The Australian Wine Research Institute

The Australian Wine Research Institute is pleased to announce the first publication of results arising from the AWRI trial of the technical performance of various wine bottle closures, in the June 2001 issue of the Australian Journal of Grape and Wine Research (AJGWR), which has been distributed today. This report is considered to be of major importance to the Australian wine industry and to closure manufacturers and suppliers.

• A Semillon wine was bottled under controlled conditions on 26^th May 1999, using 14 different closures: a screw-cap type, two grades of conventional cork, two types of ‘technical’ cork (natural cork with a synthetic component), and nine closures manufactured from synthetic polymer material. During the 20 months following bottling, the physical aspects of the closures’ performance, and the chemical and sensory changes in wine sealed with each of the closures has been assessed periodically. The study is ongoing, with sufficient wine bottled for up to 10 years of testing.

• It is apparent from the results to date that many of the closures trialled are suited to short term (approximately 6 to 12 months) storage of wines, but for longer time periods there is doubt over particular closures’ abilities to act as an adequate seal, with consequent effects on sulfur dioxide (SO₂) levels in the wine, browning, and on oxidised aroma. No one closure tested in this study could be considered entirely suitable by all criteria assessed, for the long-term storage of wine.

• Wine sealed with the screw cap retained the greatest concentration of SO₂ and ascorbic acid, and had the slowest rate of browning. For other closures, the trend of SO₂ loss relative to wine sealed with the screw cap was apparent from an early stage, and was most evident in the group of synthetic closures, intermediate in the conventional corks, and least evident with the technical corks. The concentration of SO₂ was a strong predictor of future browning in the wine.

• After 12 months of storage, wine in bottles sealed with the closures showing the lowest SO₂ concentration were rated as sufficiently high in oxidised aroma to consider them as markedly lower in quality. For closures with intermediate SO₂ concentration at this time, there were diminished ratings in the fruit sensory attributes, and increased developed aroma. Whilst TCA taint was a noticeable problem for some cork and technical corks, any plastic-type taint appeared not to be a problem with most synthetic closures, with one notable exception. After 18 months of storage a rubber-like aroma had developed in wine sealed with the screw cap closure.

• The closures differed widely in regard to physical characteristics, and in general synthetic corks appeared least ‘consumer-friendly’ in terms of the forces and energy required to extract them from the bottles and from a corkscrew, and in the ease of manual reinsertion into the bottleneck.

• For a range of performance criteria, the technical corks were found to exhibit less variability than synthetic closures which in turn tended to be less variable than the natural cork closures.

Copies of the publication can be obtained by contacting Ms Val Rechner at the AJGWR, PO Box 197 Glen Osmond, SA, 5064. tel:08 8303 6607, fax: 08 8303 6803 asvo@waite.adelaide.edu.au

Other enquiries should be directed to:

Winemaker and Manager – Industry Services, and project leader
Peter Godden
tel: 08 83 03 66 00
Peter.Godden@awri.com.au

Director of the Institute
Peter Høj
tel: 08 83 03 66 11

Quality Liaison Manager
Mark Gishen
Mark.Gishen@awri.com.au

The Australian Wine Research Institute has become aware that reports have appeared in various media, including the Adelaide Advertiser and various wine industry websites, that The Australian Wine Research Institute has endorsed NuKorc’s wine bottle closure.

An article appeared in the Adelaide Advertiser of 20 January 2001, an extract of which stated:

“Mr Dolling said NuKorc’s edge was that its closures were extruded from continuous lengths of polyethylene and cut to fit the bottle rather than moulded. Scientists at the Australian Wine Research Institute claim NuKorc’s product is the ‘most technically correct synthetic closure available’. The synthetic corks had an even cell structure compared to moulded corks and held to the bottle wall better, keeping oxygen out, Mr Dolling said”.

NuKorc, through Mr Ben Atkins, has indicated that it would never make such a statement, and has written to the Adelaide Advertiser denying that Mr Dolling made the statement regarding The Australian Wine Research Institute.

On “News and Views” at http://www.decanter.com NuKorc is reported as saying:

“their extruded stopper (it is made in a long ‘sausage’ and then cut up) is denser than rival Supremecorq, which is moulded. Backed by detailed scientific analysis from the Australian Wine Research Institute, they claim it is ‘the most technically correct synthetic closure available’ “

Press releases on the Wine Pros and Vintage Cellars Australia websites, report Mr Dolling of NuKorc at a London tasting as saying:

“We believe that NuKorc is the most technically correct closure available because its microcell structure is more even and dense than our moulded competitors”.

The report goes on to say:

“The wines presented were backed by detailed analysis from the Australian Wine Research Institute.”

The Australian Wine Research Institute has never made any claim to the effect that NuKorc’s product is the most technically correct synthetic closure available, and is most concerned at the appearance of incorrect media reports that it has done so. As an independent industry body The Australian Wine Research Institute considers it to be of the greatest importance that its reputation not be compromised by having incorrect assertions of its support for commercial products appear in the press. The Australian Wine Research Institute hopes that this press release will be sufficient to prevent any further such reports being published, and at the same time rectify any wrong impressions that the media reports may have created.

MR PETER GODDEN
Winemaker and Manager Industry Services

PROF. PETER HØJ
Director
The Australian Wine Research Institute

Telephone: 08 83 03 66 00; fax: 08 83 03 66 01; email: Peter.Godden@awri.com.au and Peter.Hoj@awri.com.au