The Taming of the Screwcap

By Dr Jamie Goode

Screwcaps v Cork - This is still a much debated topic and could probably lead to divisions between friends over the dinner table!?  This is why the IWFS believes that this is an essential topic to be given a balanced and fair airing and author Dr Jamie Goode was felt the ideal person to write it, bearing in mind the research he has done on this.   Jamie explores the many options that have been trialled and launched over the years and explains the factors influencing their success or failure. The aim is to give clarity to those with a keen interest in exploring the various quality influences on the wine in the bottle. Jamie said “The issue of wine bottle closures runs the risk of being highly controversial, or highly technical and boring, and I've tried to avoid both in this book. It's my hope that this is a readable, impartial treatment of the topic that will be a useful reference.” It could well still leave the question – which closure is best?  Maybe the jury is still out.  

• Language: English
• Publisher: International Wine and Food Society
• Release date: Oct 6, 2021
• ISBN: 9780900813054

Book preview

Introduction

This is the story of how screwcaps have cornered nearly a quarter of the global market for wine closures

Who would have thought that the wine world could have been so polarised – and ultimately transformed – by something as simple as an aluminium closure? While the story of the screwcap is far from finished yet, already it has been a remarkable one. This is the subject of this monograph.

First, we will consider the importance of the closure, and we will begin with examining how closely it is entwined with the very definition of wine.

What is wine? On one hand we have the legal definition: wine is made from grapes, freshly crushed, with only limited additions and processing aids permitted. But on the other hand we have the functional definition, one that resonates more closely with most drinkers. Wine is an alcoholic drink, made from grapes, that comes in a bottle, sealed with a cork, which we drink in particular settings. The cork, and the implement used to remove it, the corkscrew, are fundamental to many people’s conceptions of wine. In part, this explains the resistance that screwcaps have met with across large swathes of the wine-drinking globe, even though they potentially offer the solution to one of the biggest frustrations for wine drinkers: bottles spoiled by cork taint.

Screwcaps potentially offer the solution to one of the biggest frustrations for wine drinkers: bottles spoiled by cork taint

This monograph examines the rise of screwcap use in wine. It looks at the technological issues surrounding the use of screwcaps, and places these in the broader context of wine bottle closures. Critically, there are two important issues that must be explored. First, how does the screwcap affect the flavour of the wine that it seals, if at all. Second, how does wine bottled with a screwcap age and develop over time.

We will examine the current, rather polarised situation with closure choice and cast an eye to the future. On the way we will grapple with some rather technical subjects, such as post-bottling wine chemistry, but an understanding of these is intrinsic to the screwcap story.

The overall picture

To begin with, let’s travel back 20 years. If you were to buy a bottle of wine, it would almost certainly be sealed with a natural cork. What’s the situation today? It’s hard to get exact figures, for the obvious reason that no-one is collecting these data systematically. However, most closure companies will do market research that allows them to come up with an estimate. The latest estimates are that the global market for bottled wine is around 18.5 billion bottles, and of these, around 4.5 billion are now sealed with screwcaps. This figure is growing, but just how far it will grow is anyone’s guess.

How has the screwcap seized so much of the market in such a short space of time, in what is a fairly conservative industry? This will be the subject of the first chapter.

I: A brief history of wine closures

With the incidence of cork taint becoming ever more obvious, closures invented for the spirits industry trigger interest among producers in Australia

Cork has been used to seal wine bottles since the 18th century. Before this time, wine was shipped in barrel. If bottles were used to serve this wine, it would only stay in bottle a short time, so there was no real need for a closure in the modern sense. It was only by the 18th century that glass bottles became affordable enough for wine to stay in them for extended periods, and it was cork, with its elasticity and relatively inert nature that proved suitable for sealing these bottles.

With the advent of corks driven into the bottle came the need for a device to remove them: the corkscrew was the solution. Things pretty much stayed this way until the 1990s, and considering the serendipity of its discovery, cork did a pretty good job. Indeed, it’s only since alternative closures have been tried that we’ve come to realise that sealing a wine bottle is not a straightforward business if you want the wine to develop in a wine bottle in a pleasing way. More on this later.

But cork has problems. As a natural material its structure varies, and more worryingly, a certain proportion of corks – these days reckoned to be around 3.5%¹ – carry a taint that spoils wine.

The compounds responsible for cork taint produce musty off-odours which are detectable at tiny concentrations, and are caused by fungi present in the cork bark, even in the cork forests themselves. These musty taint compounds can also increase in level if various steps in the processing of the cork bark are not carried out carefully. For example, the old fashioned method of washing the planks often led to tainted cork, as did the practice of storing the planks on bare earth before