Getting Closure: Corks or Screw Caps?

various corks and screwcaps
My collection of corks and screwcaps is varied
My studies for the WSET Diploma have begun and the wine geek
in me finds the discussion of brett, malolactic fermentation, lees stirring,
and reverse osmosis just fascinating. The average wine consumer need not concern
themselves with such matters, but a true and deep understanding of wine
production – from vineyard to glass – requires a working knowledge of such
A topic that’s popping up (pun intended! ) a lot, which is
and should be of interest to the wine consumer, is wine closures – those things
used to stop the bottle. There’s much talk, research, and debate about natural cork vs. synthetic cork vs. aluminum
screw cap vs. other options.
The everyday conversation on corks vs. screw caps sounds
something like this: “Wines with a twist-off cap cannot be as good as wines
with a cork,” or “Screw cap wine is cheap,” or “It’s just more sophisticated/traditional/fun/ceremonial
to open a bottle with a corkscrew.”
The first two topics are debatable and much researched, but
I agree with the last point … most of the time. There is a nice vibe to the
ritual of uncorking a bottle of wine, hearing that “plop” sound, and then
extracting the cork from the corkscrew and testing it with a quick sniff.  The ritual of uncorking a lovely bottle of
wine – not to mention the plethora of cool corkscrews now available [I have a
large collection] – cannot be replicated with a twist-off cap. 
However, if wine flows as freely in your household as it
does in mine the convenience of the twist-off cap is often welcome. I don’t
need the uncorking ritual for every bottle I open. I just want that wine
pouring into my glass … quickly.
But what about the wine quality issue. Are corks better for
wine than twist-off caps and is synthetic cork inferior to real cork?  Does it really matter?
Generally speaking, natural corks are used for premium wines that
are meant to age, in some cases 20 years or longer. They have thus far proven
to be the best option, although screw cap research is ongoing and may prove
this wrong. But for the world’s top wine prod

ucers cork is the closure of
choice, and it’s been used for centuries in “old world” wineries. But
overproduction of cork, with less-than-perfect production techniques, led to the
issue of “cork taint.” Corks are also expensive to produce. These factors all
combined sometime in the 1960s to lead to the development of alternative
closures for wine.

Cork taint makes
a wine smell unpleasantly musty or moldy. If a just-opened bottle smells of cardboard,
the wine likely has cork taint. The taint is brought on by the presence of a
substance called trichloroanisole, or TCA. Cork manufacturers have been developing
methods for treating corks to reduce TCA contamination, as well as making
improvements in the processes that lead to TCA contamination in the first place.
In fact, a Code of Good Manufacturing Practice for Cork was developed in the
early 1990s by the European Cork Federation. [It should be noted that TCA can
also be introduced into the wine from barrels and other winery equipment –cork
is not always the culprit.]
Aluminum screw caps (left), synthetic corks (middle), and natural corks (right)

Corks can also allow a slow seepage of oxygen into the
bottle, and oxygen can be both a friend and a foe in winemaking. Too much
oxygen leads to oxidation, a flaw in wine. For example, when a cork dries out
and loses its natural elasticity, it becomes ineffective as a seal and
oxidation can prematurely age the wine. Oxidized wine has lost its fresh,
fruity aromas and becomes flat smelling. Worst case scenario, the oxygen
converts the wine’s natural (and desirable) acid into acetic acid, which is
basically vinegar. On the flip side of this – and this is what is being intensely
studied by the experts – a  little oxygen
can be good for the long ageing process, allowing the wine to develop complex
flavors and aromas over time.

Synthetic corks are
intended for use on wines that are drunk within a year of bottling. And these
days, that’s many wines, as the trend is to produce wines for consumption while
young. Synthetic corks are not suitable for wines aging longer periods because
they do not provide sufficient protection from oxygen, and some synthetics can
also harm the flavor of the wine over time. But they come in many pretty
colors, and that’s appealing on a marketing level.
Aluminum screw caps
have become fashionable, with both producers of high- and low-end wines.  How can you not love a product that provides
an impermeable seal from air – hence no oxidation – has been shown to preserve
the fruit flavor in wine longer than cork, is less expensive than cork, and
offers wine with one quick twist of the wrist? Screw caps are becoming
increasingly popular for red, white, and rose wines where the fresh fruit
character is important to the winemaker. But some winemakers are worried that
the total oxygen seal, which does not allow the small amount of oxygen seen to
occur with natural corks, will not allow for the proper development of some
The industry continues its long-term studies on corks,
synthetics, and aluminum screw caps, as well as on cork-synthetic hybrids,
glass toppers (expensive), a thing called Zork (a plastic device with a tear
strip that does not require a corkscrew), and other closures. Only time will
tell what the results will be, and there are lovers and haters on all sides of
the discussion.
Until next time, uncork or unscrew and Cheers!