Is the cork a “dead” closure for wine bottles, and will it be replaced by the screw cap?

wotwine? explains and finds that the diam cork is the best for supermarket wine:

Over 70% of the wines we taste from supermarket shelves are now sealed with a screw cap. The few that come in wine boxes and tetra packs aside, there are around 5% sealed with plastic “corks”, and the rest have various forms of real cork closure; some the traditional pure cork and some a composite processed cork mostly from a company called Diam.

Image result for diam versus cork

So why has this love of the screw cap taken over from the cork which had been the preferred method of sealing wine bottles since the 1600’s?  After all, cork has wonderful elasticity which keeps a good seal in a bottle for many years, and allows a wine to age gently. It is also probably the most environmentally friendly way to seal a bottle.

Corked wine

Everyone has heard about ‘corked wine’ and it is often difficult to recognise. It is nothing to do with bits of cork floating around in the bottle, as one customer service person in a supermarket observed when we tried to return an astringently smelly badly ‘corked’ bottle;  “….I can’t see any cork pieces in the wine”!

But it is the prevalence of cork taint that has led to the development of many new closure types.

The cork industry admit to around 1% of bottles suffering from taint, but it has generally been accepted that this figure is more likely to be between 5 and 10%, and from wotwine’s tastings of over 15,000 bottles we put it at a very high 18% for bottles closed with pure cork, which quite frankly is totally unacceptable.

We do have to bear in mind that we are tasting many inexpensive supermarket wines which have inexpensive corks, and the cork industry have done a great deal to ensure that top quality corks for expensive bottles do not have taint problems. That said, if you were given or had bought a great bottle worth £200 only to find it “corked”, even if only one in a hundred times,

you might not be that happy. With this then, we can see why the supermarkets have supported the screw cap as a closure method that doesn’t have these problems and will lead to happier customers with less returns.

What causes the taint?

The taint which often comes from cork, but by no means is exclusively caused by the cork is the presence of the chemical compounds 2,4,6-trichloroanisole (TCA) or 2,4,6-tribromoanisole (TBA) in the wine, which in many cases will have been transferred from the cork, but which also can have come from other sources in a winery or packaging plant.

TCA and TBA are compounds which do not occur naturally but are created when some fungi are treated with chlorinated phenolic compounds, which are a type of antimicrobial agent used in the preserving of wood.

All you need to know is that TCA is characterised by its smell – sometimes very astringent, but generally of mould or dirty rotting wood. Not only does this pong develop and get worse as the wine gets more air in the glass, it tends to dull down the natural aromas and fruitiness of the wine. Some people are more able to detect these smells than others, but the dulling down of the wine will be noticeable to most people certainly when tasted against a bottle which is not “corked”. TBA is much more pernicious in that it is less obvious, but does again leave the wine flat and dull, without aroma and fruit.

Using the screw cap as an alternative

As you would guess with such high levels of corkiness in the wines we taste, we are keen on good alternatives and the screw cap is generally very good, with the bonus that it is very easy to reseal if you want to stick the unfinished bottle in the fridge for the following day.

But life is not always that simple, and even though we like the screw cap for its convenience and avoidance of cork taint, it does have its own problems.  The screw cap is very good at preventing air from getting at the wine, whilst cork is more porous to tiny amounts of oxygen. Now keeping oxygen away is generally a very good thing, allowing slow ageing and keeping a wine fresh. However modern winemaking is often very protective against oxygen, keeping fresh fruity flavours. But wine also contains volatile sulphur compounds which need oxygen molecules to bind or combine with them otherwise there is the danger of sulphur-y smells. In the industry these are called “reductive” smells and can be anything from rotten eggs, over-boiled cabbage, and often in red wines the smell of burnt rubber tyres.

With “corkiness” a wine is either corked or not, there is no such thing as “slightly corked”.  Someone once said it is a bit like “there is no such thing as being slightly pregnant!”   Reductive smells on the other hand can be very mild and blow off with a little swirling around the glass and oxygenation leaving a lovely wine, or they can be persistent and make the whole drinking experience horrible.  The wotwine? tasters have found that 20% of wines with screw cap have some reductive smells, and 5% are positively pongy.

So “HELP!” we hear you cry, where to go for wine in tip top condition?  There are wines sealed with plastic corks, but these are not great as we have found some let in too much air, particularly over time, and with temperature variations in the supermarket the wines become oxidised. There are some wines now being sealed with a glass stopper although very few appearing on the shelves in supermarkets as yet, but these look promising.

Diam corks

Salvation is at hand in the form of an agglomerate cork made by a company called Diam.   These corks claim to be free of all perceptible taint, to be as elastic and long living as pure cork, and they allow enough oxygen molecules into a bottle to allow gentle ageing and less chance of reductive pongs.  We are cynical about the marketing bumph , but have found after three years of tasting, that these claims are true.  Bravo Diam!

In short, we love the Diam Cork! We have found no cork taint and negligible instances of reduction in any of the wines tested that have been sealed with a Diam cork. We also love to be traditional and maintain the romance and anticipation from using a cork screw to pull a cork.

Look out for Diam corks, they are generally branded on the top or side and they are great.  They are generally pretty compact so a little difficult to stick back in the bottle, but this can be another good thing as you’ll need to ask a few friends around to ensure you finish the bottle!

So what of pure cork?  When it is top quality cork it is still great and most of the Portuguese and Spanish wines wotwine? taste are using pure cork, some better quality than others.  After all, this is a big agricultural business worth supporting if we can get good un-tainted cork, and most cork comes from the Iberian Peninsula, so you would expect the local wine producers to be loyal.

Very top wines  are generally stoppered with very high quality pure cork which is far less likely to have taint problems. If the cork lasts 50 years, is a less than 1% cork taint problem acceptable?  Probably, just.

However there is an increasing number of top wines experimenting with and even deciding to use alternatives – but we somehow  doubt that we will be drinking Chateau Lafite out of screw cap bottles in the near future!

THE WOTWINE? TEAM, February 2017

Postscript; As we buy all the wines to taste, we often take back faulty bottles virtually full with the original cork and with the relevant receipt. We explain the fault carefully and we have found the supermarkets to be excellent in replacing the offending bottles. We also make a note of the “lot number” of the bad bottle and let the supermarket head office know of our findings.