The use of a non‐equilibrated solid phase microextraction method to quantitatively determine the off‐notes in mint and other essential oils

The undesirable top notes or off‐notes found in mint, clary sage, and cedarwood oils could be quantitatively determined using a non‐equilibrated solid phase microextraction/gas chromatography/selected ion monitoring/mass spectrometry (SPME/GC/SIM‐MS) technique. Using the low threshold components, dimethyl sulfide, 2‐methylpropanal, 2‐methylbutanal, and 3‐methylbutanal, which are associated with the off‐notes of these oils, their levels could be reproducibly quantitatively determined. The highest level of off‐notes was found in a sample of Scotch spearmint oil where the levels of the four constituents were, dimethyl sulfide (238 µg g−1), 2‐methylpropanal (286 µg g−1), 2‐methylbutanal (1048 µg g−1) and 3‐methylbutanal (1489 µg g−1). These quantitative results in combination with sensory evaluations could provide for a powerful overall assessment of essential oil quality.