Incidence and nature of 'fungal must' taint in wine corks

摘要

The FM taint compound was isolated from batches of contaminated corks and identified by GC/O/MS analysis as 2-methoxy-3,5-dimethylpyrazine (MDMP). This compound has a potent 'mouldy', 'musty' aroma; its aroma threshold in a white wine was shown to be 2.1 ng/L, which is exceedingly low but similar to that of TCA. In the Southcorp Wines assessment of more than 145,000 corks, FM taint was detected in 0.83% of the corks compared with 1.06% for TCA. These results indicated that FM taint was present in the corks at a frequency only marginally less than that of TCA. However, a greater proportion of MDMP may be extracted into the soak wine and exaggerate the importance of this compound. The FM taint and TCA were detected together (and categorised as a distinct group) in about 10% of all corks exhibiting taint in the closure assessments, indicating that MDMP and TCA frequently co-occurred in tainted corks. Reasons have been proposed for co-occurrence of these two compounds and other taint compounds, all of which are microbial metabolites.