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The purpose of the present study was to evaluate the volatile profile of Kedong sufu, which is a typical bacteria‐fermented soybean product in China, using solid phase microextraction coupled to gas chromatography and mass spectrometry and to reveal the evolution and diversity of flavor substances for this specialty. A total of 75 compounds were identified, including 35 esters, 4 alcohols, 4 phenols, 4 aldehydes, 7 acids, 10 ketones, and 11 other compounds from sufu samples during ripening. Some volatile compounds increased with ripening time, especially hexadecenoic acid ethyl ester, methoxy acetic acid pentyl ester, benzene propanoic acid ethyl ester, ethyl 9‐hexadecenoate, ethyl oleate, ethanol, 3‐methyl‐1‐butanol, 5‐methoxy‐1‐pentanol, and eugenol; these compounds enriched the flavors and provided the typical savory taste of Kedong sufu. Practical Application This research elucidated the formation of flavor substances in sufu. For traditional fermented foods, this study provides a scientific basis for promoting the generation of typical flavor substances and for the precise determination of maturity time.

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Elucidating the metabolite profiles during the growth of Streptococcus thermophilus is beneficial for understanding its growth characteristics. The changes in the intracellular and extracellular concentrations of carbohydrates, nucleotides, amino sugars, nucleoside sugars, fatty acids, and amino acids, as well as their metabolites over time, were investigated by metabolomics technology. Most metabolites of nucleotides were highly accumulated in the intracellular environment after the mid-exponential phase. Increases in the intracellular unsaturated fatty acids and N-acetyl-glucosamine and N-acetyl-muramoate recycling provided potential evidence that cell envelope remodeling occurred after the mid-exponential phase. At the later fermentation stages, potentially functional metabolite produced by glycine was highly accumulated in the intracellular environment. Additionally, potential toxic metabolites produced by phenylalanine and tyrosine could not be excreted into the extracellular environment in a timely basis. The accumulation of large amounts of these metabolites might be the primary cause of the overconsumption of amino acids and influence the growth of S. thermophilus.

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