it may seem extraordinary, but one of the hardest decisions for any winemaker doesn’t concern practices in the vineyard or cellar. Although the implications of picking dates, fermentation temperatures, extraction regimes, barrel selections and so on are all crucial for wine style, it is the choice of stopper that gives producers one of the greatest headaches.

That’s because so many factors are involved in the selection, while the options continue to expand, and the science behind closure innovations is always evolving.

Furthermore, stoppers do affect the way a wine can taste, as well as a producer’s costs and carbon footprint.

the number of wine bottles produced annually totals 18 billion, of which 11.5 billion are sealed with cork, 4.5 billion are closed with screw caps, and 2 billion use plastic stoppers.

The recycling rates are thought to be :

Cork- 100% landfill

Aluminium- 32% recycled, 68% landfill

Plastic- 19% recycled, 81% landfill

The most emotive issue in closure selection is TCA incidence in a wine, a musty smell detectable by humans.Although TCA can be present in packing materials, and winery equipment, it is most commonly believed to enter wine from corks (although it must be present in the part of the cork in contact with the wine, as it can’t migrate through the closure). The number of wines sealed with corks contaminated with TCA is a subject of speculation, but it is widely felt to be at a relatively low level today, having fallen from more than 5% at its peak to below 3%.

In general terms, tests have shown that standard plastic stoppers offer the worst protection against oxygen over time.

 Tin-lined screw caps appear to offer the closest thing to an air-tight seal on the market today, closely followed by a high-quality natural cork

Finally, it should be stated there are many other factors that affect a winemaker’s decision to choose a particular closure type. These include, critically, market preference, as well as issues such as convenience – screw caps, for instance, remove the need for a corkscrew 

But it should be stressed that winemakers today are unlikely to choose one type of closure for all their wines, choosing different stoppers depending on the wine style and target consumer.