Effects of ultrasonic treatment on the structure and rehydration peculiarity of freeze-dried soy protein isolate gel

Abstract

• The structure of freeze-dried SPI gel was affected by ultrasonic treatment. • The storage modulus of freeze-dried SPI gel was affected by ultrasonic treatment. • Ultrasonic treatment affects network structures of freeze-dried SPI gel. • Ultrasonic treatment affects the rehydration peculiarity of freeze-dried SPI gel. Different levels of ultrasonic power (0, 100, 200, 300, 400, and 500 W) were applied to soybean protein isolate [SPI] solution to evaluate the effects of ultrasonic treatment (4°C) on the microstructure and rehydration peculiarity (rehydration kinetics, texture profile analysis [TPA], water-holding capacity, and water distribution) of freeze-dried SPI gel. Suitable ultrasonic treatment (4°C) reduced the average size and increased the energy storage modulus of SPI solution relative to those of untreated SPI solution. The formed gel has a uniform and dense network structure. The improved the water-holding capacity and texture, and enhanced the capillary percolation of freeze-dried SPI gel during rehydration. And enlarged the size of holes in rehydrated SPI gel and made the water release rate, relaxation time T 22 , M 22 , gel hardness of rehydrated SPI gel were significantly higher than that of fresh SPI gel ( P < 0.05). Therefore, freeze-dried SPI gel with a fine texture and high rehydration rate can be prepared when ultrasonic power of 300 W.