Comparison of Sulfide Compounds in Wines Finished with
Natural Cork and Screwcaps
Internal CQC survey - February 2007

Summary : Presents results from a small market survey of comercially distributed Sauvignon Blanc wines from Australia and New Zealand. Samples, comprised of wines finished with natural cork or screwcaps, were analyzed for a range of sulfide compounds associated with wine. This was an uncontrolled survey that cannot furnish formal conclusions, but does indicate that the screwcap wines in the sample had very high levels of dimethylsulfides (DMS). Comparison to similar cork-finished wines showed that DMS levels three times greater in screwcap finished wines.

Characteristics of Oxygen Permeability in Wine Closures
Presented by Paulo Lopes PhD, University of Bordeaux -
APCOR Cork Seminar - June 2006 - St. Helena CA

Summary : This study incorporates a colorimetric method for detecting oxidation, allowing more precise measurements of oxygen ingress than most previous work. Dr. Lopes demonstrates the comparative differences between wine closures in allowing oxygen ingress. His findings conclude that (1) Synthetics were too permeable – and caused premature aging (2) Screwcaps were not permeable enough – and did not allow proper aging. The implication was that natural cork offered a perfect balance.

Summary : Dr. Limmer’s experience as a New Zealand winemaker gives him extensive familiarity with modern screwcap closures. His presentation explains the source of reduced aromas that can be encountered when a lack of oxygen is present in wine. Dr. Limmer is convinced that many wines suffer loss of fruit and present a characteristic "dullness" when this condition occurs.

AWRI Closure Comparison at 18 Months
Excerpts from the AWRI Closure Report
as seen in Australian Journal of Grape and Wine Research 7.64-05.2001

Summary : This presentation is a summary of data presented in graphical form from the oft-quoted AWRI Report on Wine Closures. Much of the data has been selectively reported by various manufacturers of alternative closures. In this display, all of the sensory results are reported together. At the 18-month point there appear to be several conclusions:

1. No single closure demonstrated completely satisfactory results.
2. Synthetic closures had significant issues related to off–aromas and oxidation.
3. Screw caps had better results regarding oxidation but showed evidence of “glue–like” and “reduced” off–aromas.
4. Natural Cork had good marks regarding fruit retention and oxidation. Off–aroma issues were primarily related to TCA.