Abstract: This study aimed to investigate the effect of acidification rate on the physicochemical properties of soy protein isolate (SPI) gel induced by glucono-δ-lactone. Soy protein gel samples were prepared at different incubation temperatures. pH, turbidity, gel strength, water holding capacity, frequency-sweeping curves and microstructure were measured to evaluate the changes in the acidification rate of glucono-δ-lactone (GS) and the microstructural properties of soy protein gels. The results showed that with the increase in temperature, the release rate of GDL coagulant became faster, and the rate of decline in the pH of the soy protein isolate gel increased. The protein turbidity increased continuously, indicating that the protein aggregation rate increased. The gel system reached a steady state in a shorter period of time, and incubation temperature was proportional to the acidification rate of the protein gel. As acidification rate increased, the gel strength and rigidity of the soy protein isolate gel increased continuously; the water-holding capacity reached a maximum at 60 ℃. The microstructure results showed that the structure of the soy protein isolate gel maintained at 60 ℃ was more uniform and denser. In summary, acidification rate significantly affected the gel structure of soy protein isolate, and the acidification rate at 60 ℃ resulted in the most dense and uniform gel structure.

Key words: soy protein isolate, gel, incubation temperature, acidification rate, structure