Screw caps for wine bottles were introduced in 1959, but they were initially
associated with value-oriented jugs of wine. Some years later, around 1970-1980 the screw cap was used in Australia for mid-quality products. That image started to change in early 1990’s, when commercial winemakers in New Zealand and Australia started using the screw caps much more widely for all kinds of wine, including some higher-end bottles. Though the old world is still bit “afraid” to make the next step and use screw cap in fresh young wines, only in the last years producers have started launching high quality wines in screw cap sealing.
Of course, natural cork, is and will be the most recognized method of wine closure in the world due to the huge tradition over centuries, but also because of the mostly good impact of it on wines.
On the positive side of cork use, is that cork is a renewable resource. Cork is derived from the bark of Quercus suber, also known as the cork oak tree.
The majority of these trees grow in Portugal and Spain and are abundant and strictly protected. Cork oaks regenerate their outer layer of bark, which allows them to be harvested for the first time at 25 years and after that, is harvested once every 9 years. With a lifespan of 170 - 200 years, one tree can provide cork for thousands of bottles, which makes it the most ecologically sound material to seal a bottle.
Another key point is that thanks to its elasticity, cork expands within a bottleneck to seal the liquid in and keep oxygen out. Its tiny pores, however, allow minuscule amounts of air to interact with the wine, which can transform the aroma and flavor over time. This makes cork the top choice for producers of age worthy wines.
Last but not least, there is something emotional and ceremonial when it comes to the popping a wine cork when we open a wine bottle. This sound is part of the pleasure of wine tasting and as much hard is to believe, the popping sound can make the wine tasting experience even better!
On the other hand, the cork use has some potentially negative impacts on a wine. Cork is susceptible to cork taint. The chemical compound 2,4,6-trichloroanisole, or TCA, affects mostly wood-derived materials, which makes it cork’s worst enemy. It’s caused when chlorine comes into contact with certain fungi during the cork’s processing. While harmless, the compound can transfer to the wine and cause aromas of wet cardboard, damp basement or wet dog. Known as “cork taint,” or simply being “corked,” studies have estimated that TCA affects 3 – 8 % of wines under cork.
As you can imagine, cork is a natural product, and each one is slightly different. Cork brands and their porousness vary, which affects the rate at which air interacts with the wine in the bottle. Even though winemakers choose corks carefully, there’s always an element of the unknown.
One more considerable drawback of cork is that it is made from wood, which dries out and crumbles with time. Wines cellared for long periods of time must be kept on their sides to keep the cork damp. But even with careful cellaring, how many of us have found the remains of a crumbled cork out of our wine after it breaks on its way out of the bottle?
After all, depending on the quality and brand, natural corks can be up to three times as expensive as screw caps, which can drive up the final price of the wine.
But what about the screw caps? Which are the positive and which the negative elements of their use as wine bottle closures?
In the first place, a wine bottle with screw cap is easy to open. Screw caps open with a simple twist of the wrist. There’s no need for any gadgets beyond a free hand and a little muscle.
Very essential is that there is not the danger of the cork taint. In other words, the risk of contamination by TCA from the sealing is zero.
Relatively with the oxygen, the screw cap keeps the bottle sealed and does have a very low permeability to oxygen, so the wine can preserve its freshness and its varietal aromas. Today you can buy screw caps with calculated levels of “oxygen ingress” overtime.
As said above the cost of a high-quality screw cap is in most of the cases less than of a natural cork.
At the same time, there are some negative impacts of the use of screw caps, like the negative environmental impacts. Screw caps are made from aluminum, which is often produced from a strip-mined ore called bauxite. Processing aluminum can be a dirty process, negatively impacting the air and water and generating about 70 million tons of waste annually. Aluminum is non-biodegradable, and though it can be recycled, it’s suspected that most screw caps end up in the trash, and individual waste management companies have their own internal guidelines on whether or not screw caps are accepted as recyclable. Their plastic liners, if not removed, can also make recycling impossible.
When a wine is sealed by screw cap, then it can be prone to reduction. The opposite of an oxidized wine is a reductive one, or a wine in which there is minimal contact with oxygen during the production process. This can happen when a wine’s sulfur dioxide levels are too high and is characterized by rotten egg/oniony aromas. The topic of reduction in screw-capped wines can be divisive, but it’s generally agreed that the plastic-lined seal itself doesn’t cause these undesirable characteristics.
Another drawback of using screw caps is that specific bottles are required as well as specific capping machine.
Concerning the aging ability... cork versus screw cap aging has passionate advocates on both sides. Cork proponents say that the interaction between wine and oxygen facilitated by the naturally porous material is essential to the aging process of a cellar worthy wine. Screw cap fans think otherwise, though neither side has proved their enclosure is better.
To summarize, most of the “modern” winemakers prefer screw caps for fresh white wines and for red wines meant to be drunk young.
On the other hand, natural cork should be used for more complex wines such as white and red wines that have been aged and they could still evolve in the bottle.