Screw cap or cork? Natural or plastic? The decision on what kind of wine stopper to use is not easy for winemakers. There are many factors to consider from environmental impact and cost to quality and tradition. Moreover, there are a many misconceptions about the various types of corks and caps. Wild claims are made in favor and against each one. But really, what difference does it make to the consumer? Here I attempt to sort through the myths to discover the facts of this confusing subject.
Screw caps undoubtedly provide a better seal than cork but also prevent oxygen transmission, a process that allows wine to breathe and mature over long cellaring. Wine ageing and maturing is known to be a complex and poorly understood process. It takes place in what is called a reductive (oxygen free) environment once the wine is sealed in the bottle. Scientists who have studied this are not sure whether allowing a minuscule level of ‘breathing’ through natural cork makes a difference or not. Because of the complexity and time scales involved, definitive experiments have not been done. Many people argue that for most whites, consumed within one or two years after bottling, it makes sense to use a cork since they are not likely to become ‘corked’ in this short period of time. The subjective nature of wine appreciation is likely to impede any settlement of this debate, but there are more objective issues to consider and it is good idea to have some information than can help you to form your own ideas.
Natural cork, made from the bark of the cork trees, provides the unique combination of qualities that have made it by far the most popular stopper for wine. Natural and renewable, cork trees belong to the oak family and grow predominantly in Portugal and Spain, but also are found elsewhere, such as Sicily, Tunisia, Algeria, Morocco, and South Africa. They live upward of 200 years. To harvest the cork, the trees need not be cut down. Cork bark can be harvested numerous times throughout the tree’s life (although it takes about nine years between sloughing, done by hand with hatchets, for the tree to ready itself again).
Screw caps, on the other hand, provide a very good seal, much more air-tight than cork, thus preventing short term oxidation of the wine. They are also much easier to open: you simply twist them off, like you do with a soft-drink, no need for a corkscrew. A small plastic band tucked inside top of the cap provides the uniform and consistent seal, unlike cork which can be very variable. Screw caps are much more reliable and of course eliminate the risk of a wine becoming oxidized or corked. On the other hand, these metal caps hinder the maturation process that many people attribute to cork closures which allow the wine to ‘breathe’ and mature properly in the cellar, ever so slowly. On a more sentimental note, these flimsy twist-off caps eliminate the ritual of opening a bottle. The twist, pull and pop as the cork is freed from the bottle—a bell sounding the start of a convivial evening. conundrum
The next time you find yourself facing a shelf of wines, think about the occasion and the type of wines you are considering. Heading out for a picnic? You might go for the ease and flexibility of a screw cap. Buying for a birthday or anniversary? You’ll be looking for something special, perhaps a mature wine that has benefited from aging and breathing through a natural cork. Or perhaps you’re looking for a crisp young rose to sip on your deck after a long day’s work; in that case a screw cap or plastic cork will do just fine. The most important thing is to let the stopper fit the wine.
That being said, here’s my little speech in defense of natural cork. The use of this material allows for more than maturation of a wine, it also preserves old-growth cork oak forests and a centuries-long way of life through sustainable harvesting of the bark. And it helps preserve the planet by naturally absorbing carbon, the greenhouse gas responsible for climate change. Artificial plastic stoppers or screw caps on the other hand consume fossil fuels, and use at least five times more energy per ton to produce, before millions of them end up in our landfills and oceans. It may seem like a little thing, but demanding natural cork is something we can all do.
– Soledad Claveria