Corks and Closures Natural Corks: The stereotypical "cork" produced by drilling a cylinder out of the bark of cork oak trees (Quercus suber). Technical Corks: Any of a number of engineered cork closures including colmated corks and agglomerated corks, but not including synthetic (non-cork) closures. Colmated Corks: Technical corks where any holes or voids that would ordinarily prevent a seal have been filled with a synthetic compound. Agglomerated Cork: Any technical cork formed by gluing small bits of cork together. The size of the cork bits used vary from manufacturer to manufacturer and from grade to grade. May include non-cork components other than the binder. May also be produced with either one or two cork disks on the ends. 1+1 Corks: Agglomerated corks with a disk of cork affixed to either end. 2+2 Corks: As per 1+1 corks, but with two cork disks attached to either end. Synthetic Closures: Any bottle-closure that is not made from tree bark. Includes both in-the-bottle closures, that function like corks, as well as cap-style closures like crown-caps and screw-caps. Screw Caps: Most broadly, any cap that is screwed on to corresponding threads on the bottle. In the wine industry, the screw caps in use include both short- and long-skirted designs. The term has several synonyms including both ROTE (Roll On Tamper Evident) and ROPP (Roll On Pilfer Proof).

I took a field trip recently. Actually, I journeyed across the entire country to take a look at an industry supplier's latest expansion. On one level, the story of my travels is merely a recent iteration in the ageless story of the quest for "the better mousetrap," a possible solution for an irritating problem plaguing the wine industry. One man with a good idea and the struggle to make an impression in the marketplace.

A Ruined Treasure

As most things should, it started with a bottle of wine. Not long ago, I opened a bottle that I had been passed from my father's cellar to my own. I had been hording it for several decades. Because of what I found when I opened that bottle, I won't divulge the winery or the brand, but suffice it to say that the producer was well respected, the vintage well regarded, and that more than a few writers had waxed eloquent over this bottle's siblings. After the "ploc" of extracting the cork, the gentle "glug" of the pour, and the first, much anticipated sniff, I was broadsided by the unmistakable reek of the industry's nemesis, tri-chloroanisole. "It's corked!" I cried.

Of course, this wasn't the first "corked" wine I've opened. Indeed, and unfortunately, as a wine judge I encounter TCA-contaminated wine all too often. As most readers will know, corks aren't the only means by which wine can become "tainted." Nevertheless, TCA remains associated with corks to the point at which the two are considered synonymous.

The desire to avoid "taint" has led to a number of changes within the closure industry. First, and perhaps most notably, the natural cork producers have changed their methods of production, changing from chlorine- to peroxide-solutions for bleaching to cite one example (see sidebar for the significance of this change). Of course, a wine that had been cellared as long as my "ruined treasure" had been was obviously old enough that the cork used had been, almost certainly, washed in hypochlorite (bleach) solution rather than hydrogen peroxide as is the practice today. Even if the cork hadn't been "bleached," the wine itself dated from a period when bleach was a very popular cleaner inside the winery. Indeed, altogether too many wineries blithely ignore the repercussions of using any bleach in the cellar.

The other major change has been that the cork industry has become a closure industry comprised of both natural and synthetic-closure producers (see sidebar for closure definitions).

So Where do Closures Come from, Anyway?

As readers may recall, a significant portion of the natural and technical corks come from the Iberian peninsula. Once every nine to eleven years, the outer bark is stripped off the tree, dried, boiled, trimmed, cut into strips from which the corks are punched.

I had the opportunity to visit a new cork-factory in Portugal to get a look at the production of both natural and technical corks (see; WBM, vol. 10, no. 2; February, 2003). I hadn't had a chance to see how synthetic corks are produced. When Nomacorc invited me out to see their expanded facilities in Zebulon, NC, I was glad to go take a look.

The Nomacorc Plant in Zebulon

One of the first things one notices when visiting the Nomacorc factory in Zebulon, NC is the cases of wine bottles that are stacked everywhere in the front offices. Well, to be fair, the first thing I noticed was that it looked like one phase of a

A Modest Proposal Regarding Chlorine in Winemaking? Don't do it! A recent article by Pascal Chatonnet et alia, and published by the Journal of Agricultural Food Chemistry, has been getting a little buzz in the press lately. Despite the comments in other publications, Chatonnet's findings are not really surprising, or even unexpected. So-called "cork taint" can be caused by a variety of means. All one needs is a poly-halogenated phenol and a mold friendly environment. Chlorine is just one halogen; a group of non-metallic elements that include fluorine, chlorine, bromine, iodine and astatine (ununseptium, the as yet undiscovered element with atomic weight 117 would also be a halogen) . If one looks at a periodic table, one sees that the halogens are all in a single column. This means that they all have similar chemical properties (this is a defining characteristic of the periodic table of elements). Thus one should not be surprised that tribromophenol can be metabolized into tribromoanisole by those fungi that can metabolize trichlorophenol into trichloroanisole, or that tribromoanisole smells "corked." Indeed, one should not be surprised if all the tri-halogen-phenols can be metabolized into their respective anisoles. Similarly, although this is less certain, it is quite possible that all the tri-halogen-anisoles have a distinctly "corky" aroma. Furthermore, Chatonnet makes two points that are relevant to discuss here. The first is that Chatonnet and his co-authors found that wines containing trace amounts as small as four nanograms per liter of 2,4,6-tribromoanisole (TBA) have a "musty or corked" character analogous to "cork tainted" wines containing 2,4,6-trichloroanisole (TCA). The second point relevant to this discussion is that TBA is formed in a manner analogous to the formation of TCA; several fungi can metabolize tribromophenol (TBP) to TBA. Chatonnet's group found that removing the TBP impregnated wood didn't really reduce the incidence of "taint" in the winery. Chatonnet hypothesized that the interior environment of the winery could become so saturated with the bromated phenol that it could continue to contaminate wine with the tribromoanisole at levels above the sensory detection threshold for an indefinite length of time. All this means that flouro-, chloro-, bromo-, and iodo- compounds should really be excluded from the winery. My hunch is that the metabolic pathway that transforms trichlorophenol to trichloroanisole would work on pretty much any halide-phenol, chemically, the analogues would tend to react similarly to each other. I would suspect that this would also include sensory (olfactory) perception of the analogues. Any wood product can lead to the formation of TCA. Also, since the threshold for TCA is so low, even a distant source could impact a wine. For better or worse, however, the cork is the wood product most associated with TCA (& taint). The main reason for banning chlorine from the winery is that it takes both wood (lignin) and chlorine to transform TCP into TCA. Winemaking is much too intimately involved with wood (corks, barrels, but also packaging and the grape-cluster itself) for one to suggest that all wood-products be banished from winemaking. That leaves the other half of the TCA equation and makes it all the more imperative that chlorine be banned from the cellar. I would never suggest that corks are the only source for TCA contamination. Chlorine in the presence of pretty much any wood product can lead to the formation of TCP, which in turn can lead to TCA. This includes, barrels, woodchips, old pallets, filter pads, cardboard boxes (old wine cases), but also includes the very fabric of the winery building itself. There have been a few, notorious, examples of this latter point of TCA-contamination in recent years. Beaulieu, which was excoriated in the Wine Spectator last year for having a taint problem, is just one recent example. For more information on the formation of TBA, see: Chatonnet, P. et al. Identification and responsibility of 2, 4, 6-tribromoanisole in musty, corked odors in wine. Journal of Agricultural Food Chemistry, published online, doi:10.1021/jf030632f (2004).

construction project was just finishing, but since that was the reason I was there, that wasn't altogether surprising. No, it was the wine bottles that really caught my eye. To me, they indicated several things, first that the company was growing so fast that even the latest round of construction hadn't quite caught up with their needs. It suggested that they do a lot of quality assurance testing at Nomacorc.

According to Nomacorc CEO Marc Noël, "The biggest advantage [we have] over our competitors is the technical know how in processing and formulating our products. Our technological advances are substantial and require a major financial and knowledge commitment.

 Synthetic Closures--Extruded or Molded

At the most basic level, and excluding screw-caps, a synthetic closure is a cork-shaped plastic plug. It isn't really that simple, however. Cork itself has a number of physical characteristics that are difficult to mimic. It's compressible, but quickly re-expands and maintains a seal as long as it stays wet. This means that the polymer, and all examples of these closures on the market are polymers, has to be fairly spongy. Making a spongy polymer can't be too much of a black art, given the large number of foam products on the market. It seems that the tricky part is getting a polymer that is compressible enough to get into the bottle, but resilient enough to form, and maintain, a good seal.

I can't really discuss one aspect of the polymer-foam, the polymers themselves. Even though they all tend to use the same base ingredients, most are made from the hydrocarbons in oil, gas and coal, there are a lot of possible plastic polymers. Just the thermoplastic polymers include several families of compounds including olefins, polyurethane elastomers and vulcanisates, and this doesn't even include the various copolyamides and copolyesters. The exact formulations of the various polymers used by the synthetic closure industry are jealously guarded trade-secrets.

Production of
Synthetic Closures

No matter the exact formulation of the plastic involved, There are, essentially, two ways to fabricate a synthetic, in-the-bottle, closure. One can either inject the polymer into a mold or extrude it from a tube. In both processes, there is a drop in the pressure experienced by the molten polymer that causes gas dissolved in it to expand thus forming the "tiny bubbles" of the foam product.

In injection molded closures, this expansion occurs as the polymer is shot into the mold. Since the newly-formed closure then has to be removed from the mold, this method is really a high-speed batch process. The use of a mold however, means that the manufacturer can control the shape of the product and include features like beveled ends without increasing the number steps during manufacture. Since contact with the mold puts a "skin" on an injected foam product, one should note that there tends to be little or no migration of wine into an injection-molded synthetic closure.

Nomacorc wasn't the first synthetic closure manufacturer, (Supremecorq has been on the market almost a decade longer), but their manufacturing approach was different from the other synthetic closure manufactures on the market at the time in that the Nomacorc is extruded rather than injection molded. The closures start out as dry ingredients which are mixed together and melted under pressure. This causes gas to become dissolved into the molten plastic polymer. The molten polymer is then pumped to an extruder. The polymer experiences a sudden drop in pressure at the extruder, this causes the dissolved-gas to expand rapidly, thus forming a foam-matrix within the plastic. The extruder produces a continuous "rod" of plastic.

The Nomacorc is formed by a two-part co-extrusion. This means that a outer layer is extruded as a tube directly over the inner core. Originally, Nomacorc used two extrusion-heads per production line. However the new equipment installed as part of the expansion uses a more complex extruder that forms both layers at the same time. The new production lines run at just a little less than twice the speed of the original line, producing about 30,000 closures per hour per line.

Since the molten plastic is really quite hot, it needs to be cooled before it is cut into closures. This is achieved by running the "rod" through a water-bath. The "rods" at Nomacorc are actually looped around to the start of the water bath a couple times so that they actually make three trips through the cooling water. After cooling, the "rod" is cut up into closure-sized lengths. This is done in a rotary guillotine. Since a straight and clean cut is needed, the motion of the polymer through this machine is something like a movie-projector with the polymer "rod" stopping every one-and-three-quarter inches so that it can be cut.

The newly formed closures are then finished using a proprietary "corona" treatment that aids the adhesion of ink to the closure. They can also be printed and/or beveled. The finishing side of the factory looks pretty much like any other closure factory (see photo previous page).

One of best the features of the Annual Unified Wine and Grape symposium is that it provides a forum for the various industry suppliers to present their latest products. One presentation that I found interesting was that presented by the synthetic closure manufacturer, Nomacorc. Part of the presentation regarded an interesting methodology for evaluating closures. The "scorecard" presented was developed at Robert Mondavi by Patrick Mahaney as a method for evaluating closure performance (see WBM June, 2003, for more information).

One notable aspect of the presentation is that Nomacorc was careful not to present the closure scorecard as a methodology rather than as a report. That alone spoke to the confidence that the company has in the quality of its own product.

This confidence in the product was also in evidence during the other half of Nomacorc's presentation where Nomacorc's position in the overall wine-closure market was discussed. According to the presentation, Nomacorc has 500 customers in more than 30 countries. In 2002, Nomacorc's reported sales were about 400 million closures. This was expected to top 550 million closures for 2003 and reach 800 million in 2004. This would be an altogether phenomenal growth-rate of about 40 percent (37.5 percent between 2002 and 2003; 45.5 percent between 2003 and 2004). Nomacorc estimates that it has a 32 percent share of the synthetic closure market which would give it something on the order of a three percent share of the total closure market. According to Nomacorc's Marc Noël, "[We] want to have about half of the total market for synthetic closures...Our most significant challenges will be to bring Nomacorc to the highest level of quality of any closure, while also being the most efficient and productive manufacturer." wbm