Effects of different rehydration methods on the rehydration quality of textured fibril soy protein and construction of kinetic model

Textured fibril soy protein (TFSP) is one of the most important high-density plant proteins with a fiber structure similar to meat using screw extrusion. It is often used to process simulated meat products after rehydration treatment. In this study, the rehydration dynamics model was constructed to predict the rehydration process using different ultrasonic power and NaHCO₃ concentration at 40℃. A systematic investigation was implemented to explore the effects of different rehydration modes on the physical and chemical properties, as well as the microstructure of TFSP. The rehydration quality of TFSP was evaluated to compare with the control group, Results showed that the final moisture content increased by 27.14 %, when TFSP rehydrates to 120 min, whereas, the rehydration time was shortened by 20 min in the 500 W ultrasound group, compared with the pure water group. The final moisture content also increased by 23.41 % in the 2.000 % NaHCO₃ group, without any significant change in the rehydration time. A Weibull model was better fitted for the TFSP rehydration in the control (R²≥0.993 3), ultrasound (R²≥0.990 5), and NaHCO₃ group (R²≥0.986 7). Both ultrasound and NaHCO₃ treatments slightly reduced the color of the re-hydrated TFSP, whereas, there was a great increase in the water holding capacity and immobilized water content. There was some variation in the hardness, chewiness, and degree of texturization of re-hydrated TFSP, without the outstanding difference in the springiness. The 400 W ultrasound group was the highest degree of texturization, 41.80 % higher than the control. Meanwhile, the 0.250 % NaHCO₃ group reached the smallest hardness, which was 54.17% smaller than the control. Scanning electron microscope (SEM) observation showed that the microstructure of rehydrated TFSP was changed by the ultrasound and NaHCO₃. Specifically, the pore size was enhanced to accelerate the water transport rate and the water holding capacity. Therefore, the ultrasound should be chosen to assist the TFSP rehydration, if the maximum degree of texturization was taken as the main evaluation index. By contrast, the NaHCO₃-assisted rehydration effect should be selected, if the minimum hardness was taken as the main evaluation index. This finding can provide a theoretical basis and reference to develop TFSP products with excellent qualities under different rehydration modes.