The New Synthetic Cork

For the last 400 years or so we’ve been stoppering bottles of wine with cork.

It works, sure, but it does have a few problems associated with it. Natural cork is the bark of the cork oak tree, Quercus suber, which is suitable for use as a bottle stopper because it is compressible, flexible and has insulating properties. It can be cut to fit into a bottle neck and manages to do the thing that wine lovers like — it keeps the wine in the bottle and air out until you are ready to open it.

The down side is that, being a natural product, its purpose in nature is to protect the tree that it grows on. Using it for something other than its intended purpose, it doesn’t always perform to our standards.

Some wine corks leak, have pockets, occlusions, various other blemishes and of course, we have the infamous wine fault of cork taint caused by TCA.

For a long time, we, as consumers put up with relatively high levels of contamination from TCA in wine. This substance is harmless to us, but at higher concentrations, ruins wine by adding musty aromas and flavours like wet cardboard, wet dog and yes, like cork.

Some estimates were that at least as many as 10% or so of all corks had some levels of contamination by the 1980s and 90s. As with any virtual monopoly, the cork producers centered in Portugal, the Mediterranean and to a lesser extent, parts of South America really didn’t care.

The only options were things like plastic or screwcap closures, which didn’t have a good reputation. But as times changed, something strange happened, the screwcap took off led by the popularity of Australian wines and the skyrocketing interest of wines like New Zealand sauvignon blanc. This humble closure started appearing on wines well above the bottom rung and is now common on wines $25, $50 and above.

We also started seeing an improvement of perceptions of plastic corks beyond the simple latex plug we never liked. I was recently the guest of Nomacorc in North Carolina to learn a little more about synthetic closures and was thoroughly impressed by how technology is finally coming to the bottle of wine.

Nomacorc dominates the synthetic cork business, producing over 2 billion corks a year with a patented co-extruded product. There's a lot of technical jargon, but what it is essentially is a foam core surrounded by a rind of a similar, non-foamy plastic resin. The co-extruded part is important since both the core and rind are extruded (much like when you make sausage) at the same time permitting a better bond between the layers. The rind is designed to look like cork (much like a printed wood grain on basement panelling) and provides the support for the core, along with providing the tight seal in the neck of the bottle.

The foam core is where the magic happens though, by various proprietary and secret processes, Nomacorc has been able to produce corks that allow specific, selectable levels of oxygen transfer between the bottle and the outside environment.

Why should this matter?

Wine ages in the presence of oxygen. Wines bottled with too little oxygen become reduced (think of some screwcap wines with animalistic or oniony characters) and wines with too much oxygen show dried out or sherry-like characters. In between, however, are the full range of flavours we like in our wine. A winemaker can select a cork that will permit a certain amount of oxygen transfer. Some wines can use the extra oxygen to soften tannins and open up the fruit and others can benefit from a lower level of oxygen to keep the fruits going and avoid some tired or dried up characters. Notably, it allows winemakers to continue the winemaking process well beyond the time the wine is bottled. By selecting the specific closure, the wine can be at its best when its ideal time to drink has arrived — something natural cork can’t do.

The downside is that no closure is perfect, unless you wanted to buy your wine as sealed ampoules — what fun! A good cork severely limits the transfer of oxygen into the wine and a screwcap which has virtually none, making both of these closures still the ideal for long term cellaring (greater than 5 to 10 years). Cork is probably still better than a screwcap for very long term cellaring, at least for the average wine consumer’s perception. I wrote about this before for Wine Access in the Cork vs. Screwcap Experiment.

The “new and improved” synthetic corks from Nomacorc don’t yet have the data to definitively determine how long they can store and age wine well. Tests are underway with accelerated aging trials, but nothing beats real life, long-term aging. The synthetic corks generally allow more oxygen to pass through than natural corks, meaning at some point, the wine will be overly oxidized and that ideal drinking time will come quicker than with an “ideal” or top quality natural cork.

There are no guarantees in life, not all natural corks are made perfectly and all bottle closures will fail at some point. No wine ages forever, no matter how you store it. Most wine is consumed rather quickly, the vast majority of wines are consumed within days of purchase, the need to preserve it over long time frames is not a concern for most drinkers.

Also, most customers just don’t care if their wine has a bit of tree bark or a piece of co-extruded foam core polymer closing the bottle. By the time the capsule comes off, corkscrew in hand, I promise; your thirst far outweighs your thrill or disappointment of the type of cork.