Unexpected impact of 2-methylisoborneol as off-odour substance in aged wines

- Odorants in long-aged wines affected by musty-mouldy aroma were compared by AEDA.
- Musty-mouldy smell was related to intensity of 2-methylisoborneol (2-MIB).
- This was unexpected as previous studies reported 2-MIB instability in wine.
- Model degradation studies, however, demonstrated decelerating decrease of 2-MIB.

Four Pinot noir wines from Burgundy were investigated by gas chromatography-olfactometry, with regard to the presence of earthy-smelling compounds. 2-Methylisoborneol (2-MIB) was detected in two of these wines, although the samples were seven years old, contradicting previous reports that this substance is unstable in wine and must. In order to investigate this seemingly paradoxical situation, 2-MIB stability was reinvestigated in wine and in model solution starting with an elevated initial concentration. Although 2-MIB concentration greatly decreased during the 90 days of storage, the final concentration measured in both media was well above the odour threshold of the substance. Based on the observation of a decelerating decrease of 2-MIB with time, it was concluded that this substance can still be detected in wine and can induce, in this case, an earthy off-odour on condition that the start concentration is high enough.