Objective To compare the composition and content differences of volatile components in Liushenqu (六神曲, Massa Medicata Fermentata, MMF) samples with different fermentation times, clarify the material basis of the unique aroma of MMF, and identify the key components that give it its main characteristic aroma. Methods Taking MMF fermented for different durations as the research object, and electronic nose was used to characterize its overall odor profile, and gas chromatography-mass spectrometry (GC-MS) was combined to analyze the specific volatile components. Chemometrics was applied to screen the differential components at different fermentation stages, and the relative odor activity value (ROAV) was used to reveal the odor differences of MMF and the material basis for its odor formation. Results Based on the detection results of the W5S, W1W, and W2W sensors of the electronic nose, the fermentation process of MMF was clearly divided into three stages: T1—T4 (initial fermentation), T5—T8 (middle fermentation), and T9—T12 (late fermentation). A total of 120 volatile components were identified by GC-MS. Principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) confirmed that there were significant differences in the volatile components of MMF at different fermentation times. A total of 49 differential components were screened out according to the criteria of variable importance in projection (VIP) > 1 and P < 0.05. Combined with the relative odor activity value method, 5-hydroxymethylfurfural was identified as the component contributing the most to the characteristic aroma of the main body. 2-Hexene, pentyl (9E)-octadec-9-enoate, 3,5-dihydroxy-1-nonadecylbenzene, and methyl 2-methoxy-5-hexadecenoate played important modifying roles in the characteristic aroma. Conclusion The differences in volatile components during the fermentation of MMF can be effectively analyzed by electronic nose, GC-MS, combined with the relative odor activity value method, which provides a scientific basis for the identification and quality evaluation of MMF.

Massa Medicata Fermentata  /  electronic nose  /  GC-MS  /  relative odor activity value  /  aroma components  /  fermentation  /  volatile components  /  chemometrics  /  5-hydroxymethylfurfural  /  2-hexene  /  pentyl (9E)-octadec-9-enoate  /  3,5-dihydroxy-1-nonadecylbenzene  /  methyl 2-methoxy-5-hexadecenoate