An odour detection threshold determination of all four possible stereoisomers of oak lactone in a white and a red wine

Odour detection thresholds were determined for all four stereoisomers of oak lactone in both red and white wine. The natural cis-isomer was found to have a significantly lower detection threshold than its non-natural enantiomer in both media, and lower than indicated by most other sensory studies. The odour detection threshold for the natural trans-isomer was seven times higher than for the natural cis. Compared to its enantiomer, the natural trans-isomer had a lower detection threshold in the white wine medium, but slightly higher in the red. Duo-trio difference testing between the two trans-isomers added at the same concentration showed no significant difference between the two for both media. Similarly, a duo-trio test conducted between the natural cis-isomer and a mixture of the same amount of natural cis-oak lactone plus an equivalent concentration of the trans-isomer indicated that the latter had little or no influence on the odour impact of the cis-form.