Determination of Compounds in Eucommia ulmoides Oliv. Bark and Its Fermentation Products via Headspace Gas Chromatography-ion Mobility Spectrometry

The flavor fingerprint of Eucommia ulmoides Oliv. bark (EUb) and its fermentation product were investigated, and volatile compounds were analyzed using headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with partial least squares discrimination analysis (PLS-DA). A total of 71 peaks were identified, of which 51 target compounds were characterized, including alcohols, aldehydes, acids, and esters. The gallery plot contained 186 signal peaks. The results indicate there were significant differences in the volatile constituents of the three edible fungi. Furthermore, EUb also had its own unique composition of volatile components, and after fermentation with different edible fungi, the volatile components in the product changed significantly compared to the raw materials. A PLS-DA was performed based on the signal intensity of the target volatile compounds obtained; the results clearly showed that the samples (edible fungi, EUb, and different fermentation products) in a relatively independent space were well distinguished. This further illustrated that the composition and content of volatile components from EUb were significantly changed by microorganisms through bio-fermentation. Combining the signal intensity of the flavor substance, the difference between the different fermentation products was also clearly observed, and the flavor compound’s fingerprint was established by HS-GC-IMS and PLS-DA methods.