Abstract:

To study the effect of ultrasonic treatment on structure and gel properties induced by transglutaminase (TG)
of soybean protein isolate (SPI), the change in particle size, solubility, surface hydrophobicity, secondary structure,
microstructure and gel properties of ultrasonicated SPI was measured in comparison to the untreated one. Results indicated
that ultrasonic pretreatment could reduce particle size and increase solubility and surface hydrophobicity as well as random
coil content of SPI. Ultrasonic pretreatment could decrease α-helix content without causing any significant changes in the
contents of β-sheet and β-turn. SPI gels induced by TG could be promoted by ultrasonic treatment, and the gel had denser
and more uniform microstructure when compared with the untreated gel. When treated for 60 min, the gel strength and waterholding
capacity were 146.57 g and 94.27%, respectively, showing an increase by 62.12% and 3.66%, respectively. Correlation analysis
showed that the particle size of SPI dispersion was negatively correlated with solubility, gel strength and WHC.

Key words: ultrasonic, soybean protein isolate (SPI), structure, transglutaminase (TG), gel property