David Gleave MW champions the screwcap

Liberty Wines' managing director, David Gleave MW, has long championed the use of screwcaps as a preferred method of bottle closure. Here he explains why.

Terroir is a word much used but little understood. Over the years, I've heard any number of wine faults - reduction, aldehydes, brettanomyces, cork taint - attributed to terroir. This is a pity, for it only serves to perpetuate a myth that obscures one of the great things about wine: true terroir is one of the most exciting qualities one can find in a glass of wine.

There are manifold reasons why winemakers may fail - no matter how hard they try - to capture the character of their site in the wine they put into bottle. Recent tastings point me in two directions. One is too great a weight being given to ideology. The current trend for 'real' wines is a case in point. For the past 25 years, most producers have been trying to diminish the amount of sulphur dioxide (SO2) used in their wines. But producers who try to eliminate the use of SO2 entirely sacrifice its beneficial effects (as an antioxidant and antibacterial agent) on the altar of ideological purity. They also sacrifice terroir, for without sufficient levels of sulphur their wines (on the evidence of tastings over the past decade) develop aldehydes, high levels of volatile acidity and other maladies.

The other factor that all too often inhibits the expression of terroir is cork. There are three reasons for this:
1. Cork taint, which ruins the wine.
2. Scalping. Corks absorb some of the flavours of wine, reducing the aromatic expression of the wine.
3. Random oxidation. Cork is an inconsistent closure. When it works well, it is excellent. But each cork is different, and may form a less than perfect seal that allows too much oxygen into the bottle. Too much oxygen destroys the wine that the winemaker puts into bottle.

All three of these factors inhibit or destroy the expression of terroir. This was brought home to me recently when I did a comparative tasting of the same wines (from the Allegrini family) under cork and screwcap. A week later, I did a similar tasting, comparing the wines from Isole e Olena sealed under these two closures, as well as under vinolok. At the latter tasting, winemaker Paolo De Marchi, who of course has seen the wines - his Chardonnay and Cepparello - at every stage of production prior to bottling, commented: 'I know the flavours I had in the wines when they were bottled. And I know that those flavours aren't being expressed to the fullest extent in the bottles sealed under cork.'

Vanya Cullen of the Margaret River producer Cullen Wines, goes a step further. 'I have converted to biodynamic production in recent years as I feel I get the most vibrant and intense flavours from grapes grown this way. I also think my wines are better balanced since I converted our vineyards to biodynamic culture. As a result, I want to preserve this balance and those flavours in my finished wine, and I think the best way of doing that is to use a neutral closure like screwcap.'

It is my view that restaurant customers will drink better wine if they can 'taste' the terroir in the glass. In order to achieve this, we need to encourage winemakers to capture the character and quality of their sites in their finished wines. If this were the guiding ideology of every winemaker, we would all be drinking better wines.

• Sommeliers