Abstract: In this study, soy protein isolate (SPI) was treated with hydrodynamic cavitation (HC) based on swirling. The texture properties, water-holding capacity, rheological properties, intermolecular force, microstructure, and secondary structure of transglutaminase-catalyzed SPI gel were determined to evaluate the effect of HC on the transglutaminase-catalyzed gelation behavior of SPI. The results showed that the gel strength (P < 0.05), water-holding capacity (P < 0.05), and storage modulus of the transglutaminase-catalyzed gel formed from SPI treated with HC for 30 minutes were increased significantly compared with the gel formed from untreated SPI. The intermolecular force for gel formation was changed. The contents of ionic bonds, hydrogen bonds and hydrophobic interactions were significantly decreased (P < 0.05), while the contents of disulfide bonds and non-disulfide covalent bonds were significantly increased (P < 0.05). Scanning electron microscopy showed that the transglutaminase-catalyzed gel formed from SPI treated by HC had smaller pores and more compact and uniform microstructure. The results of infrared spectroscopic analysis showed that the secondary structure of the gel was also changed by HC treatment. The contents of β-sheet and β-turn were increased significantly (P < 0.05), while the contents of α-helix and random coil were decreased significantly (P < 0.05). Therefore, HC treatment can improve the performance of transglutaminase-catalyzed SPI gel under certain conditions, and it may be used as an effective method in the food industry.

Key words: hydrodynamic cavitation; soy protein isolate; transglutaminase; gel