Exploration of the Influences of Various Coagulants on Multi-Dimensional Quality Indices During the Pre-Fermentation Stage of Sufu

1. Comparative assessment of three coagulants and recommendations for improving product quality. 2. Comprehensive analysis of physicochemical dynamics during fermentation. 3. Investigation of gelation characteristics and mechanisms during fermentation. 4. Characterization of fatty acids and biogenic amines during fermentation. 5. Characterization of Volatile Flavor Compounds during fermentation. Sufu is prized for its abundant nutrients and cheese-like texture; coagulants play a critical role in gelation during fermented bean curd production, directly affecting texture, quality and physicochemical characteristics. However, the mechanisms underlying the formation of this unique gel structure have not been extensively studied. To investigate this phenomenon, fermented bean curd gels prepared with three different coagulants were analyzed for texture, physicochemical properties and microstructure, and the effects on fatty acids, biogenic amines and flavor were examined. Results indicated a decreasing trend in moisture content during the pre-fermentation period. After 48 h of fermentation, the secondary structure of the gels was dominated by β-sheet conformations, whereas at 96 h β-turns predominated. Scanning electron microscopy revealed a network structure in gels fermented for 48 h and 72 h. Isoamyl acid and hexanoic acid were detected in the glucono-δ-lactone (GDL) and gypsum (GYP) samples; isobutyric acid was detected in the fermented soy whey (FSW) sample, which also contained two unique medium- and long-chain fatty acids, C 8:0 and C 24:0 . Histamine was detected in the FSW sample, but its content declined continuously. The FSW sample contained 13 unique volatile flavor compounds, the GYP sample contained 7 unique volatile compounds, and the GDL sample contained 5 unique volatile compounds. These findings provide valuable insights for improving gel properties and sensory attributes of fermented bean curd.