Molecular Rearrangement of Four Typical Grape Free Terpenes in the Wine Environment.

In order to analyze the molecular rearrangement of terpenes in wine during aging, the changes in linalool, α-terpineol, nerol, and geraniol in model wine were investigated in the dark at low temperature for 90 days. Headspace-gas chromatograph-mass spectrometer/olfactometry was used for qualitative and relative quantitation of terpenes. Quantum mechanical calculation was used to analyze the Gibbs free energy. The results showed that nerol was converted into d-limonene, terpinolene, linalool, and α-terpineol. Geraniol was converted into β-ocimene, terpinolene, and linalool. Linalool was converted into terpinolene. The conversion rate of nerol to terpinolene was the highest with 5.94%. α-Terpineol was not converted spontaneously into other terpenes due to its lowest Gibbs free energy, indicating that the cyclization and isomerization could occur spontaneously through an exotherm reaction. However, the dehydroxylation of linalool, nerol, and geraniol required an energy source.