Characterization and Comparison of Key Aroma Compounds in Traditional and Rapid Yongchuan Douchi by Molecular Sensory Science

Yongchuan douchi is a famous soybean product that is widely used as a condiment in China due to its attractive aroma and can be categorized into traditional and rapid Yongchuan douchi (TYD and RYD). However, the key aroma compounds in TYD and RYD and their differences remain poorly understood. In the present study, the key aroma compounds in TYD and RYD were characterized and compared by a molecular sensory approach. The results obtained by two-dimensional comprehensive gas chromatography–olfactometry−mass spectrometry (GC × GC−O−MS) demonstrated that a total of 125 volatiles and 71 aroma-active compounds were identified. Moreover, 36 aroma-active compounds with odor activity values (OAVs) ≥ 1 and flavor dilution (FD) ≥ 16 were screened and quantified by an external standard method. The recombination and omission experiments revealed that TYD and RYD contained 18 and 13 key aroma compounds, respectively. TYD and RYD contained 10 identical compounds, whereas 8 (ethyl 2-methylbutyrate, ethyl 3-methylbutyrate, ethyl isobutyrate, ethyl caproate, ethyl acetate, ethyl benzoate, 4-methyl-2-phenyl-2-pentenal, acetophenone) and 3 (phenylacetaldehyde, 4-ethyl guaiacol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone) were unique to TYD and RYD, respectively. This is the first report of key aroma compounds in TYD and RYD, and it provides insights into improving the aroma of Yongchuan douchi.