Looking for closure: screwcap vs cork

I’m often asked if wine ages the same under screwcap as it does under cork. In various tastings over the years I’ve encountered little difference – assuming we rule obviously cork-tainted and prematurely oxidized bottles out of the discussion.

My feeling is that if there’s any difference at all, it’s that screwcapped wines have a fresher aroma, with the fruit better preserved and more primary, while cork-sealed bottles of the same wine will tend to have a slightly more rounded, mellow palate.

But these preconceptions were certainly not proven consistently true at a tasting of the great New Zealand pinot noir, Ata Rangi (tasting notes), at the winery recently. It was the most comprehensive such tasting I’ve participated in so far.

Winemaker Helen Masters and owners Clive and Phyll Paton lined up 20 masked bottles which gave closure comparisons for six vintages: 2002, 03, 04, 06, 08 and 09. The first three vintages were presented as triangular taste tests.

Tasters were served three glasses, two of which contained the same wine. The repeated wine could be either the cork or screwcap bottle. The question was: is there any difference? If so, what is the difference?

Yes, there are always subtle differences, even between glasses of the very same bottle. This can be due to the glass itself, or simply our imagination. In my view, very subtle differences are not really worth taking too much notice of. Only once did I correctly nominate the odd one out.

In one trio, I preferred a cork-sealed wine; in the other two trios, I preferred a screwcapped wine. But, because I noted small differences between two glasses from the same bottle, I suspect there was little statistical significance in my findings.

For the ‘08s and ‘09s, triangular taste tests were also arranged, but with a difference: each bottle was different. In other words, instead of the replicate wine being poured from the same bottle, it was a different bottle.

With the ‘08s, I preferred one of the two corks, but both the screwcap and one of the corks seemed less evolved than the other. With the ‘09s, the most obvious thing was how outstanding the vintage is. They were all great wines, which I scored in the mid to high 90s.

One of the cork bottles was noticeably more tannic than the other. This is a known feature of cork-sealed wines – that cork can impart extra tannin to the wine.

Finally, the most interesting ‘flight’ was five bottles of the superb ’06 vintage: one each of regular screwcap, natural cork, Diam P1, Diam P10, and screwcap with Saranex* wadding.

Diam composite corks come in several models, with different degrees of air-permeability. P1 is designed to allow the least air into the bottle; P10 is the most oxidative.

The ’06 pinots were all superb wines, but my favourites were the Saranex screwcap and the Diam P1. They seemed the most dense and rich on the palate as well as being youthful and complex. The Diam P10 was my least favoured, most forward developed and slightly drying on the palate.

The regular screwcap seemed slightly block-ish on the palate. The regular cork was tannic, powerful, muscular (cork adding tannin to the wine again?). My order of preference was Diam P1 and Saranex (tied), then cork, then regular screwcap, then Diam P10.

The scary thing is that I scored them 96, 96, 95, 92, 91. This is arguably an exaggerated difference: I was trying extra hard to differentiate the wines, so perhaps I subconsciously made an abnormal effort to spread my scores. Still, on the face of it, a five-point range is a very big difference.

If we really wanted to analyse my findings, it would seem there is no correlation between air-permeability and preference. I liked the low-permeability Diam most, but most-permeable Saranex next. And I liked the higher-permeability Diam least, but the very protective screwcap second-least. It must be said that even the higher permeability Diam is rated by its manufacturer at a fraction the permeability of cork.

So, overall, this tasting probably did not prove that one closure is better than another. How do we define ‘better’ anyway? Not everyone’s taste is identical. And air permeability is not the only consideration when comparing closures.

It is possible some tasters would enjoy Ata Rangi pinot noir under a closure that admits more air when the wine is young. But, what about when it’s older? The same person might prefer the wine after aging under a less-permeable seal.

A final comment: regular cork is the least standardized of these closures, and different corks could have given quite different results. The other closures are all technical, engineered seals, and theoretically more consistent. Just how consistent is for those more qualified than me to say.

And one more thing (this really is the final comment!). The results were close, which means all closures performed well. There were five or six people tasting and we all agreed on that.

Closure permeability, from least permeable to most.

  1. Screwcap, regular Saranex/tin liner
  2. Diam P1
  3. Diam P10
  4. Natural cork
  5. Screwcap, Saranex liner 

NB: Diam’s manufacturer estimates that Diam P1 is 400 times less permeable than a very good natural cork. They estimate a screwcap is 2600 times less permeable than a very good natural cork.

*Saranex: normal screwcaps have a liner composed of both Saranex and tin, and are much less permeable to air than a Saranex-only liner. The latter is usually used on very commercial wines destined for early consumption.

2 thoughts on “Looking for closure: screwcap vs cork”

  1. P D A Calder says:

    Always leave my full name. I do not need to hide behind a comment I make.

  2. P D A Calder says:

    Huon,
    I am a lover of the wonderful sound of a cork being popped from the bottle, that is the only thing going for it.
    With technology we will get that noise one day from a screw cap. But what will be the cost!
    I am a true believer in screw cap. Not so long ago 2 1996 Penfolds Bin 389 came out of the cellar one drunk by all at dinner one used as red wine vinegar, A short time ago the classic occurred.
    Two bottles of 2004 St. Hugo Coonawarra Cab/Sav. one cork and one screw cap. Everyone agreed there is no way you could ever pick the wines being the same make let alone vintage. The screw cap stop supreme. Tasted then drunk 2015.
    Cork is a living product breathes and dies within our life cycle,
    Huon love your direct approach and best regards.
    Peter Calder.

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