compatibility of the glass bottle and the screw cap to guarantee perfect capping and sealing. During the bottling process, the cap is dropped over the bottle top and the seal is formed by the capper. Two sets of rollers effectively create the thread and PP groove as is seen on the finished product. The PP groove is the horizontal groove which is rolled into the closure during the application by the 'skirt rollers', thus locking the lower portion of the closure onto the bottle. The lower section or 'skirt' of the closure stays on the neck of the bottle whilst the threaded section comes away in your hand. These rollers are set to specifications and profiled to be compatible with the finish of the bottle. Pressure is exerted from above the capper to enable the formation of the 'reform' which folds the liner around the sealing shoulder of the glass finish.
A concern to the producers wishing to follow the screw cap route, is the prohibitive cost of bottles and packaging. The cost of any glass bottle increases incrementally due to factors such as weight, style and colour of glass. The bottle lip has to be perfectly moulded to facilitate the screw cap as any deviation will result in the ineffective and improper sealing. New bottling lines have to be implemented. At significant cost, this type of commitment has to be taken seriously. Careful selection of mobile bottlers is a must. Application errors could compromise the efficacy of the seal as the film in the liners' inner part of the cap can be damaged. Packaging and handling have to be closely monitored as well. Until a year ago, there were no locally produced bottles which were suited to the Savin closure and bottles had to be imported from Saver Glass in France. However as the demand for screw caps increases, this will enable the greater selection of bottles as the local manufacturers will be obliged to provide a wider range.
Not only does careful attention have to be paid to the fill heights of the bottles, but as the bottling lines for cap closures do not allow for the pulling of a vacuum, the headspace is normally purged with an inert gas as selected by the winemaker, before capping. A fill height of 30mm at 20°C is recommended, albeit that these figures might well be altered depending on the bottle variations.
For bottling with an aluminium closure, it is recommended that the cap manufacturer is in contact with the bottle supplier so as to make necessary changes to the mould or finishes of the bottle. Ken Bode (MCG Technical Manager) stated that MCG certainly do work very closely with the bottle manufacturers to ensure that all the components are within the specification limits. Steve Bell ((MCG National Sales and Export Manger) succinctly stated that they are "the custodians of the bottle neck".
The new generation of closures have a superior feature, that of 'redraw' or 'reform'. The lack of this feature on older versions is what could have caused the wad to be lifted from the top surface of the glass, if the seal was dented. Modern capping blocks draw the aluminium outer very closely around the glass rim profile. Air gaps are thus removed which would have provided room for indentation and resulted in seal failure. This improvement makes the seal safe from external impacts, as well as increasing durability and sealing efficiency.
Pechiney, the French company which has the patent rights to Stelvin, claim that the most important part of their closure is indeed its lining, which features two layers. An elastic compressible material ensures an airtight seal and then there is the inert plastic film barrier. Stelvin guarantee their closure not to leak, that it will preserve aromas, meets food regulatory requirements, offers economy (combines cork and capsule functions) and is recyclable.
4. INTERNATIONAL APPLICATIONS OF SCREW CAPS
In the early 1960's Yalumba (Australia) released a series of premium wines bottled with the Stelvin closure. According to their sales reports, consumers did not accept the wines at the time as it was only 'cheap plonk' which was viewed as being closed by metal caps. Retrospective tastings undertaken by Yalumba reveal that the wines are still in excellent condition. Back in the 1970's Chateau Haut-Brion undertook tests over a ten year period -these initially showed that wines in screw cap bottles were no different to those under cork. The plastic film in the screw caps on the 1969 wine started hardening and breaking resulting in oxidation. The deterioration became so pronounced that the experiment was stopped. (14)
Professor Emile Peynaud went on record in the 1980's stating that screw caps are the perfect way to seal a bottle of wine. At the time of writing, the greatest proponent of a change to screw cap at retail level is Tesco - Britain's biggest supermarket group and largest wine retailer. Tesco sells well over 200 million bottles a year and began their campaign advocating screw caps when they calculated that 1 in 12 bottles was affected with TCA. They have gone from nothing under screw caps to more than 100 million such bottles, in 18 months - such is the scale and speed of their screw cap revolution.
There are various Australian and New Zealand producer trials under way, and the successful results which are released from the wineries present a compelling case for red wines under screw cap. As a greater number of red wines than ever before are appearing on shelves, an ideal opportunity is being provided for comparison. The rate of development of a capped wine is drastically reduced as is evidenced by the greater amounts of sulphur dioxide retained. These wines maintain the purity of the varietal fruit character better than cork in the opinion of Kumeu River's Michael Brajkovich (New Zealand) and Stephen Henschke of Henschke (Australia). Clare Valley winemaker, Andrew Mitchell points out that, "Old wines under screw cap are typically described as fresh. People interpret this as meaning 'not mature' but this is a different concept. These wines still have the full array of mature characters, but with life."
Only time and trial will resolve the question of long term sealing with absolute certainty. As a number of key issues are raised in respect of the role of cork and oxygen and long term maturation. Again, it is the Australians who lead the way with numerous examples of screw capped wines from a range of wine producers and whose long term cellaring have afforded the comparison options. There is hardly a negative word printed as to how well the wines showed, tasted and held out - no taint and no oxidation. Dr Bryce Rankine, one of Australia's foremost wine research scientists is quoted as having said, "I myself have very little doubt that screw caps in red wines will take off in the same way as they have in white wines. Watch the show results. My guess is that the Stelvin closure results will be superior to those of cork." (14)
Other examples of the growing use of screw caps are:
The Clare Valley Riesling Producers (Australia)
Riesling being a very aromatic and a delicately perfumed wine, is very susceptible to having its character drastically altered by the slightest concentration of cork taint. It was frustration with taint and the desire to produce a quality wine which led 15 of the premium producers of Riesling in the Clare Valley to make the biggest endorsement of all - they bottled their wines with Stelvin. A special bottle was commissioned in France for the producers and the launch slogan was 'Riesling with a twist'. To , it has been a particularly successful promotion.
Super star Italian producer Angelo Gaja has bottled his collection of library wines under screw cap. These are wines intended for future tastings. Yet he has the reputation for using the world's longest, finest and most expensive corks for the wines which he sells.
Since the early 1980's Penfolds has been testing different closures on t mighty Cabernet/Shiraz blend, Penfolds Grange. Head Grange winemaker, Peter Gago, when interviewed online by Decanter.com (www.decanter.com/nov2003) stated that the trials were provoking research as it was clear how little understanding there is of the chemical ageing of wine under the alternative closures. The wines were evolving more slowly but consistently and comprehensively. He viewed the wines under cork and screw cap as "being more or less identical - the differences being very subtle, such as ageing in a cold cellar and a very cold cellar". These are however trails pointing the way, as sulphur dioxide, aldehydes and volatile acidity levels are monitored.
In replying to why they have not taken the plunge and bottled all of their good wines under screw cap, Mr Gago replied, "Discerning consumers understand the benefits, but we can't take the risk. We don't know what screw caps will do after many decades. The polymer in the seal is said to be inert but this is only defined over a particular time frame. It may be inert for 10 years, but what about 20 or even 50? We just don't know how they will perform long term". (Penfolds offer re-corking clinics to check existing corks in bottles, often removing and resealing with a new cork. Could the same not for an option for the future with bottles being recapped -seemingly a simpler process and one which avoids the risk of taint).
Flamboyant Grahm of Bonny Doon Vineyards in Santa Cruz, California fired a powerful message to the cork producers when he staged an elaborate funeral procession and wake through the streets of New York in November 2002. Jancis Robinson delivered an elegy to cork at the faux funeral, referring to its "utter darned ridiculousness as a 21st century stopper". Grahm subsequently bottled his 2002 wines under screw caps stating that "the screw cap is a superior closure". In a daring move Bonny Doon put screw caps on all 80 000 cases of their 'Ca del Solo Big House' red and white table wines. He was one of six leading American winemakers who abandoned cork that year.
5. THE SOUTH AFRICAN PERSPECTIVE
It was as early as the 1970's that screw cap closures were highly praised by Gunter Brözel after their seemingly faultless performance on the 250ml bottlings of wine for various airlines. MCG Industries in South Africa operated under an agreement with Pechiney for the production of the Stelvin closure locally. Upon expiration of the contract, MCG registered the Savin closure. The company has a remarkable history and background having seen the screw cap through various phases in the local market. Their involvement in capping spirit products paved the way and provided the learning curves.
Savin is the screw cap closure of choice for several South African wine producers yet MCG also boast an impressive list of international customers using the product. In a personal interview with Ken Bode (MCG Technical Manager) and Steve Bell (MCG National Sales and Export Manger) the opinions expressed all centred around the sealing abilities of their product to keep the wine taint free, aromas fresher and indeed the fruit component of a wine in a more pristine condition than what cork can offer. Whilst consumer resistance and the failure of screw caps to play a more meaningful role in the wine industry, is attributed by Mr Bell to a real lack of understanding on the part of the consumer - he is tackling the education issue head on. Expressing regret that the South African Screw cap Initiative has not been as successful as the Australian and New Zealand chapters, he is undertaking coverage of the closure in life style magazines - fully aware that it will be a producer driven effort as well as a winery effort to persuade the masses that the closure is neither cheap, nor nasty. The Australian market for screw cap closed wine is estimated at 15% and is plainly attributed to consumer education. Mr Bode also noted that it was primarily the wine producers who export to the UK market who first took the step to screw cap due to the requirements specified by the European wine buyers. In their opinion, the closure has a very real future in South Africa.
Mr Bell put a humorous twist on our discussion by quoting Bob Campbell (New Zealand wine critic and Master of Wine): "Just imagine the response, if the whole wine industry had been using screw tops for generations and some bright spark popped up to tell us there was this great new thing called cork. Of course, it means that about ten percent of wine will be tainted, there will be dulled fruit flavours, musty odour problems and variation in wines as they age. But hey, it makes a great sound when you pull it out of the bottle!"
6. CHANGING THE PARADIGMS OF CELLARING
"Corks are difficult little creatures to keep happy", states Tyson Stelzer in his book, screwed for good. (14)
He continues to detail all the requirements which have to be met for proper cellaring, all of them so as to appease the cork. The rules for cellaring cork closed wines and screw capped wines differ to some extent.
The first condition to be met is that of a stable temperature in the designated cellar. Fluctuating temperatures cause the wine to expand and contract, thus resulting in pressure changes within the bottle. This leads to leaking corks and the loss of the stopper's resilience and effectiveness over time. The results from Auscap (the leading Australian cap manufacturer) have shown screw caps pressure handling capabilities to be better than cork. However it should be pointed out that no matter what the closure, it is unquestionably better for the cellar to be at lower temperatures than higher ones, as the warmer environment (above 20°C) causes the wine to develop prematurely. (14)
Screw caps have absolutely no requirement for humidity to maintain the seal; unlike natural cork. There is a very fine balance to be maintained as regards the humidity in cellaring cork closed wines. A higher humidity prevents the cork from drying out and the wine evaporating, it however also encourages peeling of labels and moulds.
Screw cap closed wines have no requirements for storage and can be kept upright as opposed to cork closed wines which have to be laid horizontally to make certain that the cork is kept moist. The early detection of a broken seal would be the only reason to position screw capped bottles down or horizontally.
The impermeable seal of the screw cap ensures that no cellar odours will be absorbed by the closure and migrate into the wine. Thus no 'off odours' will taint the screw capped wine, as is the case with corked sealed wines.
The rules for cellaring screw capped wines are not new, as the above mentioned points were featured in the 1980 Wine and Spirit Buying Guide. The report ended as such, "The conclusions thus are that Stelvin does show a superiority to cork both in its oxygen inhibiting qualities and its ability to withstand storage conditions without affecting the wine."
In most circumstances it would appear to be the winemaker having reached the proverbial of tether, pushing for the alternative. Wine consumption is certainly becoming more of a daily drinking process and as such consistency of product ought to be more important than ritual. Whilst the winemakers are understandably frustrated with natural cork, however at no time should they underestimate the cognitive effects of screw caps. Consumer education has to be undertaken to ensure that the benefits of these closures are understood and appreciated - it is not enough to assume that i the more knowledgeable client who will purchase a capped bottle and thus extrapolate that it is, anyhow, this market segment to which they are appealing.
The aim of SASI (the South African Screw cap Initiative), founded in 2002 and coordinated by Lucy Warner, was to enable an exchange of information amongst the wine producers who had opted for or were considering the closure. Much was made of the trade tastings, public discussion forums and joint marketing ventures which were to have been undertaken. Regrettably, the reluctance of producers to join and share information or joint marketing efforts has resulted in this initiative being all but dead. Certain individual producers have forged ahead with the alternative closure, highlighting in Ms Warner's opinion the apathy and total inability of the South African wine industry to work cohesively.
Screw caps can be a viable alternative to cork but until there is more data on how they perform over the long term of ageing, there will be reluctance by a greater number of winemakers to bottle and by collectors to store. Tyson Stelzer (14) however is of a very different opinion, concluding the chapter headed 'peter pan wines' he states: "Extended ageing time might well be the only criticism that screw caps prove to live up to, but is this really a criticism at all? It is universally accepted that wines that age slower, age better. The very greatest old wines have matured slowly and elegantly, maintaining some of their fruit characters. Screw caps make this possible for every bottle, ironing out flat spots in a wine's development and elongating its ultimate drinking plateau. And if it does happen to take longer to get there, well, if the cap fits, we might just have to wear it."
What is certain is that the screw cap revolution's success will be determined by the consumers. Regardless of the strength of arguments or evidence, or the drive by retailers via their wine suppliers, it remains the consumer's choice to buy it, or not.
Wine and the perfect closure indubitably have a long and bumpy road ahead. The great closure debate is one which will rage on for years to come. All producers, and indeed users of various closures are equally passionate and vehement about their products. The diverse screw cap initiatives and trials, and the ten year AWRI project should be closely watched for any surprises as these mammoth projects unfold and new data becomes available.
Natural cork might well be the corner stone of the industry today, but too many accepted standards are no longer in place having been superseded by technological innovations: 8 track cassette tapes or vinyl records by DVDs; carrier pigeons by email; passenger liners by supersonic flight -the transformations are endless. Bottle closures will change with the rapidly evolving aspects of technology and the dynamic nature of beverage products will ensure the evolution. After all, how much innovation and technological improvements are not seen in the wine industry every year with every harvest.
The author is of the opinion that there will be a niche for each closure; corks will indeed become more expensive as the research and development costs escalate in the pursuit of a taint free product. Thus their use will be limited to age worthy and premium products within most winemaker's portfolios. Synthetic closures will have their application in wines designed for early drinking and screw caps will remain the closure of choice of winemakers wanting to preserve their wines' intrinsic character at all costs. These winemakers will continue making a statement - be it a fashion or a contentious one. The quest for alternative to cork closures will undoubtedly be spearheaded by New World wine producers as upfront fruity wines are their signature.
The small metal crown cap as seen on beer, cider and alco-pop bottles has proven itself to be a reliable stopper over the years, yet it is probably the least fashionable or desirable consumer appealing closure. It does however provide for a cheap and efficient stopper and its use in sealing champagne bottles during the second fermentation phase has universal applications. Spectacularly brave would be the wine producer who ventured down this route to close mid to premium priced wines with this closure.
Ultimately it is the winemaker who makes the judgement call as to which closure he or she is prepared to place their proverbial necks on the line with, it is their name and reputation which inevitably sells the bottle. It is for this inherent reason that the alternative closure producers ought to be embarking on a more rigorous educational route to persuasion, so as to enlighten the winemaking fraternity who in turn can offer more substantial information to their ever attentive public. The screw cap producers - who have in the author's opinion the closure to take the wine industry beyond the current haranguing - certainly need to enhance their products' appeal to consumers, beyond any doubt.
The task will be to manage the transition efficiently and effectively.
| ||1.||Robinson, J: Oxford Companion to Wine, Oxford University Press 1994|
|2.||Personal interviews December 2003 Joaquim SA - Amorim and links off
| ||3.||Casey, J: Presentation at the National Conference of the International Wine Law
Association, Adelaide Australia 25-27 October 2002|
| ||4.||Wine Magazine SA November 2003|
| ||6.||www.awri.com.au/pettergodden et al:awri trials and results|
| ||7.||Apcor Survey 16-31 January 2002
| ||8.||Wine and Spirit Association Survey 2002 www.corkfacts.com/november2002|
| ||9.||Quercus Survey www.corkqc.com/tcaquercus.htm|
| ||10.||Personal interview December 2003 Paul van Dooren (GM Supremecorq SA) and
| ||11.||Personal interviews December 2003 Ken Bode and Steve
Bell (MCG Industries SA Technical Manager and MCG Industries SA
National Sales Manager) and www.nomacorc.com|
| ||12.||Personal interview January 2004 James Reid (Operations Director Western Wines)|
| ||13.||Personal interview December 2003 Johan Malan (Owner and winemaker Simonsig Family Vineyards)|
| ||14.||Stelzer, T: screwed for good - the case for screwcaps on red wines, Wine Press Brisbane Australia 2003 ISBN 0958062811|
| ||15.||Personal interviews Eddie Turner and Andre van Rensburg December 2003
(Vergelegen Marketing Director and Vergelegen winemaker)|
| ||16.||Personal interview Abrie Beeslaar December 2003 (Kanonkop winemaker)|
| ||17.||Personal interview Carolyn Barton December 2003 (Makro national wine buyer) |
| || || |
| || || ACKNOWLEDGEMENTS|
| || ||Daan Joubert for all the effort, energy, time and advice
and for getting the ball into and indeed keeping it in motion. Marilyn
Cooper, Andries Burger and Cathy White for all their
encouragement. The Barns family for all the cheering on to "just do it"
and for making available to me the most fabulous of environments,
Mischa Estate, in which to work on this document. My parental
unit who supported me tirelessly.....even from a distance. Steve Bell and
Ken Bode - MCG Industries SA -not only for their help and
assistance, but more to acknowledge the lessons in how to open a screw
capped bottle correctly! Margie, Heidi and Junel, my longsuffering
study group, what awesome friendships have resulted. I've yet
to experience such camaraderie - albeit that a bottle of bubbles was
always in reach to ease the agony!|