Analysis of Differences in Flavor Characteristics among Different Grades of Stir-Fried Pixian Broad Bean Paste by SPME-GC-MS and GC-IMS

In order to identify the differences in flavor among different grades of stir-fried Pixian broad bean paste, solidphase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS), GC-ion mobility spectrometry (GC-IMS), principal component analysis (PCA), orthogonal partial least squares discriminant analysis (OPLS-DA) and odor activity value (OAV) were applied to determine the key flavor compounds. The results showed that SPME-GC-MS identified 88 volatile organic compounds (VOCs), including 15 aldehydes, 11 alcohols, 17 esters, 13 ketones, 5 acids, 5 olefins, 6 alkanes, 7 heterocycles, 2 phenols, 7 ethers and other compounds. Among them, 34 were common to all samples. A total of 57 compounds were identified by GC-IMS, and 16 key flavor compounds with variable importance in the projection (VIP) values > 1 were identified by OPLS-DA. According to their OAV values, ethyl butyrate contributed to the apple-like aroma of super grade Pixian broad bean paste, and isovaleraldehyde contributed to its malty aroma; ethyl isovalerate contributed to the fruity aroma of first grade Pixian broad bean paste, and 3-methylthiopropionaldehyde was responsible for its roasted potato-like and soy sauce-like aroma; ethyl isbutyric acid contributed to the fruity aroma of second grade Pixian broad bean paste, and isovaleraldehyde and isobutyraldehyde were responsible for its malty aroma. Finally, it was determined that the overall aroma characteristics of stir-fried Pixian broad bean paste were fruity, wine-like, malty, sour, herbaceous, cocoa-like, almond-like and soy sauce-like. These results can serve as references for determining the aroma characteristics of stir-fried Pixian bean paste in the future, and provide a basis for the early design of sensory descriptors for quantitative descriptive analysis.