Insights into volatile flavor compound variations and characteristic fingerprints in Longpai soy sauce moromi fermentation via HS-GC-IMS and HS-SPME-GC× GC-ToF-MS

The variations in flavor substances across the different stages of Longpai soy sauce moromi fermentation were analyzed by HS-GC-IMS combined GC × GC-ToF-MS. A total of 374 VOCs were detected from soy sauce, and the highest content of VOCs were alcohols and esters, respectively. In the early stage fermentation, alcohols and aldehydes were the main flavor compounds. The content of esters, pyrazines, furans and S-containing compounds improved with continuous fermenting process. Based on VOCs, the samples could be delineated by clustering and PCA analysis. Of these, 63 VOCs were regarded as the marker VOCs of soy sauce in different fermentation stage. Alcohol, 1-butanol and 3-methyl-2-butenal provided fruity and mellow aroma at the early stage. Caramel-like, malty and sweet aroma could be enhanced by 3-methyl-2(5H)-furanone, 3-methylbutanol, methional and acetyl valeryl in the middle stage. Furthermore, furfuryl alcohol, 2(5H)-furanone, methyl cyclopentenolone, 2-Ethyl-6-methylpyrazine could be served as marker VOCs of matured Longpai soy sauce.