“There is intense debate still about whether screw caps contribute to what is known as ‘reductive’ flavours in wine,” writes columnist RICHARD CALVER.

Surprisingly, 10 years ago 90 per cent of Australian wine was bottled using a screw cap rather than cork, according to the Australian Wine Research Institute.

While there is still a debate about the most appropriate closure for wine, it seems Australian winemakers and consumers have backed the “twist-off” top.

Some of the wine exports headed overseas though, notably to China, still favour cork as that country (and France) have not embraced the screw cap. Like the invention of the shovel, the screw cap is groundbreaking. 

Screw caps offer convenience that cork-sealed bottles can’t match. They are easy to open and (occasionally, on my part) reclose.

If only the screw cap had been available in the ’70s (cue lights dimming and fade into reminiscence). In a house on a hill in Wellington, NZ, that I shared with four others, a friend had brought around an Australian bottle of red wine for us to consume with dinner.

I recall that Australian red wines were often labelled “claret” if they were primarily from cabernet sauvignon grapes and “burgundy” if they were shiraz based. This was before the French started to litigate worldwide to protect the names of the wines produced in specific localities through the system known as Appellation d’Origine Contrôlée. The French have now successfully eliminated the “theft” of their important wine regions’ names. 

But back to NZ and the red wine, I believe a “burgundy”: it had a cork and our household did not own a corkscrew.

This was a household of young professionals absent tradie skills. So one of our number decided to pierce the cork with a skewer. This was not very successful with the constant skewering shredding the cork and a cork-filled dribble happening when it was time to pour the wine.

Eventually we strained the wine through a sieve into a bowl and from there into glasses. It didn’t matter though; even having regard to its troubled passage into the glass, it was as rough as could be. 

It wasn’t that the wine was contaminated by the cork (in pieces in the sieve with tiny pieces floating in the wine bottle). Cork taint is usually derived from a smelly chemical known as TCA, or trichloroanisole. 

It makes the wine smell of mouldy cardboard or wet dog and infects the wine with the same taste, depending on the levels of its presence. It is a virulent chemical and some wineries have had to be refurbished where TCA has affected wine barrels, drainpipes, wooden pallets and beams or rubber hoses.

It occurs when fungi or mould that is naturally present in the cork or wood comes into contact with chlorophenols that are formed through the combination of phenols in the wood and contaminants containing chlorine. The fungi then converts the chlorophenols into TCA which spoils the wine. Screw caps don’t suffer from this problem.

But there is intense debate still about whether screw caps contribute to what is known as “reductive” flavours in wine.

The argument goes that a properly applied screw cap totally seals out oxygen. But a cork permits some to pass. Hence, reductive characteristics, such as the build-up of sulphide aromas, are diminished in cork-finished wines through the chemical mechanism of aeration.

Hence some wineries, like Burge Family Winemakers in the Barossa, use cork on its premium-grade wines for export and because in transit if a screw cap is knocked the cap’s integrity may be lost.

Libbi, cellar-door manager at BFW told me: “For us, there just wasn’t enough research on what our wines were going to do under screw cap over a period of time and for logistics, with our A-grade corks, they travel better than screw caps.

“For reds they also love that little bit of breathing that screw caps can’t do.” 

Richard Calver has written the CityNews column since 2016.