I often find myself in discussions with wine lovers about the benefits of screw caps versus corks. These discussions can last for hours, haha. Now before I start here, I want to explain that like everything in life, both closure methods (and others not mentioned here) have their strengths and weaknesses.
Living in Australia I have learned the benefits of the screw cap, and now defend it strongly. The argument, however, should not be about the type of closure, but rather its effect on the wine.
So what are the effects?
Why are some wines bottled with a cork and others with a screw cap?
Why are some wines bottled with a cork and others with a screw cap?
I work in a winery in Australia, where its two most iconic wines are premium wines where one is under cork and the other under screw cap, so people ask me these types of questions every day - hence why I wanted to write this post.
The first wine is elegant, with floral aromas and a delicate structure. While the wine benefits from the interaction of oxygen with the wine, the tertiary flavours that then develop can quickly overpower the delicate notes in this wine. A screw cap is used to provide a low OTR (Oxygen Transmission Rate), meaning that oxygen can enter and produce these tertiary flavours, but that it happens slowly, and the wine retains it delicacy longer.
The other wine is a stronger, more powerful wine, with primary flavours that aren’t easily overpowered as the wine ages. Allowing a higher OTR allows the tannins to smooth out more quickly, while adding layers of complexity to the wine. If this wine were to be put under screwcap it would need decades for the same results.
As you can see, there are good reasons why each has been put under the closure mechanism that it has. That said, it does not mean that the other option could not have been used – it would simply alter the time needed to effect the same changes to the wine. As they are, both wines have great quality and ageing potential.
Is it true that every wine under cork has ageing potential?
Are screw caps only for cheap wines, and not for wines with ageing potential?
Of course not, many inexpensive wines exist around the world under cork, plus there are different types of cork. There are some types of plastic corks and some agglomerated corks (when cork granules are glued together), that are cheaper and offer limited protection from oxygen ingress, thus are only suitable for wines to be consumed soon after purchase.
Know that there are many premium and super premium wines in Australia which are bottled with screw cap. Research by the Australian Wine Research Institute (AWRI) shows that the screw cap ensures the continuity of wine equal to or better than the cork stopper.
It’s also good to note that different types of screw caps exist. Traditional screw caps made from tin was impermeable to oxygen, which can lead to reductive characteristics. Newer types of screw caps made from “Saran” or “Saranex” allow a small intake of oxygen that increases the OTR and allows the tertiary flavours of aged wines to slowly develop.