To Cork It, Or Not to Cork It?

To Cork It, Or Not to Cork It?

Chances are if you’re read­ing this blog, you have at least heard of Dom Perignon, if not the man, then at least his legacy in the pres­ti­gious Cham­pagne com­pany of the same name. Dom was a Bene­dic­tine monk, and con­trary pop­u­lar belief, this monk did not dis­cover the in-bottle sec­ondary fer­men­ta­tion tech­nique respon­si­ble for the car­bon­a­tion found in ‘sparkling’ Cham­pagne wines like Dom Perignon. He did, how­ever, invent some­thing wine-related—the cork—at least, he invented using it in wine bot­tles. The ear­li­est known usage of cork (as a stop­per) was by the ancient Egyp­tians; Dom, how­ever, intro­duced this method for stop­ping wine in the 1600’s. Up until his inno­va­tion the accepted method for cork­ing wine bot­tles was to use wooden stop­pers wrapped by olive oil soaked hemp, and these were prone to pop­ping off. Dom rev­o­lu­tion­ized the indus­try; the wide­spread accep­tance of cork even lead­ing to stan­dard­ized bot­tle openings.

Cork Clas­si­fi­ca­tion

Cork comes in seven degrees of qual­ity. The qual­ity depends on the mate­ri­als used and the pro­duc­tion process adopted by the man­u­fac­turer. High qual­ity cork is made from oak trees, and nowa­days most cork comes from the Oak tree Quer­cus suber, which is often found in the oak forests of Por­tu­gal. There are also less-natural corks that, instead of being made from oak bark, is made from dust and bind­ing agents.

The cork type usu­ally dif­fers for for­ti­fied, sparkling, and still wines. Let’s have a look at a few examples.

A stan­dard cork — Is usu­ally com­prised of a sin­gle piece of bark about 24mm in diam­e­ter, which is about 6mm wider than the diam­e­ter of the neck of the aver­age wine bot­tle. This ensures a tight fit so that the cork does not dry out and con­tract.

An agglom­er­ate cork — Is basi­cally tiny pieces of chopped cork all bound together by glue. It is the bud­get stop­per made from the waste mate­ri­als of other, higher qual­ity corks.

Cham­pagne corks — Are often made from a sin­gle base of oak, with the top/crown crown being com­posed of granules.

The Dan­gers of Cork?

There is a gen­er­ally accepted fig­ure of around 1–5% of cork-bottled wines fall vic­tim to what is known as ‘cork taint.’ Although not always the cause, the main cul­prit for this is a chem­i­cal by the name of TCA (2,4,6-trichloroanisole) which, upon con­t­a­m­i­na­tion of the wine, basi­cally ren­ders the native tastes and aro­mas to that of a wet paper bag, a wet dog, or damp base­ment. Because of this unde­sired con­se­quence to cork, some vine­yards are switch­ing to alter­na­tive forms of bot­tle stop­ping. We will explore those now.

Zork® , Vino-Seal® , and Crown Caps

There are a few lesser-known alter­na­tives to wine clo­sures. Zork® is a com­pany in Aus­tralia that designs and man­u­fac­tures alter­na­tive clo­sures meant to screw like a screw, but also pop like a cork; they are also able to be resealed, truly com­bin­ing the best of all worlds, save for a slightly higher cost. Crown caps are the tra­di­tional bot­tle cap that you might find on a beer bot­tle. They offer an excep­tional seal, but the down­side is that there will no oxi­da­tion at all, and, usu­ally asso­ci­ated with sparkling wine type vari­eties, crown caps elim­i­nate some of the fun and cer­e­mony of pop­ping open a bot­tle of ‘bub­bly.’ Finally we have Vino-Seal® (Vino-Lock® ) a plastic/glass enclo­sure released by Alcoa. It has been around since 2003 and around 300 winer­ies have uti­lized Vino-Seal. The down­sides are a pretty high cost (70 cents per clo­sure), the fact that the her­metic seal will com­pletely stop oxi­da­tion, also the cost of man­ual bot­tling, as auto­mated equip­ment does not exist out­side of Europe.

Syn­thetic Closures

Syn­thetic clo­sures like the one below were designed to address the TCA prob­lem. Stud­ies like the one done in 2007 by the Vic­tor Segalen Bor­deaux 2 Uni­ver­sity show that injected molded corks offer the low­est pro­tec­tion against the oxi­da­tion of the wine, and post-bottled oxi­da­tion will neg­a­tively impact the aroma and taste. Often times the phys­i­cal nature of the syn­thetic stop­per will also con­tribute to reports of a slight chem­i­cal taste. In time frames longer than 10 years syn­thet­ics were observed by a French study as start­ing to dete­ri­o­rate as opposed to their nat­ural cousins who did not show this same dete­ri­o­ra­tion. It should be noted, how­ever, that advanced, next-generation nano-technology stop­pers built to repli­cate the cel­lu­lar struc­ture of actual cork, aim to han­dle oxi­da­tion bet­ter than their previous-generation coun­ter­parts by sim­ply copy­ing the nat­ural prop­er­ties of real oak bark.

Stelvin® Screw Caps

The most widely known form of screw cap used in wines is a brand devel­oped by the Rio Tinto Alcan com­pany (recently sold to Amcor) called Stelvin®. The brand is so com­mon that the name ‘Stelvin’ has taken on house­hold con­no­ta­tion, with many peo­ple, even in the wine indus­try, refer­ring to any screw cap as a ‘Stelvin clo­sure’ regard­less of the brand. There are some dis­tin­guish­ing fea­tures which dif­fer­en­ti­ate Stelvin® from the other com­pa­nies includ­ing a long out­side skirt, and the use of a PVDC (polyvinyli­dene chlo­ride) as the neu­tral liner on the out­side or the inside wadding. Unlike syn­thetic clo­sures, screw caps offer the high­est degree of oxi­da­tion protection—so much so that it has been accused by wine crit­ics like Jan­cis Robin­son of attribut­ing to reduc­tion, the oppo­site of oxi­da­tion. Some­thing espe­cially affects wines like Sauvi­gnon Blanc. Instead of too much oxy­gen get­ting into the bot­tle, reduc­tion is when there is not enough. The oxi­da­tion process is, of course, respon­si­ble for cre­at­ing some of the depth and com­plex­ity in wine after it has been bot­tled. Not enough oxy­gen and the wine may taste ‘too fresh,’ not hav­ing devel­oped some of the taste com­plex­ity that comes with a period of oxi­da­tion. Still, Stelvin screw caps have caught on sig­nif­i­cantly in New Zealand, with approx­i­mately 70% of the wine bot­tled in 2004 being bot­tled with a screw cap, up from 1% in 2004.

Deci­sions, Deci­sions, Decisions

‘Cork taint’ is kind of a mis­nomer because the cork itself does not affect the wine. The cork becomes con­t­a­m­i­nated with TCA which passes through to the wine. And not all wine con­t­a­m­i­na­tion is caused by TCA, as there are many other ways your bot­tle can lose that mag­i­cal taste; fur­ther­more, not all inci­dents of TCA con­t­a­m­i­na­tion can be attrib­uted to the cork itself. TCA can actu­ally be found in bot­tled water, screw top wines, beer, spir­its, soft drinks, etc. That said, how­ever, the inci­dents of TCA con­t­a­m­i­na­tion have proven to be lower in screw top and syn­thetic stopped wines.

So where do we stand?

Well, the most impor­tant vari­able in the wine stop­per equa­tion is the time frame that most wines are intended to be con­sumed within. To the point, around 95% of wine is made to be drunk ear­lier than later. In other words, the post-bottling oxi­da­tion ele­ment we talked about in the last sec­tion will likely not apply, in which case a Stelvin top seems to be the most log­i­cal option.

There has been a lot infor­ma­tion pre­sented, so let’s look at a quick sum­mary to wrap things up:

1.  Tra­di­tional Oak Tree Cork — The clas­si­cal vin­tage look and taste; cul­tur­ally accepted world­wide. There is slight chance your bot­tle will suf­fer from con­t­a­m­i­na­tion, but with TCA affect­ing 1–5% of wines, chances are you have noth­ing to worry about. Bor­deaux and other oxidation-reliant wines will improve in taste-complexity over time.

2.  Syn­thetic — Not as good for oxi­da­tion, more or less fail­ing com­pletely at 10 years. Much less of a chance of TCA con­t­a­m­i­na­tion. Ade­quate, with next-generation alter­na­tives com­ing down the line.

3.  Stelvin — Offers the best pro­tec­tion against wine spoilage, will give a con­sis­tency from one bot­tle to the next, and will best pre­serve the aro­mas, flavours, and oth­er­wise fresh­ness of the bottle—plus it’s just plain easy get off, and to put back on.

4. The Oth­ers — They are used far, far less, and in the con­text of oxi­da­tion, achieve the same func­tion­al­ity as Stelvins.

It would seem the jury is still out on the ben­e­fits of cork vs. Stelvin, but it looks like we will be see­ing more Stelvin-type screw tops as vine­yards and winer­ies are begin­ing to break from dogma and rec­og­nize that many wine enthu­si­asts a want fresh­ness, con­sis­tency, and the best pos­si­ble taste.