Off-Flavours in Wine and Beverages: Origin, Detection, and Control
-Jerome Lillis, Vinquiry Research Chemist
November 23-25, 2005, Tarrangona, Spain

Under the auspices of DINAMIC Applied Biotechnology Innovation Center, this conference gathered together experts in the origin, detection and control of off-odors in wine and other beverages. Although some other odor producing compounds were discussed, the primary concern was the continuing problem of cork taint, (chloroanisoles) in the wine industry.  The conference also provided an international forum to review the European Union INNOCUOUS Project.  The intent of this project is to stimulate innovation in the process of cork production for elimination of odors responsible for cork taint.

The three plenary speakers, Dr. Mark Sefton, Dr. Christian Butzke and Dr. Pascal Chatonnet, provided historical and practical experience about the cork taint problem.  Dr. Sefton (Australian Wine Research Institute, AWRI) spoke about the impacts of taints on the wine industry, in particular on Australian producers. He also cautioned that as we work to remove TCA, other compounds are becoming more noticeable, for example, 2-methoxy-3,5-dimethylpyrazine (MDMP). MDMP is an extremely potent compound with an unpleasant, musty, moldy aroma with an aroma detection threshold in a white wine of 2.1 ppt.  Dr. Butzke (Purdue University) gave a broad historical overview of the cork taint problem. In his opinion, while there had been some advances, the cork industry still has some fundamental processing problems that contribute to the continued presence of the cork taint issue. The last plenary speaker, Dr. Chatonnet (Excell Laboratory) spoke of the sanitation practices that would minimize the sources of taints.

During the meeting, new cork taints were discussed. Dr. Gary Pickering (Brock University, Canada) presented his work on “Ladybug Taint”.  The compound producing this taint was identified as 2-isopropyl-3-methoxypyrazine.  It has been characterized with an earthy, peanut, and related aroma and flavor component.  Currently, Pickering’s research group is investigating methods of remediation that may remove this compound and help adjust other pyrazine-type compounds that give vegetative flavor components.  Mr. Stephane La Guerche gave a presentation on the effects of microflora expressing earthy and fungal odors. He observed that the production of geosmin in botrytis contaminated samples was dependent on the simultaneous presence of Penicillium expansum.  This study showed that simple models of taint production may not accurately predict the probability of contamination. 

The INNOCUOUS project and others showed work that had been originated to develop novel technologies to detect and cleanse TCA from corks. Some of the procedures to cleanse the cork included Gamma ray irradiation and Ozone based technologies.  Two new detection technologies which were discussed are an enzyme-linked immunosorbent assay (ELISA) and a reagentless electrochemical immuno-sensor.  The two techniques are still not sensitive enough (the best limit of detection was 2 ppb) but they have the possibility of being incorporated in an ELISA type (96 well plate) rapid throughput screening method. This type of analysis would lower the cost and the technology level for analysis, allowing for incorporation into TCA control during cork processing. 

The reoccurring theme throughout the conference was the relationship between chloroanisoles and chlorophenols. During a round table discussion, it was pointed out that since the chloroanisoles were derived from chlorophenols, it is necessary to determine how this conversion is taking place. Cork oak forest management and proper handling of the cork bark are integral to reducing the problem.  

The take-home message was that improvements have been made, however TCA still is at an unacceptable level in corks. Maintenance of good sanitation procedures and quality assurance checks are critical to avoid TCA contamination.