How to Understand Wine
Bottle Stoppers: Cork Taint, The Discovery of the Cell and Oily Activities
The way we seal wine has changed over the years…
For hundreds of years, humans have been using cork to stopper up wine bottles. But how did this system come into being and what did we use before? This article walks you through what went on and explains why cork became so dominant. Warning: some of this is pretty weird…
The History of Cork Usage: Rags, Resins and Rocks
Cork is a large factor in how well a wine ages, but it has not always been used. In the Ancient world, the Egyptians primarily used reeds in clay to seal up the huge clay amphorae they would use to store wines.
The ancient Romans were the first to use cork to stopper their containers, but over the ages lost this practice. The cork used in bottles, Quercus suber, is primarily grown in the cork forests of southern Portugal, and is not reusable once the plug has been pulled out. The combination of distance from Rome and unsustainability made the material unfavoured by Romans, who stopped using it. Instead, they took the easier and cheaper route of plugging their clay bottles and wine sacs with stoppers of rags soaked in olive oil, or wooden plugs sometimes held in place by sealing wax.
The Romans also used different kinds of resins to seal their vessels, and the effects of different resins on flavour was well-understood before the effects of different woods were. Whole treatises have been written on the benefits of pine resins, for example. Cork, after all, doesn’t offer the same flavour enhancement to wines as resins do — and the added flavour was, by all accounts, greatly needed to soften the sickly-sweet, syrupy Roman wines.
However, resins, reeds, oils and rags were very poor at preventing oxidation, which causes the alcohol in wine to form acetic acid, also known as vinegar. This led to more unusual methods being used. German winemakers put rocks into barrels to raise the level of liquids and reduce the amount of air. Many winemakers put olive oil or resin directly into the wine containers as well as using it to seal the opening. The oils would float on the top of the wine, and prevented the wine coming into contact with the oxygen in the air. However, after a certain period of time this oil would turn rancid too. When serving, cotton or cloth was dipped into the container to absorb some of the oil, and a small glass was then poured to remove the oil from the top before drinking could occur. In what is widely believed to be the seminal work on wine storage, the author George Taber states that “the custom of tasting wine before serving started as a way of making sure all the oil was gone”.
“The custom of tasting wine before serving started as a way of making sure all the oil was gone” — George Taber
The Re-Discovery of Cork
However, in the C18th, cork began to be used a stopper again. Who exactly re-started the practice is open to debate. Many sources claim that it was re-discovered by Dom Pérignon in Champagne, who noticed some Portuguese travellers passing through his monastery using corks to stop up their water skins. In fact, it was probably actually one of his contemporaries, Jean Oudart. Jean Oudart was a force in wine technology in the 18th Century, and has been credited both with the invention of the liqueur de tirage and importing the cork Quercus suber from Spain to the Champagne region for use in winemaking for the first time. However, documents detailing his contributions were lost in the French Revolution, so we can never truly know how much credit to share between him and Pérignon.
How does Cork Work?
The short answer: nobody knows. The famous scientist Robert Hooke (1635–1703) was the first person in the modern era to study cork using a microscope. Looking at cork through a microscope led Hooke to coin the term ‘cell’ for the first time, from the Latin cella, which translates to ‘pores’, or tiny room. Hooke’s discovery of cells is widely celebrated throughout biology today and is one of the most important discoveries of all time. Hooke wrote of its structure:
“I could exceedingly plainly perceive it to be all perforated and porous, much like a honey-comb” — Robert Hooke
Hooke also attempted to calculate how many cells were in the tiny slice of cork, and given the routine layout of the sheet came fairly close to the real number. Hooke thought the cells were the pathway for fluids to pass through the plant, but ‘cells’ are now used to describe the unifying structure of biological materials.
It is still not known today how corks works so well at preventing oxidation whilst still allowing tiny amounts of evaporated alcohol to pass through. In theory, the cell walls should prevent any movement of vapours, but as anyone who has bought old bottles of wine and looked, disappointed, at a low shoulder in the neck of a bottle, this is simply not true.
In more recent years, cork has begun to be switched out in many bottles in favour of screw-caps. This was mostly because of Australian demand. These days, 99 in every 100 bottles produced in Australia is sealed with a screw-cap.
Cork Taint and the Carnation Revolution
In the 1970s, the Portuguese cork industry was greatly disrupted as a revolution known as the Carnation Revolution swept through the country. Prior to this point, the country was ruled by fascists who conducted wars with Africa which consumed over 40% of the national budget. Fed up with the poor quality of life and being one of the poorest nations in Western Europe, Portuguese around the country took up arms. The Portuguese economy is centred around the export of goods such as sardines, cork and textiles, and cork became a natural political fighting ground. Fields which had stayed in families for hundreds of years changed hands rapidly, and trees which normally are harvested every seven years were raided by rogue teams roaming the countryside, scythes in hand.
As a result, the premium end of the cork market, which comprises of buyers from high-end wineries, were disorientated. The market was flooded with cork which was artificially bleached with phenols, to create a whiter cork desirable to the high-end houses. A great number of corks from this era went on to develop cork taint, or TCA (2,4,6-trichloroanisole), which resulted in up to 7% of Californian wines from the 1970s developing the fault.
The problem was compounded for Australians: being so far from Portugal, their shipments down under would arrive with cork far lower in quality to many European orders, partly due to the length of the journey and conditions in the ships themselves. The Australians took up arms, and invested heavily in finding an alternative, landing on the screw-cap and solving their problem in one go.
Today, bleaching is heavily discouraged across the Portuguese cork community, although TCA may still appear in corks from influence of fertilisers or fungi living in the cork tree. Cork taint will never be fully solved as long as corks are used, but the risk of a ruined bottle has decreased significantly since the political situation in Portugal stabilised in the 1980s and democracy emerged.
Why Has Cork Remained So Popular?
After all of the early attempts at storage, with floating oils, rocks and rags, we hit on a solution we knew once before but forgot. Even though we still don’t fully understand how cork works to prevent oxidation, we know that by-and-large it is safe to use over dozens of years — although Australians and other screw-cap advocates may feel otherwise!
