Analysis of volatile substances in Stropharia rugosoannulata Farlow cultivated under forest canopy with four different culture substrates by electronic nose and GC-IMS

This study examined the volatile organic compounds (VOCs) in Stropharia rugosoannulata Farlow that were cultivated on four substrates formulated with agricultural and forestry wastes. The VOCs were analyzed by an electronic nose (E-nose), gas chromatography-ion mobility spectroscopy (GC-IMS), principal component analysis (PCA), and an orthogonal partial least squares discriminant analysis (OPLS-DA). A4(40% sawdust, 30% camellia shells, 20% rice husk, 8% bran, and 2% lime) was the most effective overall at determining the quality of flavor. The E-nose showed that there were similar profiles of aromas for A2(100% Eleusine coracana (L.) Gaertn straw) and A3(70% bamboo chips, 20% rice husk, 8% bran, and 2% lime). A total of 91 VOCs, including 82 known compounds, such as formaldehyde, alcohols, esters, and ketones, and 9 unknown compounds, were detected in each sample by GC-IMS. The relative contents of formaldehyde, ketones, alcohols, and esters in the samples was more than 80%. Among the 29 VOCs with variable importance in projection (VIP) values > 1 and P < 0.05, formaldehyde, heptagonal(dimer), 2-methyl-E-2-butenal-M”, 3-methyl-2-butenal-M(dimer), 1-octen-3-ol, butyl acetate(dimer), ethyl 3-methylbutanoate, and 2-pentylfuran were the markers that distinguished the volatiles in S. rugosoannulata cultivated with different groups of raw substrate materials.