Tasting compares six wines sealed with both corks and screwcaps

Peter Godden, from the Australian Wine Research Institute, outlines the results of two tastings involving identical wines sealed under both screwcap and cork closures.

In November 2018, the AWRI coordinated a tasting of wines that had been sealed with both corks and screwcaps. The tasting formed part of a presentation on the impact of closures on wine development delivered to delegates of a Great Wine Capitals meeting at the National Wine Centre in Adelaide.

The Great Wine Capitals is a network of ten cities, each representing a wine-producing country, with the objective of “achieving excellence in tourism, business services and education within the global alliance of its renowned wine regions”.

The wines sealed under cork and screwcap sourced for the tasting were:

• 2002 Petaluma Riesling (Clare Valley);
• 2002 Shadowfax Chardonnay (Geelong, Adelaide Hills);
• 2006 Curly Flat Pinot Noir (Macedon) (The ‘cork’ version was sealed with Diam technical corks);
• 2010 Wolf Blass Platinum Label Shiraz (Barossa Valley);
• 2004 Lake Breeze Cabernet Sauvignon (Langhorne Creek); and
• 2010 Torbreck ‘Run Rig’ Shiraz Viognier (Barossa Valley).

Despite exhaustive efforts, the author was unable to identify more recent wines that had been sealed with both corks and screwcaps. For each of the wines, six bottes sealed with cork and six bottles sealed with screwcaps were used across two tastings. The wines were tasted blind.

Bottles deemed to be displaying either cork-related taint or oxidation were poured for the audience members to taste, with the opportunity for them to also taste non-tainted and non-oxidised versions of the same wines.

The audiences for the tastings were multinational, with an estimated 30 per cent of said audience being Australians, and approximately 60% from other countries represented in the Great Wine Capitals network.

The remaining, approximate, 10% were mainly people from Asian countries who were attending the event. Most of the audience members were apparently experienced wine professionals representing a broad range of disciplines.

The sensory assessments reported here were informal and made primarily by the author, supported by the opinions of the many experienced wine professionals in the audiences. Audience preferences were gauged by show of hands and the author’s interpretation of audience comments during discussion of each wine.

Incidence of cork-related taint

Four of the 30 bottles sealed with natural cork (13%) exhibited taints likely to be cork-related; three being described as TCA (trichloranisole)-like (two Petaluma, one Lake Breeze) and one exhibiting a strong camphor-like taint (Torbreck).

Amon et al. (1989) reported that in wine, 1-octen-3-one derived from cork, has a camphoraceous odour at a high concentration.

It should be noted that, because of the very small sample size, no inference can be drawn on the true incidence of cork-related taint during the period of 2002 to 2010 when the wines were produced.

None of the six Curly Flat wines sealed with Diam closures displayed a closure-related taint. However, one member of the first audience stated confidently that they thought the wine must be sealed with a Diam closure, because they were able to smell Diam closures in wine.

At that point, the audience had only been told that all the wines were sealed with ‘cork or screwcap’, and Diam had not been mentioned.

Incidence of oxidation in cork-sealed bottles

Two bottles of the Petaluma wine and one bottle each of the Torbreck, Wolf Blass and Lake Breeze wines were considered excessively oxidised and markedly different from the other cork-sealed bottles of those wines.

One of the bottles of Petaluma also displayed TCA taint. One other bottle of the Petaluma wine was also more developed than the remaining three, but not excessively so, displaying a slightly darker colour.

All six bottles of the Shadowfax wine sealed with cork were considered excessively oxidised, with three being described as ‘maderised’.

None of the six Curly Flat wines sealed with Diam closures displayed excessive oxidation.

Incidence of oxidation in screwcap-sealed bottles

No discernible sensory differences were evident within each set of six bottles of the wines sealed with screwcap and no bottles of the screwcap-sealed Petaluma, Curly Flat, Wolf Blass, Lake Breeze or Torbreck wines were considered oxidised.

All six bottles of the Shadowfax Chardonnay, under screwcap, were considered overly developed by many audience members, while others expressed a strong liking for the wine.

The author’s perception was that the condition of the wine was consistent for a Chardonnay of its age, and that it was not oxidised but was ‘drying out’ and was certainly past its optimal drinking age.

Comparison of non-tainted, non-oxidised or overly developed cork-sealed bottles against the screwcap-sealed bottles of the same wines

The three cork-sealed bottles of the Petaluma wine that were neither cork-tainted, excessively oxidised nor showing advanced development were noteworthy for their freshness and similarity to the same wine sealed with screwcap.

Consequently, there was no audience preference for wine sealed with either closure. The remaining 11 bottles of the Lake Breeze wine (five sealed with cork and six sealed with screwcap) were also noteworthy for their freshness and similarity to each other, with the author and both audiences unable to distinguish between them.

The Curly Flat wine sealed with Diam closures had higher perceived colour intensity, less ‘red fruit’ and more ‘dark fruit’ than the screwcap-sealed wine and was marginally preferred by both audiences to the screwcapped bottles.

No discernible sensory differences were evident in the five bottles of the Wolf Blass wine sealed with cork that were not excessively oxidised. However, those bottles were universally seen as marginally different from bottles of the wine sealed with screwcap.

The wine from screw-capped bottles exhibited purpler colour and the wine from cork-sealed bottles was generally seen as slightly more ‘open’, with perhaps more obvious fruit aroma. Almost universally, audience members expressed a strong liking for the wine under both closures, with few people expressing a preference for either the screwcapped or cork-sealed versions, with a 50:50 split between those that did.

The four Torbreck bottles sealed with cork which did not exhibit cork-related taint or excessive oxidation were seen as markedly different from the same wine sealed with screwcap by both audiences and displayed the greatest variability of the eight sets of red wines.

The colour was the most obvious difference, ranging from similar to that of the screwcapped version (noting that the bottle with the camphor-like taint also had a similar bright colour), through to a brown hue.

However, while the bottles sealed with cork exhibited a less bright colour than the wine sealed with screwcap, the perceived colour density was greater, possibly due to reduced SO2 concentration, and the fruit profile was also ‘darker’.

The wine generated extensive discussion and was generally strongly liked but, because of the variability between bottles, it was difficult to gauge audience preference. However, people who strongly favoured the wine sealed with screwcap did outnumber those that displayed acceptance of the substantial degree of oxidative change evident in some cork sealed bottles.

Cork extraction

The corks were extracted using a Durand spiral and tong corkscrew (Figure 1A).

Four out of 30 corks broke on extraction, with all four of the broken corks extracted from bottles of red wine (three Torbreck and one Lake Breeze).

One cork exhibited ‘wine travel’ (Figure 1B) and was extracted from the excessively oxidised bottle of the Wolf Blass wine.

None of the Diam closures in the Curly Flat wine broke on extraction.

Conclusions

The consistency in sensory characters among bottles sealed with screwcap and Diam was much greater than among bottles sealed with cork.

However, it was evident that with bottles not affected by taint or oxidation, the development of four of the wines (Petaluma, Curly Flat, Wolf Blass and Lake Breeze) was similar, regardless of whether the closure was cork, screwcap or Diam.

In both audiences, European delegates volunteered surprise that red wines under screwcaps had aged so similarly to the cork-sealed versions for up to 14 years, apparently having been under the impression that red wines ‘do not age’ under screwcaps.

There was much greater agreement in audience comment and preferences for the white wines compared to the red wines, noting that there were only two white wines. This particularly related to how oxidative change was regarded, with a far greater range in the perception of, and acceptance for, oxidative change being evident for the red wines compared to the white wines.

Recent-vintage wines sealed with both corks and screwcaps could not be found for the tastings, and it is possible that preferences and perceptions might have been different with younger wines.

In addition, the wines that were sourced were noteworthy for their pedigree and it is possible that the outcomes reported might not be representative of a wider range of wines.

However, the quality of the wines did allow the closures to demonstrate their efficacy over the medium to longer term, and it was generally apparent, notwithstanding the tainted or excessively oxidised bottles, that many of the wines were ageing gracefully regardless of the closure.

The best-preserved cork-sealed bottles were the equal of the screw-capped versions, with the converse also being true; in every case, all the screw-capped bottles were the equal of the best cork-sealed bottles.

Acknowledgments

The AWRI thanks Anna Deller-Coombs, Primary Industries and Regions SA (PIRSA), for the invitation to present to the Great Wine Capitals delegates.

The following people are gratefully acknowledged for making wines available for the tasting:

• Andrew Hardy – then of Petaluma;
• Alister Timms and Phil Strachan – Shadowfax;
• Matthew Harrop and Jenifer Kolkka – Curly Flat;
• Chris Hatcher – Wolf Blass;
• Greg and Robyn Follett – Lake Breeze; and
• Ian Hongell and Andrew Tierney – Torbreck.

This work is supported by Australia’s grapegrowers and winemakers though their investment body, Wine Australia, with matching funds from the Australian Government.

The AWRI is a member of the Wine Innovation Cluster in Adelaide, South Australia.

References

Amon, J. M., Vandepeer, J. M., Simpson, R. F. 1989. Compounds responsible for cork taint in wine. Aust. N.Z. Wine Ind. J. 4(1): 62-69

 

This article was originally published in the February 2020 issue of the Australian & New Zealand Grapegrower & Winemaker. To find out more about our monthly magazine, or to subscribe, click here!