Article by The Indian Wine Academy

An article by an Aussie MW Alison Eisermann-Ctercteko who did research for her MW dissertation claiming that the total screwcap damage levels at 8.2% were greater than cork taint, thus suggesting serious implications for producers, retailers and consumers, has raised a voice of disagreement from various quarters suggesting that the study was flawed

The Dissertation topic might have earned the Australian Alison Eisermann-Ctercteko her Master of Wine certification for ingenuity and daring to be a contrarian in the growing market for Screwcap closures especially Down Under, but many of her assumptions to come to such a high level of defects seem to be flawed. Reported in the Australian trade magazine Wine and Viticulture Journal in its September-October issue, the study suggested that there were factors during bottle filling to reaching the consumer through the retail stores that caused various defects in the wine and were far more serious than the cork taint.

The article was also carried by Jamie Goode, the well respected English journalist who also writes for Decanter and runs his own Blog The original report might not have been noticed much but his Blog caused quite a stir among his followers, because the study had indicated that 26% of all caps showed some physical damage, and over 8% of screw-capped wines showed sufficient cap damage to cause significant chemical changes.

Eisermann-Ctercteko had examined over 10,000 bottles for damage. She then bought 600 bottles of a 2012 Sauvignon Blanc for chemical analysis. She conducted a formal trial of 444 bottles with increasing cap damage, which she classified from A-D in ascending severity. There was also a class E which was where the cap was undamaged but had been applied incorrectly.

There were 84 controls and 72 wines in each category, with the damage inflicted artificially on each damaged bottle to the appropriate level. The wines were stored for 10 weeks, and a number examined chemically at two week intervals, with the largest sample being at the end of the 10 weeks when the remaining bottles were tested. The chemical analysis was for absorbance at 420 nm (looking at the browning of colour, an indicator of oxidation) and free and total sulphur dioxide (SO2 being a marker of oxidation). Sensory analysis was also carried out.

In his initial Blog, Jamie had said, ‘the IMW keeps dissertations to themselves, so there’s no way for us to see them-one of the flaws of the dissertation section of the MW exam. Without access to data, and also taking into consideration this wasn’t a peer reviewed study, I can’t be sure the methodology is correct or exactly what the data show. But it’s an interesting study by the sounds of it.’

Interesting it was! With the IMW agreeing to send him a copy of the dissertation as it was not of commercial secrecy importance and  so he could see the data, and after having spent some time examining it, he concedes in another Blog later that the figure of 8.2% is misleading. ‘From Alison’s data on the incidence of level of damage found in retail stores, that figure of 8.2% now becomes 0.06% , a much less alarming figure’, than the 3.5% he reckons is the spoilage of wine through cork taint.

Meanwhile, the cork industry has come to accept that the screw-caps will co-exist with cork. Although the industry has been pouring millions of euros during the last decade and a half, with the Portuguese producer Amorim claiming to have brought down the level of cork taint to around 1%, there has not been a big rush of the screw-cap users switching back to the cork.

‘The increased use of screwcap closures over the past decade has led to an overall improvement in wine quality, retention of aromatics and longevity. In particular, there has been the reduction in cork-related problems of TCA cork taint and random bottle oxidation,’ is how the article relating to her dissertation begins.

‘Over the past few years, increasing numbers of bottles with imperfect application and physical damage to closures have been noted particularly in retail outlets, wine assessments and in certain store display types. Upon tasting these wines, it is often evident that the wine quality has been affected; namely oxidative characters. The wine can appear dull and flat, lacking aromatic character and showing premature development. This prompted research to be undertaken to identify the level of screwcap damage that will lead to changes in wine chemistry, measure the incidence of screwcap damage in the market and to determine where and how the damage is occurring. Surveys of 22 retail outlets, mostly in metropolitan Sydney with small to large warehouses were made with 10,000 bottles, plus 1500 in the UK, visually assessed.’

India, where the retail sector is not as sophisticated, hasn’t seen such an alarming rate as concluded by the dissertation. In fact, the bigger problem has been the manufacturing defect in the screwcaps – at times, one needs to have acrobatic qualities to open the screwcap (in all fairness the problem is no worse than opening a cork which is so tight that is needs a lot of dexterity and patience to uncork some bottles). But the study is likely to create more than a passing academic interest for the producers, most of whom use screw-caps for white wines and the low end reds. The top end reds are invariably still using the corks of varying quality.

The title of Alison’s successful dissertation was ‘Monitoring the incidence and nature of screwcap closure damage, its effect on aromatic wine quality and the implications for storage and handling: an investigation of Sauvignon Blanc.’ She became the 19th Master of Wine from Australia in June this year.

Subhash Arora