Screwcap vs Cork- Australian Wine

Did u know Aussie develop the technology back in the 70s but it wasn't really adopted until the 2000s. The Oz wine industry basically had enough of wines being destroyed by cork!
Ralph Kyte-Powell posted this photo on Facebook which I found really interesting.
His comments were- 'Just prepared a story for the next edition of Jame Halliday's Wine Companion magazine on the same bottle-aged wines under both cork and screw cap. The wines in these glasses are both Penfolds Yattarna Chardonnay 2002. Guess which one is the cork-sealed bottle.'
' Correct. The one on the left. A picture is worth a thousand words. Putting finishing touches to the results of the tasting of 33 assorted wines from various vintages between 1997 and 2006. The story will examine relative ageing as well as faults etc. To be published in Wine Companion and will let you know exact publication date soon.'
I shared this photo on my timeline and the questions came rolling on in and it only seemed natural to do a Blog Post on it.

First a bit of history.
Screw caps were first developed in the 70's in Australia.
The Stelcap in 1970. The original Stelcap used a cork layer and paper, and then after that an expanded polyethylene layer. A cork was used under these caps.
Stelvin® was commercially introduced into Australia by ACI in 1976. The difference between this and the Stelcap being the wadding material which, in the case of Stelvin®, consisted of a layer of tin adhered to a backing material, with the tin being covered by a layer of PVDC – this PVDC was the wine contact layer. The original design was French, produced by Le Bouchage Mechanique (LBM).
Yalumba , Hardys, McWilliams, Penfolds, Seppelt, Brown Bros & Tahbilk were involved in developing and proving up the concept from about 1973, first using it commercially in 1976.

Unfortunately, while the wine industry was excited about the screw-cap, wine consumers were less so, seeing the metal cap as an indication of a lower quality product. As a result many of these wines that had been sealed under screw-cap reverted back to cork.
In 1882 Linda remembers when Ian worked at Houghton's in the Swan Valley. Then winemaker Jon Reynolds brought a screw cap wine to dinner and showed them the new developments in the wine industry. Houghton's were trailing screw caps with their rose and a white wine ( mum can't remember which?).
At the time, the wine industry was concerned that the screw cap made the wine look cheap and that while the technology of the screw cap was developed, the winemaking side hadn't. For example, if screw cap didn't breathe how would the wine aged? And the other big difference is a cork leaves an ullaged gap of approx. 10mm a screw cap wine leaves an ullaged gap of approx. 35mm. How would the extra 25mm of ullaged effect the wine? (I will answers these question further down in the post.)
By 2000 screw caps were back and these questions were addressed but the main reason the wine industry uses Screw-cap is that it eliminates the possibility of wine taint from cork
Cork taint is a broad term referring to a wine fault characterized by a set of undesirable smells or tastes found in a bottle of wine, especially spoilage that can only be detected after bottling, aging and opening.
It is said that 1 out of ten wine exhibit cork taint and this proved frustrating to wineries who received complaints from consumers. So if you made 100 bottles of wine you potentially could receive 10 negative feedbacks. Marketing tells us for every bad experience that person tells ten people and so on. The larger the quantities the more complains. At the end of the day the development of screw caps was to solve the quality of wine.
The chief cause of cork taint is the presence of ( for the science nerds out there!) 2,4,6-trichloroanisole (TCA), and/or 2,4,6-tribromoanisole (TBA), in the wine, which in many cases will have been transferred from the cork, but which also can have been transferred through the cork rather than from it. Corked wine containing TCA has a characteristic odour, described as resembling a mouldy newspaper, wet dog, hessian bag, damp cloth, or damp basement. In almost all cases of corked wine the wine's original fruit driven aromas are reduced significantly, and a very tainted wine is quite unpalatable, although harmless.
I have a winemaker friend who does a great party trick of putting slightly corked wine into a decanter with crumble up cling wrap and it reduces the cork taint! But it still is a dull wine and I would recommend opening up another bottle!

How do screw caps affect the ageing of the wine? Compared to cork?
The brown colour of the left is the effect of air on the wine! Plus I bet the sulphur levels are different (but that's me getting technical). Basically the cork is a natural product that 'breathes' which allows the wine to breath hence the development in colour. But the real concern to the wine industry with corks was that 1 out of 10 wines were corked (corked- making wine undrinkable with Hessian bag favours)
Aging wine in screw caps is still a learning curve for all because the technology is still new. But you can see from this example it certainly retains the colour. You also don't need to lay wine down any more!

So why don't you need to lay wine down that is in screw cap?
Basically you need to lay wine down in cork to keep the cork moist and stop it from drying out. If you leave a cork wine standing up the cork will shrink letting air into the wine and spoiling it. Even lying down the cork still "breathes" but the cork will not dry out. Screw cap in contrast does not let any air into the bottle. So with screw caps you don't need to bother however I must admit all my wine is stored lying down but that's more to do with the design of wine rack and wine fridges than science.

So being completely sealed off doesn't affect the maturing of the wine? Does a screw cap allow you to cellar a wine for longer?
Good question! Not allowing the wine to breath is a debate within the wine industry (but a complicated one) but wine can still age in screw cap. Just differently. The wine industry is hoping that we will be able to age wine in screw cap longer than in cork!
Screw caps prevent the wine faults of oxidation and of cork taint, and are easier to open, although there are concerns about long-term aging (aging for decades). Some argue that the slow ingress of oxygen plays a vital role in aging a wine, while others argue that this amount is almost zero in a sound cork and that any admitted oxygen is harmful.
At this stage it is widely believed that screw caps are perfectly fine for aging wine.
Maturing wine is effected also by sulphur levels decreasing in wine hence the colour!
Aging wine is complicated in itself. There are many factors that age a wine. While wine is a perishable product and capable of deteriorating there are many factors that affect aging including grape variety, vintage, viticultural practices, wine region and winemaking style.
Then there are things like pH, tannins, and acidity. Did you know tannins in reds and acidity in whites act as a preservative and are key elements with aging wine? Look at Riesling which is high in acid and ages for 20+ years or Cab Sauvignon which are high in tannins and again age for 20+ years.
Plus the ratio of sugars, acids and phenolic to water is a key determination of how well a wine can age. The less water in the grapes prior to harvest, the more likely the resulting wine will have some aging potential. This is where Grape variety, climate, vintage and viticultural practice come into play here. Grape varieties with thicker skins, from a dry growing season where little irrigation was used and yields were kept low will have less water and a higher ratio of sugar, acids and phenolic. Sound familiar? Our dry grown vineyard is a great asset to aging our wine!

You said the wine sealed by the cork would probably have more sulphur in it. Is that used as a preservative?
No wine with cork less sulphur. And when it ages because the cork allows oxygen in the sulphur in cork wines is absorb quicker by oxygen. Hence the colour. Yes sulphur is a preservative but wine has less sulphur in it than commercial fruit juice! Before people go all anti sulphur! That's why the wine has a yellow colour and lacks taste due to spoilage which would have been prevented by appropriate sulphur levels.
Also this is where that question of an extra 25mm of Ullaged comes in. To account for that extra Ullaged we put extra sulphur in to protect the wine from spoilage. But it is small amount really. And extra 10ppm (parts per million). I talk about sulphur in wine in another post if you want to know more about wine and sulphur.

So which wine do you prefer to drink wine in cork or screw cap??
I drink wine with cork & screw cap but I am quite forgiving. If the wine is undrinkable I simply pour it down the sink and grab another bottle. Screw caps are about quality assurance!
I hope this answers a few questions on the topic- I could have written pages on it as one questions leads to another and so on. I guess at the end of the day winemaking is not an exact science especially with me- I am a very intuitive winemaker.

Ralph Kyte-Powell My story about the cork v screwcap tasting of 32 wines will be published in Wine Companion on 28 April. Results were very interesting. By the way, the screwcapped Penfolds Yattarna pictured above was far superior - the cork sealed wine was dead and gone.