Abstract: In this experiment, we sought to explore the relationship between the change of flavor substances and bacterial community succession during the post-fermentation of red sufu. By using headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS), and reversed-phase high performance liquid chromatography (HPLC) following precolumn derivatization with o-phthalaldehyde (OPA), we detected the contents of volatile flavor compounds and amino acids in the sufu. A total of 50 volatile flavor substances were detected, mainly including 20 ester compounds and 9 alcohols. The main flavor substances identified by odor activity value (OAV) analysis were phenyl ethanol, 1-octene-3-alcohol, ethyl acetate, etc. The types and contents of most flavor compounds such as esters, terpenes and furans were increased with fermentation time, while those of alkanes and esters were not changed significantly. The total content of free amino acids (FAA) was similarly increased with fermentation time. The bacterial community was analyzed by high-throughput sequencing, and it was found that the dominant bacteria were Bacillus, Enterobacter, Acinetobacter, Tetragenococcus, etc. The diversity of bacterial community was increased significantly during fermentation. The abundance of Bacillus was decreased significantly, while the abundances of Lactococcus and Tetragenococcus were increased over the entire fermentation period. The abundance of Enterobacter was increased significantly in the early-mid part of the period and then decreased in the mid-late part. Pearson correlation analysis showed that the production of amino acids in the post-fermentation period of red sufu was positively correlated with Enterobacter, while the production of most aroma compounds was negatively correlated with Enterobacter. Bacillus was positively correlated with a variety of ester aroma compounds. Other strains, such as Lactococcus and Acinetobacter, also provided good flavor during the post-fermentation period.

Key words: red sufu; volatile flavor substances; free amino acids; bacterial community; high throughput sequencing