Analysis of Volatile Components in Laoxianghuang During Fermentation by Electronic Nose, GC-MS and GC-IMS

The changes of volatile components in Laoxianghuang during fermentation were analyzed by electronic nose, gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS), and their contribution to odor was evaluated by relative odor activity value (ROAV). The results showed that, E-nose PCA could effectively distinguish the samples at different fermentation time, and the volatile components began to change significantly after 6 months of fermentation. GC-MS identified 46 volatile compounds, including terpenes, alcohols, aldehydes, phenols, esters, ethers, heterocyclic compounds and others. α-pinene, β-pinene, myrcene, terpinene, limonene, isoterpinene, 1-caryophyllene, valencia limonene, linalool, α-terpinene, furfural, maltol, anethol and 2, 4-dimethylstyrene were 14 common components at high and relatively stable contents during fermentation. 38 known volatile components were detected by GC-IMS, including terpenes, alcohols, aldehydes, esters, ketones, phenol, acids, heterocycles and other volatile components. The results of ROAV showed that the main aroma of Laoxianghuang were citrus, woody, herbal and burnt sweet, and citronellal, nonanal, isoterpinene, trans-β-ocimene and limonene contributed the most to the flavor of Laoxianghuang. Fermentation could enrich the volatile components of Laoxianghuang and the volatile components such as trans nerolidol, heptanal, furfural, hexanal, isovaleraldehyde, 3-hydroxy-2-butanone, 2-ethyl furan, furan methanol and 2-acetylfuran were produced during fermentation.