Abstract: In order to study the effect of enzymatic hydrolysis of soymilk on the microstructure and physicochemical properties of dried tofu, changes in the surface hydrophobicity, protein thiol content and disulfide bond content of soymilk were evaluated after being hydrolyzed by flavourzyme and texture properties, microstructure, water state, water-holding capacity, in vitro digestibility and sensory characteristics of dried tofu were determined. The results showed that compared with untreated control, the surface hydrophobicity and disulfide bond content of soymilk hydrolyzed for 30 min increased by 1 904.5 and 0.18 μmol/g, respectively. The sensory quality of dried tofu was significantly improved at first and then deteriorated with increasing hydrolysis time, and the highest sensory score was reached at 30 min. Compared with the control, the microstructure of dried tofu made from hydrolyzed soymilk was tighter and more uniform, the hardness, springiness, chewiness, cohesiveness and resilience were also improved. The water-holding capacity and in vitro digestion rate were increased by 9.29% and 9.00%, respectively, and the water loss rate was reduced by 0.2% when the enzymatic hydrolysis time was 30 min. Enzymatic hydrolysis of soymilk could the increase its protein thiol content and surface hydrophobicity, and then affect the structural compactness and sensory characteristics of dried tofu. This study provides a preliminary theoretical basis for quality improvement of dried tofu and for the application of enzymatic hydrolysis in soybean products.

Key words: dried tofu, enzymatic hydrolysis, texture characteristics, microstructure, water state, water holding capacity, in vitro digestibility