Analysis the Effects of Different Drying Methods on the Volatile Compounds in Morchella esculenta Based on Electronic Nose and Headspace Gas Chromatography-Ion Mobility Spectrometry

In order to investigate the changes in volatile compounds of Morchella esculenta during drying treatments, the volatile compounds of fresh, vaccum freezed-dried, and hot air-dried Morchella esculenta from two different parts (the pileus and stipe) were compared and analyzed by electronic nose combined with headspace gas chromatography-ion mobility spectroscopy (HS-GC-IMS) techniques. The principal component analysis (PCA) of electronic nose data showed that the drying treatment significantly changed the volatile profiles of Morchella esculenta regardless of the sampling parts. The HS-GC-IMS analysis yielded a total of 41 volatile flavor compounds, and abundant amounts of alcohols (40.02%~50.76%), esters (15.82%~25.66%), and aldehydes (18.24%~20.33%) were observed for the fresh sample. Furthermore, the drying treatments resulted in the reduction of alcohols and esters in fresh Morchella esculenta, specifically by 27.39% to 33.51% and 62.14% to 68.51% respectively, while the total contents of ketones and pyrazines increased significantly (P<0.05). Besides, the pileus sample was present with significantly (P<0.05) higher contents of esters and aldehydes than the stipe sample under the same drying treatment. A total of 21 compounds were tentatively identified as key odorants according to relative odor activity value (ROAV) analysis. Among them, 6 compounds were detected from the fresh sample, including 1-octen-3-ol, heptanal, propionaldehyde, 2-octanone, isoamyl acetate, and dimethyl sulfide, which would contribute to mushroom, fruity and ester notes. Three key odorants, namely benzaldehyde, hexanal and 2,3-pentanedione, were only present in the Morchella esculenta sample after drying treatments. This study provides a theoretical basis for the selection of optimal drying methods to prepare dried Morchella esculenta and for the development of deep-processed Morchella esculenta products.