Isn’t cork the best for aging wine, since it allows for slow oxygen exchange? As far as I am aware, screw caps do not. ( Correct me if I am wrong, please)
Sorry, David, but you are wrong here . . .
Screw caps do not create an air tight closure - the liner that is inside the cap determines the amount of oxygen that gets in. A tin based liner will allow in a very small amount of oxygen (in the landmark AWRI study, this was similar to the amount of oxygen that the ‘best’ corks allowed in (without the natural variability of natural cork); a polymer based liner allows in more oxygen, but not too much. And there are now a multitude of liners that can be used - similar to the concept of DIAMs and their different ‘numbers’.
Hope that explains it - if not, let me know
Cheers
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This was true for the earlier screw-caps, but as Larry points out, is not true now. There are at least 4 different liners, with different oxygen transmission rates. All of these alternatives have very consistent OT rates, unlike bark cork, which is all over the place.
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Ben,
It’s worth remembering that cans of food or beverages are lined entirely with plastic, I know of no evidence that the food-grade plastics in use now are harmful.
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Lots of concern with plastics in water, etc. I’m not concerned with plastics in screw caps for wine. Better to give up plastic water bottles.
Sure, it’s more the environmental component I meant to refer to, with people not wanting to use plastic in production. But for sure there are folks with concerns about plastic in contact with wine and making decisions accordingly.
Yes, DIAM has a version that uses a plant-based binder and beeswax. I don’t know how much use they are seeing though.
Tin liners are mostly plastic, they just have a tin layer to get that super-low oxygen transmission rate. They use PVDC as the wine contact material and expanded polyethylene as the cushion between the tin layer and the cap.
Although I think a lot of people take that idea as gospel (“slow oxygen transmission through the natural cork is an important positive thing for the maturing of a wine bottle” and/or “using a screw cap means the wine will stay frozen in its youth and not mature”), I don’t think either of those things is really known and proven. I’m basically certain the second thing is not true.
I’ll let @Oliver_McCrum , @larry_schaffer and others with more expertise comment and explain.
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Hi Larry. Appreciate the explanation. I did not know about the special liners in screw caps. I just remember reading about the corks in one of the wine books. Do all the screw caps now come with these liners or just the ones on the bottles made for aging? Like would something like a simple NZ Sauvignon blanc have a lined screw cap?
As far as I know, all screw caps have some kind of liner - even ‘cheap’ wines.
Cheere
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Well another week and two more Sandlands opened. A 2020 Lodi Chenin was as expected, super nice and fresh. And yesterday a 2016 Contra Costa Carignane where the cork was soaked about half way up and the wine is as fresh as can be. The smoky raspberry and silky palate are a true delight.
All to say that the appearance of the cork continues to not correlate to the wine condition. I will add though that these wines have been stored similarly to others I have owned since release and none of them have more than a mm or two of color at the bottom of the cork.