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Screw Caps Vs Cork:

Closure on the Debate

We used to judge the quality of a wine based on whether it was sealed with natural cork, synthetic cork or screw cap. Any wine that didn’t use cork was instantly regarded as inferior.

So, why do winemakers choose to seal wines with closures?

 

Natural cork

Natural cork has been the wine seal of choice for thousands of years. Remains of amphoras sealed with cork have been uncovered in the ruins of Pompeii. The majority of modern day cork comes out of Portugal and is still the wine stopper of choice in the 'Old-World'. Portuguese cork harvesters are called ‘Tiradors’ and are one of the oldest trades in Portugal.

The reason cork has been so important to the wine industry is due to cork being semi permeable. This means a very small amount of oxygen is able to penetrate the wine. This is important for 'fine' wines as the slow ingress of oxygen assists with the ageing process.

Cork, however, can also taint the wine with flavours that are less than desirable. Cork taint has always been a problem for wine consumers as certain types of mould, although unseen, can be present within the cork. The mould is usually present in the bark, but can also be released during the bleaching process.Also, the fact that no two corks are the same consistent size can mean the difference between one wine becoming ‘corked’ due to too much oxygen ingress or just enough. Cork taint is the leading cause of damaged wine.

The fact no two corks share the same consistent size or density can mean the difference between one wine becoming ‘corked’ due to too much oxygen ingress or just enough. Cork taint is the leading cause of damaged wine.

 

Synthetic/ plastic cork

Synthetic or plastic corks have risen as a viable and cheaper alternative to natural cork.

While a cheap and viable alternative to natural cork the synthetic cork’s issue centers around the lack oxygen intake into the wine which therefore makes it undesirable for any wine which is meant to age more than a year in the bottle. On the flip side, the main benefit of synthetic cork apart from not causing cork taint is the integrity of the structure; it's not prone to degrading and crumbling so there won’t be any floating cork in the wine after you’ve opened the bottle.

Castelli cellar hand preps the corks for bottling

Screw cap

A new era of wine sealing has brought us the screw cap. Quickly overtaking cork as the sealer of choice in Australia and New Zealand, it's hard to find a wine sealed under anything else.

Initial arguments against screw caps centred on two key points:

  1. Screw caps were supposed to be an indication of poor or low-quality wine; and
  2. Screw caps were supposed to allow oxygen ingress.

 

However, both these arguments were proved false. In 2010, the Australian Wine Research Institute released a study showing the same wine being sealed with each of the different sealers and leaving the wine to age for over a decade. The results showed the wine under the metal screw cap as the most well-preserved wine.

Screw caps also stop the majority of faults in a wine developing. Faults like TCA (Trichloroanisole) are eliminated with the use of screw caps. They’re also cheaper and far more consistent than cork.

 

Glass stopper

Generally accepted as being equally efficient at preserving wine as metal screw tops. A glass stopper is quite an illustrious option for bottle sealing. It is credited as controlling the ingress of oxygen, not causing cork taint and is an elegant option. Glass stoppers are also able to universally seal different sized bottle shapes making it a ‘one size fit all’ option for winemakers.

The major problem with this solution is the cost. Glass stoppers cost considerably more and special machinery is required, this limits their use.

While some premium Australian wine producers still use cork for its traditional merits, much of our industry has gone the way of the screw top. Now we wait for the world to follow.

www.awri.com.au/

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Warramunda Estate Liv Zak 2013 Cabernet Sauvignon
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Warramunda Estate 2014 Cabernet Sauvignon