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  • April 5, 2014
  • Why Screw Caps?

  • by Lars Carlberg

screw_caps_immich_gruenhausIn the Mosel region, aluminum screw caps have become extremely popular over the last several years, especially for inexpensive wines meant for early consumption, such as a Gutsriesling, or a basic "Estate Riesling." In fact, it is increasingly rare to find producers using natural corks for their entry-level bottlings.

Others bottle all their wines under screw cap. This seems more logical if the fear is corky wines. Why risk a corked bottle for the most expensive wines? Many winemakers, however, feel that screw caps are still unproven for long-term cellaring.

So why have screw caps become so popular on the Mosel? One important factor is rising consumer acceptance. In fact, many German restaurants now prefer screw caps.

Screw caps are said to be neutral from an organoleptic point of view. Yet the main argument for using screw caps and not natural corks is to avoid the pesky cork taint, a chemical compound known as TCA (2,4,6-trichloroanisole), which gives wine at extremely low concentrations a musty flavor, but, in its more subtle form, can make the bottle of wine just seem muted or "off."

According to Jamie Goode's Science of Wine (University of California Press, 2005), TCA comes from the "interaction between microbial metabolites and chlorine in the environment." He points out, too, that "TCA isn't confined to corks, nor is it the only compound responsible for musty aromas." Other food products have cork taint, and both TeCA (2,3,4,6-tetrachloroanisole) and TBA (2,4,6-tribromoanisole) can also come from corks and give off musty aromas in wine.

Corks often get the sole blame for TCA. But TCA, like TeCA and TBA, can come from other sources in the winery, such as wooden pallets or cardboard boxes. In other words, a wine fermented in stainless-steel vats and bottled under a screw-cap closure can have cork taint. Chemists from the Dienstleistungszentrum Ländlicher Raum (DLR) in Rheinland-Pfalz are said to have found traces of TBA even in wine filters, in addition to screw caps.

The other problem associated with cork is sporadic oxidation when the closure is not tight enough. In contrast to natural cork, a properly fitted screw cap (with a tin foil layer) is almost airtight to a fault, and there's less variability than cork. Yet not all screw caps are well sealed.

The following headings look at various aspects of this topic in more detail.

What's Stelvin

There are various manufacturers of screw caps. Stelvin is the most popular brand and has become a generally accepted term for this alternative wine closure. Another well-known brand is LongCap, made by Mala.

Besides the original Stelvin® wine screw cap, Stelvin® Lux has a smooth cap, which doesn’t have a visible screw thread around the sides and, thus, looks more like a capsule with a cork underneath. In the Mosel region, Dr. Siemens and van Elkan choose to use Lux. Most Mosel producers, though, prefer the original Stelvin with the visible screw thread and have their emblems printed on the top and skirt of the different-colored caps, which, in my opinion, looks better. Use of the Lux raises the question of why have a screw cap at all.

Some producers prefer an embossed logo on the top of the cap or other design options. In addition, screw-cap manufacturers, like Stelvin, come now with different types of liners, such as Saran™ Tin and Saranex™, which are inserted on the underside of the aluminum caps and offer various levels of oxygen dispersion for the aging process of wines. Saran™ Tin and Saranex™ are made to seal wines that should be consumed within three and five years, respectively.

The Origin of Screw Caps

According to the International Screwcap Initiative, screw caps have been used on wine since the late 1950s. The French company Le Bouchage Mecanique (present-day Alcan) first manufactured a screw cap, called Stelcap-vin, for Peter Wall of Yalumba in 1959. He wanted "to eradicate cork taint in his wines and preserve their freshness." According to the Yalumba website, Wall "originally approached LBM in 1964 about an alternative sealing system for wine bottles. Peter, who has since retired from Yalumba, almost single-handedly drove the development of the Stelvin closure."

Australian Consolidated Industries (ACI) acquired the manufacturing rights for screw caps in 1970 and "was renamed Stelvin for the Australian market, and trials at the ACI laboratories took place" (Goode, The Science of Wine). In 1973, Yalumba, Hardys, McWilliams, Penfolds, Seppelt, and Brown Bros & Tahbilk were involved in developing a concept and began bottling wines with a screw cap in 1976. There was consumer resistance at the time, because screw caps were deemed cheap, and many of the producers, including Yalumba, returned to natural cork. As Goode points out in his book, there were also issues with the right wadding (including agglomerated cork) and other shortcomings at the time. In 2000, Yalumba started using Stelvin again for some Rieslings, and now use screw cap for other wines as well.

In Australia's Clare Valley, Jeffrey Grosset began using screw caps in 2000 and encouraged other producers in Australia and New Zealand to do the same. He now bottles all of his wine, including Riesling, under screw cap. His book, Taming the Screw, teaches winemakers to bottle their wines under screw caps. Today, producers in Australia and New Zealand use a high percentage of screw caps.

Screw Caps for Mosel Wine

Reinhard Löwenstein, owner of Heymann-Löwenstein, in Winningen, would like to use screw caps for all his wines, but still bottles some with natural corks, as he finds resistance to screw caps in certain European markets. He doesn’t want oxygen seeping into his bottles from the outside or getting any phenol transfer. “Stelvin conserves best, it’s unfortunately still frowned upon in France, Spain, and Italy,” says Reinhard, who also feels that his wines don’t need any further oxygenation after bottling and don’t show any screw-cap reduction either. The winemaking at this address, it should be noted, is different from most Mosel producers. He prefers long skin contact and seeks must oxidation. Moreover, he bottles much later because his wines ferment and age longer in either 2,400-liter oak Doppelstück casks or large stainless-steel vats.

Besides being less oxygen permeable, a more common reason to use screw caps is economic. It's not just the frustration of having corked wines. A high-quality natural cork costs more than a screw cap. Otherwise, producers would use screw caps more on their higher-end wines. Instead, most Mosel producers put screw caps only on entry-level wines to meet price points and to avoid returned bottles on the fast-moving wines, although others justify using screw caps for the relatively simple wines meant to be consumed young, and the best are bottled with a natural cork.

At Selbach-Oster, in Zeltingen, Johannes Selbach doesn't see a big difference in price or quality between natural corks and screw caps. He is actually a proponent of screw cap, but doesn't know how his higher Prädikat wines, both dry and sweet, will age over the long haul, hence screw caps only up to Spätlese. Yet many of these basic and lower Prädikat wines, like his Zeltinger Himmelreich Kabinett halbtrocken, can age a long time.

Willi Schaefer, Schloss Lieser, and Maximin Grünhaus, among other top producers, are doing the same now. In fact, at Wwe. Dr. H. Thanisch – Erben Thanisch, the proprietor Sofia Thanisch has recently begun to bottle her basic Estate Riesling to Kabinett wines—not the Doctor Kabinett, though—under screw cap. The reason is quite simple: the less-expensive offerings are meant to be enjoyed young, and clients—particularly restaurants in Germany—are requesting screw caps more and more. They don't feel like they need to worry about cork taint, and the bottles are easier to open and close.

Other notable producers who now use screw caps for their basic wines include Ansgar Clüsserath, Fritz Haag, Dr. Wagner, Weiser-Künstler, Peter Lauer, VOLS, Zilliken, von Othegraven, von Beulwitz, Knebel, Immich-Batterieberg, and Reinhold Haart.

Respected Saar winemaker Hanno Zilliken says that screw cap is practical for short-term drinking, but he doesn’t want this closure for his long-aging “Schatzkammer” wines. “The wines need to breathe some under cork,” he says. Just his entry-level off-dry Butterfly Riesling is bottled under screw cap, not his Saarburger Rausch Kabinett, much less his Auslese wines.

The 1971 Wine Law, with its Prädikat system, has led some producers to believe that wines below Spätlese don't need a natural cork, as they should be consumed young. But many of these wines (often dry, with or without a Prädikat) can age longer than some of the higher Prädikats. It should be noted, too, that many of these Kabinetts and non-Prädikat entry-level wines have increased ripeness levels from improved vineyard practices and, of course, climate change.

A Question of Price

Winemaker Gernot Kollmann of Immich-Batterieberg says that there's a marked difference in price between a high-quality natural cork and a screw cap. A few years ago, he had the difference, in euros, at about 35 cents, but this can go higher depending on the quality of the cork, such as a longer 48-mm cork.

Oliver Fischer—who once sold natural corks for Korkindustrie Trier, a company that processes and sells corks to Joh. Jos. Prüm and many others—says a decent cork can be had for smaller sums. He gives a price of 35 cents for a quality cork and 25 cents for a screw cap. Klaus-Dieter Brech, an experienced sales rep for the cork company Rudolf Ohlinger, says it's about 30 cents for a quality cork and 12 for a screw cap. In other words, the price difference between cork and screw cap is anywhere from over one euro to 10 cents. This is an important cost, which, when multiplied, adds appreciably more to the price of an entry-level wine—even if starting at only a 10-cent difference.

Gernot favors natural corks but chose to bottle his basic Riesling, called C.A.I. (named after the former owner Carl August Immich), under screw cap to reduce production costs. Otherwise, he says, he would be unable to meet the price needed in the market for an entry-level Riesling, which, at around 4 euros net for the trade, is already an extremely tight margin in this competitive price segment. On the steep slate slopes of the Mosel region, production costs tend to be much higher than in the Rheingau, Rheinhessen, Pfalz, and most other German wine regions.

Carbon Dioxide

After some testing, Gernot also chose a screw-cap liner that works best for his style of winemaking. Yet he still feels that the same wine under natural cork tastes better and even experimented by bottling a small batch of his 2009 C.A.I. with cork to offer certain merchants and restaurateurs and to compare the two closures side by side over several years.

Besides sulfide reduction, Gernot's main concern with screw caps "is the very disharmonious integration of the carbon dioxide (CO2) in the wine." A problem that he says worsens with cellaring, as the "fat" CO2 stands out over the rest of the wine and develops unfavorable tannins. "One can practically taste the screw-cap closure (even wines bottled by 'experienced' screw-cap professionals) on nearly every wine," Gernot says. In order to reduce this problem, one has to change the way the wine is made to fit the closure, which is easier to do with a red wine that has aged for over 18 months in wood with little CO2, disregarding the eventual tannin problem. For example, Henrik Möbitz initially favored screw caps, even for his excellent Spätburgunders from near Freiburg, in Baden, but then decided to use natural corks for his reds. He feels the wines show better now.

In Germany, most producers work with a contract bottler and many of them have small doses of CO2 added at bottling to increase the freshness and aromatics of their wines. One device is called Carbofresh. This, however, tastes different from a natural, fermentative CO2. My research into the history of winemaking in Germany has revealed that adding CO2, like a selectively cultured yeast, was already practiced toward the end of the 19th century.

Gernot says screw caps showed less good to problematic based on well-organized blind tastings of the same wine bottled with different closures, including glass stoppers, which fared worse than the others. He realizes, however, that screw cap is deemed positive by many consumers, especially for young, fresh wines. And besides, only 5 percent of the clients actually cellar their wines. But he would never choose to use screw cap for wines that are meant for long keeping.

Daniel Vollenweider once bottled, on request, a batch of his fruity Wolfer Goldgrube Kabinett wines under screw cap, but he noticed that with age the same wine with natural cork tasted better. Christoph Schaefer of Willi Schaefer says that screw caps give his Kabinett wines a little more prickle and freshness, but he still likes to bottle a percentage with corks. Christoph's US importer, Terry Theise, insists on having screw caps.

Natural Cork Fans

In Wiltingen, in the Saar Valley, Roman Niewodniczanski of Van Volxem only uses natural corks for his wines, whether high-volume Schiefer Riesling and Saar Riesling or more expensive single-vineyard wines from the VDP-designated Grosse Lagen, or "great sites." His pricey corks come from Bouchons Trescases, a traditional French cork manufacturer, now owned by Amorim Cork.

For those who are wondering, corks are extracted from oak trees mainly in the coastal regions of Spain and Portugal and cause no harm to the trees, which support a unique ecosystem. On each finished cork, there is usually a mark or letter that indicates the manufacturer. Trescases has a distinct symbol and even brands the name and vintage of the producer on the cork. Most cork producers print instead with ink. Nevertheless, an expensive cork can have TCA taint as well. I recently had a corked bottle of Leitz's 2012 Berg Kaisersteinfels. The cork was from Trescases.

A.J. Adam, in Dhron, is another top-quality producer who refuses to use alternative closures for any of his wines. He prefers natural cork.* To my surprise (hence the strikethrough), Andreas Adam has decided to bottle his 2013 Gutsriesling and Dhroner Riesling with a screw cap. This saves on resources (for natural corks), he claims, and these two wines are usually consumed early. He says that the German gastronomical scene prefers Stelvin now and that there is an unpleasant "price war" going on, with more and more young growers in Rheinhessen and Pfalz who make good wines and bottle with screw caps at lower prices than Mosel growers. Andreas, however, doesn't want to bottle his Kabinett or higher Prädikat wines with screw cap. The same goes for his best dry and off-dry Rieslings. As he prefers spontaneous fermentation by ambient yeasts, he wants to avoid any extra stink from reduction and he feels screw caps are not ideal after three years.

On the other hand, Andreas's friend Julian Haart bottles all of his Piesporters and Ohligsbergers with cork, as well as his basic Mosel Riesling with a less expensive cork. Other big names who are fans of cork are Markus Molitor and Clemens Busch.

Many of the old guard keeps to natural corks, too. The list includes the esteemed estates of Egon Müller and J.J. Prüm, neither of whom use screw caps, even for their basic wines. (See comment.) The Prüms purchase their corks from Korkindustrie Trier; Egon Müller procures his corks from Rich Xiberta in Spain.

In Eitelsbach, Christian Vogt of the Karthäuserhof briefly experimented with screw caps for the 2011 Weissburgunder and Ruwer Riesling, but lost 15 percent to leaks and has decided to return to corks for Riesling in the foreseeable future. Other well-known producers have also reported troubling screw-cap leaks.

Other Alternatives to Natural Cork

For Weingut Stein's Blauschiefer Riesling feinherb, winegrower Ulli Stein uses synthetic cork made of plastic compounds. Ulli says that the key is the manufacturer, and the wines can last several years under this artificial closure if done right. He buys his plastic corks from Syncor, which give no taste to the wine. (In the US, vom Boden offers an exclusive selection of Blauschiefer Riesling trocken, rather than the off-dry Blauschiefer for the German market.)

Ulli has of late gone to an Italian-made screw cap for his liter bottling. The artificial corks are for Blauschiefer, rosé, and a sweet Riesling. Otherwise, he prefers natural corks for his best wines, even though he has been frustrated by cork taint at times, though not enough to switch over completely to alternative closures. He says that screw cap is fine for his liter Landwein. Besides, German restaurants prefer Stelvin. It's drunk up pretty quickly anyway. His private clients, however, prefer plastic corks rather than screw caps for the mid-range wines. "It's psychological," Ulli says. They want to hear that "plop" sound from an uncorked bottle. At Noma, in Copenhagen, the wine buyer wants natural cork for his Stein-Wein.

Ulli says that a lot can go wrong with bottling screw caps, unlike plastic corks. Stein's St. Aldegunder Himmelreich Kabinett trocken and feinherb, as well as the higher Prädikats, are all with natural cork. He buys only the top categories (Super, Extra) from Amorim. He feels that subtly corked bottles have gone down in recent years, and he doesn't look at the price for deciding on closures. Perhaps, if the quality continues to improve, he'll go back to natural cork for all his wines, except the liter, which will remain under screw cap.

The main problem with plastic corks is oxidation, plus the bottles are difficult to open, often ruining good corkscrews. Plastic corks also do not reseal and are not biodegradable. On the plus side, producers do not need other bottle types or a different bottling line for synthetic corks. An additional concern is how most plastics, such as those used for water bottles, leach chemicals that act like the sex hormone estrogen. This is cited in a study that was conducted by a team of researchers, including Dr. George Bittner, Professor of Neurobiology on the University of Texas at Austin. They tested plastic corks from Normacorc.

Another alternative to natural cork is the more expensive glass stopper, which has an O-ring silicon seal that goes around the lip of the bottle. There are, however, question marks about the seal's integrity over time, as well as CO2 escaping at bottling. One brand is Vinolok, which comes in both a low- and high-top version and in various colors. On the Mosel, Martin Kerpen and Reuscher-Haart use Vinolok. In the Rheingau, Schloss Vollrads, Schloss Reinhartshausen, and J.B. Becker are all Vinolok clients. J.B. Becker is an old-school Rheingau producer who switched to Vinolok several years ago. Personally, I don't think it was a good choice for Becker. His old-style Rheingau Rieslings, which age in the traditional 1,200-liter Stück casks and can last a long time in bottle, would seem better suited to corks, as glass closures don't fit his winemaking regimen and don't have a track record of long aging.

The Saar grower Manfred Loch of Weinhof Herrenberg lost all of his production in the 2003 vintage because of TCA, despite choosing the best corks on the market. Unfortunately, the cork manufacturer that starts with the letter "T," gave him zero compensation. He says that his production was too small to be a concern for them, even though he could have gone bankrupt if it happened again. Many producers buy from various cork manufacturers to avoid such a loss. After this horrible experience, Manfred decided that enough was enough. In 2004, Manfred switched to a crown cap, though the glass works have stopped manufacturing enough wine bottles specifically made for this closure. He now uses GlasTwister, made by Syncor, an odd-looking stopper that is more sturdy and elastic than a screw cap. "It takes getting used to," Loch says. Unlike crown caps, GlasTwister doesn't need a bottle opener and can be easily resealed. Manfred likes that and wouldn't want to go back to crown cap either.

So why not screw caps? "Screw caps are sensitive, especially for small- and medium-sized producers who don't have the means to pack all their wines right away into cardboard cases," Manfred says. Instead, the screw-capped bottles are usually put in iron-barred boxes for storage. When laying down the bottles into these boxes or even while in transit, the caps can be punctured and begin to leak. In order to avoid this, producers are now using plastic stackable layers that hold individual bottles and protect against this.

Screw caps require a special glass bottle finish, or thread, known as BVS (Bague Vin Suisse) and these, like the screw caps, are intricate and have to be perfect, plus it takes a lot of know-how to properly bottle wines under screw cap. "Many producers and even contract bottlers lack the necessary expertise," Manfred says. The upper lip of a screw-cap bottle often has a rough edge that can also cause leakage.

The Rise of Screw Caps

Eva Fricke, who worked both at J.B. Becker and Leitz before starting her own winery with vineyards in Lorch and Kiedrich (on opposite ends of the Rheingau), uses screw cap for her entry-level wines and natural cork for her top single-vineyard wines. She says that German clients expect screw caps for basic wines now and she actually likes the extra freshness screw caps can give her Rheingaus.

Klaus-Dieter Brech says that 70 to 80 percent of German wines are topped with screw caps now. The movement to screw cap, he says, began in 2002 or so. He attributes the high demand for natural corks in the late 1990s to overproduction and poor quality. The cork industry was to blame for a lack of quality control. In Germany, there was a strong backlash against natural corks, for which screw caps were the best alternative, especially for early drinking wines.

This had much to do with the storing of the oak bark, where it easily could pick up TCA. Because of the high incidence of corked wines, many German producers and clients developed a strong dislike of natural corks.

Today, most German wine regions have a higher percentage of wines bottled under screw cap than on the Mosel. Oliver says that many of the regional co-ops, like those in Baden, as well as many producers in Franconia, went to screw caps early on. The latter had a lot of issues with cork taint. Some of this, he says, was due to the bulbous Bocksbeutel bottle, which has a short bottleneck that requires the cheaper 38-mm cork. These were often the worst quality, hence producers sought alternative closures and ended up switching to screw caps. (The Bocksbeutel is a traditional bottle shape in Franconia and certain parts of Baden.)

Oliver points out that TCA isn't limited to wine. "Different produce can be affected by this taint, like coffee and pepper," he says. "Even the organic zucchini that I recently bought smelled of TCA."

In the Nahe region, Matthias Adams of Weingut von Racknitz decided on screw caps for all his wines, which, like Heymann-Löwenstein, are bottled later than most producers. Matthias made this choice based on his belief that screw cap is better than natural cork. He doesn't want to have to deal with TCA and, when asked about aging under Stelvin, he likes to point out that Penfolds has a long track record of using a screw cap.

A Detractor of Screw Caps

Wine critic John Gilman, author of the bi-monthly newsletter View From a Cellar, has been an outspoken opponent of screw caps. He doesn't like that some of his favorite producers, such as Maximin Grünhaus and Willi Schaefer, have begun to bottle more of their wines, including a portion of their fruity Kabinetts, under screw caps. In an interview for Tyler Colman's Dr. Vino's wine blog, Gilman airs his views on screw caps:

In my opinion, the closure is fatally flawed as it is used today, and I find it inexcusable for so many winemakers and winery owners to try and sweep the flaws under the rug instead of fessing up that they were screwed by the early propaganda and half-assed research—that the screwcap technology is still not ready to gracefully age wines—and switch back completely to corks until a time when the alternatives are really ready. Instead, we have all this “copper fining” BS—adding heavy metals to the wines so that they can use a flawed closure system is in my opinion just asinine and ethically bankrupt—and every other sort of winemaking manipulation ever conceived by man to try and get the wines ready to seal up under screwcap. Of course the jury is still out on whether or not adding huge doses of copper sulphate to the wines pre-bottling is safe for those consuming the wines, but I for one am not about to be the guinea pig on that score.

Gilman goes on to say that beyond such "treatments," the wines "go into permanent reduction under screwcap and are ruined. How do you make a screwcapped wine taste and smell like rotting cabbage or burning rubber—put it in the cellar for a few years[?]" He's talking about sulfide reduction and explains this in more detail, as well as other screw-cap gripes, in a well-written reply to a Decanter article that is discussed on the Bacchus for You blog (which, unfortunately, is awfully difficult to read because of the black background).

Reduction

Some producers have reduced notes in their wines, and screw cap can accentuate this stink even more. For example, I notice, on occasion, a marked reductive stink on the wines from VOLS and Maximin Grünhaus, less so from Später-Veit and Selbach-Oster. (See "What's the Stink?”)

Jamie Goode explains that screw caps offer a tighter seal than natural or synthetic corks, thus they encourage more reduction, which is often described as rubbery. This aroma comes from "chemical reactions of sulphur compounds in a reduced environment" of a screw cap and can be eliminated by taking certain measures at bottling, such as "bigger head-space" and less sulfur. Goode says that long-term aging of screw caps is still questionable. On his wine blog, he says:

Cork is a wonderful natural product, which does a great job sealing wine bottles. It's only as we've moved away from cork to alternatives that we've found that the technical requirements of a wine bottle closure are not all that simple. What cork does (and this seems to be important), is to allow a slow release of oxygen from its compressed cellular structure for the first few months after bottling, and then a very low level of oxygen transmission from then on, through the cork/glass interface. The level of gas transmission by a sound cork seems to be just enough for optimum wine development, but not too much (in reality, it's hardly any at all).

"Mosel Riesling is quite sensitive to cork and other phenol substances," Oliver says. At the same time, it is also sensitive to Böckser (sulfide off-flavors), especially from early bottling under a screw cap. The oxygen management and transmission rate are too often overlooked. Not only does the grower need to time the bottling for screw-cap closures, the mouth of the bottle, or thread, and the screw cap needs to be flawless.

In addition, wine author Joachim Krieger says that Mosel Rieslings bottled under screw cap tend to fall apart quicker after opening, especially if the wine is consumed over several days. It seems to him that the wine is then less suited for contact with oxygen.

An Influential Screw-Cap Backer

The American importer Terry Theise is a fan of screw caps. It's understandable. He has fewer worries of clients coming back to him, or Michael Skurnik Wines, with complaints about cork taint and asking for their money back. This can be stressful and might be easier to avoid. In his Austria 2013 catalog, he writes, "I'm happy to report cork is almost a non-issue these days in Austria, as the majority of people with whom I work have moved over to screwcaps with a celerity that should give their German brethren a kick in the pants. Everyone spoke of adjusting SO2 levels and otherwise monitoring the wines for any signs of distortion in the new regime. But it was such a relief to stop worrying." In Europe, the Swiss have actually been at the forefront of using screw caps since the 1980s.

One of Theise's favorite producers is Dönnhoff, which now bottles their basic Riesling and a fruity Kabinett under screw cap. Helmut Dönnhoff had been reluctant to do so in the past. He much preferred to bottle his Nahe Rieslings under natural cork.

On the Internet forum Wine Berserkers, Terry Theise replies to a reader about screw caps and even mentions Dönnhoff:

I see them as the lesser of two evils. Among the many growers with whom I work, those who've made the switch have managed it easily by diddling the SO2 levels at bottling. It's not my experience that the wines "go nowhere." I rather think we've begun to suppose that the accelerated development under cork is somehow normal.

The Austrians have been quicker off the mark than the more staid conservative Germans. Dönnhoff is entitled to his view, of course, just as I'm entitled to question it when I pour another corked bottle of his wine down the drain. In his case there's a larger question in play, inasmuch as I'm willing to concede that the particular (and precious) texture of his wines are aligned with the gentle oxygenation that cork provides.

As for Dönnhoff, it would be good to compare over several years the same wines bottled under a cork and screw cap.

Conclusion

As Goode points out, healthy cork is a natural material ideal for sealing bottles, and it has a long tradition. Wines bottled with cork tend to be more in harmony and less reduced than those bottled under screw cap. In contrast, the production of aluminum screw caps is less environmentally friendly than corks. It's doubtful, as well, that most of the screw caps end up being recycled. Corks, on the other hand, are biodegradable.

The incidence of TCA for corks is said to be less than 3 percent, down from as high as 5 to 10 percent. Oliver says that corks have improved in the last 10 to 15 years. The corks have more thorough quality control measures. The trees are selected more carefully. He also says that the cork-resting process has improved and the washing process is better than before.

"The danger is when some find that screw caps are the cure for all problems," Oliver says. And this is based on false perceptions. He adds, too, that the discussion, on both sides, is extremist, much like religion. Moreover, lobbyists play a role in forming wrong opinions. At the same time, he doesn't understand how producers can take such "perverse" measures to bottle their wines under screw cap, such as fining with copper or using micro-oxygenation, which both strip the wines of their character. In other words, a producer should be fitting the closure to their style of wine and not vice versa. "They don't always consider reduction, aging, and sulfur," he says. "If a grower prefers a reductive, spontaneous fermentation, then screw caps might be a poor choice."

The battle between natural cork and screw cap reminds me a little of natural grass versus artificial turf in football, with the manufacturer Stelvin as FieldTurf. Stelvin might be more reliable but it is artificial and has its own flaws. Traditionalists prefer natural cork closures, and you can count me among them for most Mosel wines, even though I've experienced the frustration of opening many corked bottles. ♦

*Beginning with the 2013 vintage, Andreas Adam felt it was necessary to switch to screw cap for his entry-level wine, largely because of demand from restaurants and the wine trade in Germany.

  • Uwe Kristen says:

    Thanks for this detailed article on closures. I very rarely have to pour a corked bottle down the drain. I guess I don’t drink enough wine or just have a high threshold for TCA. I like cork because it is a natural product. As you point out, cork tree forests support a unique ecosystem and their product is biodegradable. Screw caps on the other hand need to be manufactured. It costs energy to make them and the production is everything but clean. Screw caps aren’t recyclable either (at least not in the U.S.). As a wine drinker I cherish the idea of a sense of place. In order to guarantee that for the future I feel we need to worry not only about long-term aging but also about the environment. Screw caps don’t seem to be the answer.

    • You’re welcome. In 2009, I remember writing you about my wish to have Henrik Möbitz discontinue using screw caps for his Spätburgunder wines, because the bottle development under screw cap seemed to make the wines taste hard. Back then, you favored screw caps.

      You raise an excellent point about the energy costs and the environmental impact of screw-cap production. I talked with Carl von Schubert about this as well. He says that in Mertesdorf, nearby his Grünhaus estate, there is a state-of-the-art recycling center (which, I’ve heard, is not in use). Yet I doubt that most of the screw caps get recycled even in Germany. After the latest Intergovernmental Panel on Climate Change (IPCC) report, we should be thinking more about global warming, too.

      • Uwe Kristen says:

        I admire your memory! It is true that I welcomed the screw cap on Henrik Möbitz’ wines back then. Every time I traveled to Germany for a visit I brought back a few bottles of his wines and always was worried that one of my treasures could be corked. Little did I worry about the negative impact of screw caps on Henrik’s wines. Luckily, you (and Henrik) worried about that.

        Even if I don’t experience corked bottles all that often I thought why not erasing the risk altogether by using screw caps. Until I saw Patrick Spencer’s presentation “From bark to bottle”: https://www.youtube.com/watch?v=YDE7OXr-5gg#t=110. Now I think that as someone who likes his wine to be as natural as possible I need to take into consideration that screw caps and plastic corks are piling up on landfills. If we don’t think long-term in regard to the environment we soon may end up not having anything worth in the bottle to age for long-term either.

  • Sasha Katsman says:

    Lars, thank you for an informative and balanced article on closures.
    I am particularly intrigued by the fact that, even within Germany, I have less of an issue with wines under screw cap from some regions than from others. An extreme example would be a failed recent attempt to tell two bottles of the same young Swabian Riesling, one under cork and the other under screw cap, apart. Sadly, it is the region that your website is dedicated to that has caused me to express the most closure-related grievances. And yet, even within the Mosel, my reaction varies. I was going through a particularly rough patch with a bunch of my favourite 2009s from the Mosel misbehaving (or should I say behaving in ways unfamiliar to me?) under screw cap, when I found myself at a portfolio presentation conducted by Dan Melia in Boston. It is most unfortunate that I did not end up taking notes that day, but I recall being shocked at how well some of the wines, particularly from the 2010 vintage, showed under screw cap. At the risk of getting it wrong, Stein, Immich and Steinmetz come to mind as possible sources.
    Why such different reactions? A simple explanation may be that, as purely a consumer, I have the lame excuse to forgo the science and “vote” with my wallet. If I buy a Kabinett from Wehlen in every vintage, but the quantity I purchase ranges from three bottles to two cases depending on my early assessment of the wine, an unfamiliar pattern due to closure renders my judgement irrelevant due to lack of historical context. On the other hand, tasting a new producer, as Immich would have been to me with the 2009 vintage, I have no frame of reference and can therefore be more open minded. A much more complicated answer would be that there are differences between regions, whether due to bottling practices, typical chemical composition of the wines or even of the soil. And if such differences exist, why couldn’t a wine’s behavior under screw cap vary from year to year? Could a very unusual composition of the 2010s in the Mosel have obliterated anything we can discern when comparing closures? Will the 2013s do the same?
    One of the most interesting passages in the article is the quote from Gernot about “fat” CO2.
    Last month, I was involved in a blind tasting of two bottles of the same Riesling with a bit of age on it, perfectly sourced, one under cork and the other under screw cap. Apologies for withholding the details, but I had given my word not to publicize for the time being. This was probably the easiest blind tasting I’ve ever been involved in, but I made sure to finish all my remarks before the veils were lifted. The wine which turned out to be under screw cap looked years younger, but the other, while a deeper and darker golden-green, produced a certain shine, while playing with the light, that its sibling could not. On the palate is where real trouble began though. Under cork we had a more developed wine of immense reserve, depth and complexity. Under screw cap, we had, relatively speaking a more primary half-wine, one that came up short in every department – half the complexity, have the depth, half the concentration, remarkably all in an extremely youthful fashion. This would be nothing were it not for a most telling characteristic in evaluating a wine at difficult stages of evolution – you guessed it, the second wine had half the length. An overall anecdotal impression of the second wine was of one whose components did not develop uniformly. I joked, after the fact, that a certain type of corked wine – one that displays no TCA aromas, but displays all the damage on the palate – would have behaved this way.
    While I would not jump to conclusions based on a single experiment, the reason I found Gernot’s quote so interesting is because the wine under screw cap above had retained considerably more CO2. Is Gernot’s implication that the effect is permanent? I would have a difficult time correlating this particular experience with what he calls “unfavorable tannins”, but being mostly in uncharted waters here, I have to consider all possibilities.

    • Wow! Thanks for your long reply, Sasha. Stein and Günther Steinmetz only began to use screw caps for entry-level Rieslings, bottled in liter and post-Mosel Wine Merchant. Ulli Stein first started to use screw cap for his liter bottling last year. In our former portfolio, Weiser-Künstler, Immich-Batterieberg, Knebel, and Peter Lauer already had screw caps for their basic Rieslings. So much depends on the producer.

      As I understand, Gernot feels that the “fat” CO2 doesn’t really integrate.

  • Randall Grahm says:

    While I am an enormous fan of the work that Lars is doing in exploring the magical world of Riesling, I feel that the general thesis of this article was off-base, and the consideration of the positive and negative aspects of screwcaps for Mosel wines was utterly skewed in the wrong direction. The so-called “problems” of screwcaps in my opinion are just phantasms, they don’t really exist. Further, what I believe is the greatest benefit of the screwcap for Mosel wines, i.e., its relative impermeability to oxygen, is not really addressed, but I will rectify that forthwith. First, the primary alleged flaw of screwcaps, i.e. the issue of post-bottling “reduction,” or more properly, the expression of certain reductive species, to wit mercaptans or thiols, is seldom if ever an issue with white wines. White wines do not possess the reductive capacity of reds, i.e. they lack tannins and anthocyanins, which are the primary antioxidants found in wine. I have never in my experience ever bottled a white wine that was clean going into the bottle that subsequently developed reductive aromas. The greatest advantage of screwcaps, apart from avoiding the issue of cork taint and mechanical failure of corks (which are still both non-trivial issues – Riesling in general and Mosel wine in particular because of its nature, is particular sensitive to the transmission of cork taint), is the fact that it so efficiently excludes SO2. This affords the winemaker unique stylistic opportunities. If a winemaker, for example, is intending his wine for earlier consumption, he can potentially bottle his screwcap wines with lower levels of SO2 than the same wine sealed with cork, thus, arguably produced a more interesting wine (with less bitterness and harshness). On the other hand, if it is a great Spätlese or Auslese and is intended for long-term ageing, he is likewise able to achieve much greater longevity in the bottle with a screwcap as compared to a cork. The SO2 will take far longer to get bound up, thus extending the life-span of the wine. Screwcaps are generally believed to have a useful life of at least 30 years (longer than a cork, by the way), which is generally considered within the realm of when most wines are likely to be consumed. If there has been a problem with the acceptance of Rieslings in general, the single biggest issue for me is the often very high levels of free SO2, or more accurately, the levels of molecular SO2 found in young wine (in virtue of the extremely low pH of Mosel wine in particular). Many customers have SO2 sensitivity, and many just simply don’t want to experience the harshness and pungency of wines that are “pickled.” Screwcaps in this way, allows the winemaker the opportunity to present his or her young wine to a wider audience in a far more congenial format with lower levels of free SO2. The business about “fat bubbles” in wines bottled with screwcaps?: I’ve never read such a non-issue in my life. (That is really grasping for straws.) If one rejects screwcaps because they are not “traditional” or “classical” I think that is barking (as it were) up the wrong tree. As Riesling lovers, we have never worried about what other people have thought about what we drink; why should we begin now? I think that the only real argument in favor of corks is potentially the fact that they are at least theoretically a renewable resource, though it is not at all obvious to me whether screwcaps or corks have the lesser carbon footprint. (Screwcaps are at least theoretically recyclable, though screwcap manufacturers need to do a better job in helping to promote that outcome.) But, for me, as a winemaker, the integrity of the wine is what matters the most; how can I bring my bottle to market to show the maximum respect for the grapes and vineyard that produced it? For me, especially with Mosel wine, the answer is irrefutably to bottle the wine in screwcaps (for all quality levels.)

    • Randall, I really appreciate your taking the time to reply to my article. My piece lacks a thread, but I wanted to bring up different issues and points of view. A number of Mosel producers, like Karthäuserhof, have had serious problems with screw-cap leaks. In addition, I do find that some Mosel wines that are bottled under screw cap taste overly reductive, especially when compared with the same wine under natural cork. The cost factor for entry-level Mosel wines also plays an important role for many producers. It would be best for a Mosel winemaker to comment about SO2. At Hofgut Falkenstein, Erich Weber uses relatively low levels of SO2 and bottles all of his Saar Rieslings with natural cork.

    • Andrew Bair says:

      Randall –

      I’m glad to see you here, and found your counterpoint to Lars’ article very interesting. The screwcaps (And glass stoppers?) vs. corks debate is one that I am very much on the fence on – an umblemished cork may be ideal, but then there is the risk of being disappointed when you cellar a bottle for 20 years, only to find that it is corked. Perhaps my low incidence/sensitivity to TCA has led me to give corks the benefit of the doubt for now.

      Also, I was very impressed by your wines at the Boston Wine Expo back in February. The Cigare Blancs were a revelation to me as someone who rarely gets excited over Rhône Ranger whites, yet enjoys a good Saint-Joseph or CDP Blanc.

    • David Schildknecht reminded me of Jamie Goode’s article on mercaptans and other volatile sulfur compounds. As David says, “Jamie devotes most of the piece to white wine” and the problems with screw caps.

    • Sasha Katsman says:

      I disagree that the article Lars posted is skewed, given the main purpose it is meant to serve, which is to explore the screw cap. As such, the article is, and should be, mostly dedicated to that closure. This has nothing to do with personal preference for either closure. In fact, if screw cap is the superior closure and represents the future for most bottlings, it is that much more important to continue challenging it at this juncture. This is, if you will, a scientific responsibility.
      If, as you say, the life cycle of a screw cap is about 30 years, then I will continue exploring and challenging this closure until I am convinced that bottles of German Riesling which are important to me complete a satisfactory journey during that time frame. Until then, the benefits of any closure without sufficient track record remain theoretical.
      What is clear to me is that not all wines under screw cap are created equal, a fact I have alluded to in my post above. Why some regions do better than others, and why there is so much less taste difference when the same wine is bottled under difference closures in some regions/for some varieties than others is something that I do not yet understand, nor has anyone been able to explain to me successfully. Thus, evidence of a different variety in another country having done well under screw cap is about as relevant to me where Mosel Riesling is concerned as the success of Russian vodka under that very closure.
      Mosel wines I have followed react strongly to closures, for better or for worse. Once again, if the screw cap is the way of the future for these wines, it would be more productive to understand the reasons behind these differences rather than to dismiss them as “phantasms”.

  • Andrew Bair says:

    Lars –

    Thank you for the article. Like Uwe, I seem to have a lower than normal incidence of corked bottles – as he says, perhaps both of us have low sensitivity to TCA. (That said, I’ve also had quite a few bottles with corks that didn’t have the classic “corked” aromas, but seemed to be noticeably off. Whether those had anything to do with the closure is pure speculation.)

    Domaine des Baumard – one of the leading Loire estates in the mind of everyone except for Jim Budd – went all in with screw caps several years ago. I will be very interested to read how their Savennieres and their top sweet wines (Clos St. Catherine, Quarts du Chaume) develop under screwcap. In the past, the Baumard wines aged very nicely – I enjoyed a 1971 Clos St. Catherine in 2008, and their “regular” 1990 Savennieres in 2007.

    Similarly, I would be interested in reading a retrospective tasting of wines bottled with glass stoppers, which seem to be most prevalent in Germany.

    • You’re welcome, Andrew. J.B. Becker in the Rheingau has been using glass stoppers for several vintages now. It’ll be interesting to taste some of these wines down the road. As I wrote in my article, I don’t think it was a wise decision for his style of wines, which are otherwise made in a time-honored manner.

  • I stand corrected. Neville Yates of Eurocentric Wine in Australia finally sent me a photo of a screw-capped 2012 Scharzofberger from Egon Müller.

  • Neville Yates says:

    Yes, I believe all Egon Muller wines sold in Australia are sealed with screwcap. I’ve certainly got spatlese, auslese and auslese goldcap under Stelvin. One of the most infuriating things for me as an importer is that there are so many weak corks used by German producers. We get more leakers than cork taint, and I used refrigerated trucking, shipping and storage, so it’s not from exposure to heat. I bought six magnums of 2010 kabinett from Maximin Grunhaus and three of them are leaking already. Screwcaps are well accepted by most in Australia and it’s quite rare for local white wines to be sealed with anything but screwcap. Having tried some of those early 1970s wines sealed this way and being wowed by the purity and consistent development, I am confident they are the way to go. However, there does seem to be more reduction in some drier German wines in the first couple of years under screwcap. It’s not a problem though. Give the bottle a shake or vigorous decant, wait 30 minutes and jump in.

  • As it turns out, Egon Müller does bottle his various wines under screw cap. His merchants or importers decide on which closure they prefer. If they choose screw cap, then it has to be for all the wines, including the higher predicates.

    Müller is most concerned about the incidence of corky wines, because the corkiness is often slight. He says that even some experienced sommeliers don’t notice that a wine is corked. At the same time, he admits that the really musty corks are less prevalent than they were in the past.

  • In translating Ulli Stein’s latest newsletter, he talks about different closures and says that the new generation of plastic corks are made from renewable and sustainable polymers based on sugar cane and are carbon neutral. The oxygen exchange can also be regulated. In addition, these plastic corks are neutral to the taste and can protect the wines from oxidation and aging up to eight years in the bottle. Ulli uses these for his Blauschiefer, rosé, and mid-range wines. His liter is bottled under screw cap. For his top wines, including Kabinett, his preference is natural cork.

  • Al Drinkle says:

    Despite this recent inactivity of this thread, I feel compelled to comment based on a recent experience regarding what I perceived to be reoccurring TDN in several examples of wines with Stelvin closures.

    To clarify, TDN (1,1,6-trimethyl-1,2-dihydronaphthalene) is a chemical compound that has been found in Riesling wines in up to six times higher quantities than in other mainstream grape varieties. TDN and its precursors have been linked to the “kerosene,” “gasoline,” etc. aromas that many tasters assert is present in some wines and Riesling in particular.

    There is a good reason that I’m commenting now, and not a year and a half ago when I first read Lars’ excellent article. In September, my wife and I began a vacation with a brief stint in the Rheingau and delighted at the fact that I had a rental car and several days of freedom without a heavy tasting schedule (and therefore time for leisurely sipping), both Johannes Leitz and Andi Spreitzer generously bid us farewell by packing our car with intimidating quantities of wine, made both by themselves as well as colleagues. We dedicatedly eliminated countless bottles over our regrettably short time in the Mosel (where a stop was made at Rieslinghaus/Weinhaus Porn in Bernkastel – more bottles!) and beyond before boarding a plane on which I wanted to be liquid-free.

    I made an interesting observation and here is an excerpt from a note that I wrote from Leiwen in the Mosel to friends and colleagues in Calgary, Canada:

    “… Lastly, a point that I anticipate discussing in more detail in person – I’ve been working my way through the formidable pile of wines that I’ve accumulated (ending the trip in Greece without a car negates the option of hauling cases around for much longer). Many are 7-15 years of age and about half, notably a range that Leitz bottled specifically for Marks and Spencer in the UK, have Stelvin closures. From this random sampling, I’ve noticed that every single wine, German and Austrian alike, with five or more years of bottle-age and sealed with a screwcap shows some degree of TDN (some subtly and appealingly like the ’07 Leitz Roseneck Spätlese, and some horrifically like the ’09 Bernhard Ott Rhein Riesling from Wagram). Most surprising is the kerosene-dominated 2009 Leitz Roseneck Trocken “Marks & Spencer,” especially considering that I’ve had so much clean and pure aged wine from him, like the cork-sealed ’06 Roseneck Spätlese or ’98 Rottland Auslese Trocken from a few days ago. It’s not only Riesling either as the screwcapped ’03 Hirsch Lamm Grüner is a diesel-bomb too. On the other hand, the countless cork-finished Rieslings that I’ve been enjoying have either been completely free of TDN, or show the faintest, integrated whisper… Although one irreplaceable bottle was egregiously corked!”

    I’m not authoritatively stating that a screwcap and age is a sure sign of TDN-domination, but I found my particular lineup of bottles, tasted over an unusually short period of time, to provide me with an uncanny pattern that must go at least somewhat beyond the realm of coincidence. Please also note that I don’t write off bottles based on the slightest presence of TDN, but like anything else in wine, as soon as it’s out of balance (which must be a personal opinion, I suppose) it’s unacceptable.

    Upon returning home, I uncovered an article by the Australian Wine Research Institute wherein extensive research into the causes of TDN and ways in which it is perpetuated in the bottle corroborate my empirical findings in one important way. The group of researchers report that cork closures have a way of absorbing (do they mean releasing?) up to 50% of the TDN present in a wine over a period of two years whereas screwcap closures do not allow TDN to “escape” at all. Unfortunately the mention of closures is made in passing and there is very little detail beyond what I have just paraphrased.

    Lastly, I recall reading in one of Terry Theise’s catalogs at some point that his opinion of the “gasoline” aroma is that it is indicative of a wine’s adolescence, not ultimate development, and that it is a phase that Riesling might simply pass through on the road to true maturity. Again, I am paraphrasing here and I hope that I’m getting this right, but does this reflect anybody else’s experience?

    Can anybody with better insight into this issue elaborate?

  • David Schildknecht says:

    That’s quite a tale, Al – and almost surely an important one.

    I have to confess that I do not get a lot of opportunity to re-taste 5-10 year old screw-capped Rieslings. The growers from whom I personally tend to cellar bottles in very small numbers happen to bottle most or all of their wines with natural cork. And when I am tasting with the growers I tend to be so pressed for time that usually at most just one or two wines other than those of the vintage currently under review manage to get tasted, and those could be anywhere from 2-25 years old, so the number of these from which one could extrapolate judgements about how screw caps perform with Riesling over time are few. I have to make an effort to remedy this deficiency.

    That having been noted, I do happen to have tasted a number of Hirsch Rieslings at 5-10 years and found them delicious, and also a bit less evolved than I speculated that they might have been had they been sealed with natural corks.

    I have to make yet another confession though. Perhaps I am insufficiently sensitive to reduction issues. But I simply don’t detect difficulties with screw-capped Rieslings of the sort that some of my friends and fellow wine critics say vitiate them. On the other hand, neither do I lack for experience – just not routinely – of Rieslings whose degree of reduction I find disturbing and at the same time speculate has been engendered or exacerbated by screw cap. I have to add that when I read the partisan “literature” on this subject I am routinely confronted with claims that either run very much counter to my organoleptic experience, and/or claims whose consequences strike me as utterly counter-factual. And that being the case, I am more than a little suspicious that in explaining my inability to corroborate the “findings” of some other critics the fault does not lie SOLELY with my olfactors and memory, but rather that these critics are to some extent influenced in their organoleptic perceptions by their strong partisan feelings in favor (or rejection) of screw caps.

    I DO have quite a bit of experience in tasting side-by-side, within six months of bottling, “the same” wine under screw cap and under cork. I always perceive at least a slight difference and more often a significant one. HOWEVER, I cannot by any means always pick-out on an organoleptic basis which wine was closed with screw cap and which with natural cork. I’d say I get that right about two-thirds of the time. Moreover, I don’t have a really strong preference at that very youthful stage for the wines closed in one rather than the other way. I’d say I prefer natural cork-closed bottles around two-thirds of the time. I don’t want to take time for details regarding the factors I think are relevant (some, such as reduction, CO2 retention and sulfur dosage being obvious)but I thought I ought to lay out all of the above so that anybody who takes time to read what I have written will have a notion of “where I’m coming from.”

    NOW (at last!) to the core of your fascinating observation! I actually DO (though perhaps in error) consider myself very sensitive to TDN and related phenomena or compounds. (I added that “related” because I detect DISTINCT aromatics with a family resemblance to gasoline.) But I have not noted a correlation with screw capping. Well, let me clarify that remark. I HAVE noticed a correlation, but I have chalked it up to matters of terroir (in particular sunshine and warmth), viticulture (in particular aggressive foliage removal) and wine making (in particular arch-reductive methods), because the correlation has been between New World Rieslings – a significant majority of which happen to be screw-capped – and TDN.

    A couple of the Hirsch Rieslings I’ve tasted exhibited slightly fusil notes, but I attributed these to vintage characteristics. And I consider the presence of significant TDN a decided detriment.

    You might dimly recall from the early days of the AWRI campaign against natural cork that some of the “science” cited included references to aromatic compounds that a natural cork allegedly “scalps,” and it’s conceivable that “scapling” represents an appropriate description of something natural cork also does over time to TDN.

    I am aware of Terry’s opinion about fusil notes being associated with a particular stage in Riesling’s development. Unfortunately, I can’t – from my somewhat more limited experience – confirm that view. I’ve had quite old Rieslings that were decidedly fusil and in fact have long associated this with the long-term evolution of a significant share of Rieslings from Alsace. And I’ve definitely had 5-10 year old and on an oxidative scale quite mature Australian, Finger Lakes or Oregon Rieslings that were strongly fusil and subsequent vintages of which I already in their youth found deleteriously tinged with TDN.

    I DO really hope that somebody out there with some scientific expertise as well as of course other Riesling lovers with experience of the relevant phenomena will weigh-in.

  • Al Drinkle says:

    David, thank you for the very detailed answer.

    When you mentioned that you had noticed a correlation between screw cap closures and TDN but had aligned it with the provenance of the wine and therefore catalysts, not exacerbators, of the phenomena (I know, I’m incompetently paraphrasing AND making up words!) it reminded me that I had previously felt the same way. To your list of Australian, Finger Lakes and Oregon Riesling, and despite my limited experience with the last two, I would add countless Canadian Rieslings and some from New Zealand as enthusiastic hosts to TDN in many cases. Based on reading and tasting, I had considered growing conditions (high temperatures, hydric stress, nitrogen deficiency?, etc.) and viticultural decisions (primarily leaf-thinning and therefore excessive sun exposure), but never had I considered closures.

    I suppose that subconsciously I was of the opinion that LOTS of Australian Rieslings had detectable levels of TDN whereas most Mosel Rieslings of comparable ages did not, and bottles from other places of origin lay somewhere in between. The idea of screwcaps having anything to do with TDN is brand new to me and hasn’t superseded the importance of the aforementioned factors, but it’s certainly something that I’ll continue to consider.

  • David Schildknecht says:

    Thanks for replying, and hopefully some folks out there can help us with chemical speculations on this apparent correlation of TDN and screw-capping (or for that matter on issues of TDN and bottle age generally).

    (I had considered adding New Zealand and Ontario to my list but have tasted fewer recent Rieslings from those places.)

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