Effect of Ultrasonic Pretreatment on the Textural Properties and Structure of Flaxseed Gum-Soybean Protein Isolate Composite Gels

Objective: This study aimed to investigate the impact of different ultrasonic power and time pretreatments on the structures and gel properties of the flaxseed gum and soybean protein isolate composite gel induced by TG enzyme. Methods: The structural characteristics, molecular conformation, and micro-network structures of the composite gel under varying ultrasonic conditions were analyzed using a texture analyzer, laser particle size meter, circular dichroism (CD), fluorescence spectrum, and scanning electron microscope (SEM). Results: The 50% power ultrasound pretreatment for 10 min could significantly improve the hardness, adhesiveness, chewiness, cohesiveness and water-holding property of the composite gel, and reduce its adhesiveness; after 50% power ultrasound pretreatment for 10 min, the α-helix and β-turn content of composite gel proteins decreased, and the content of β-folding and irregular curls increased, and the fluorescence intensity increased, which was conducive to the improvement of the functional properties of the gel. The microstructure of the composite gel became ordered from disorder, the network density increased, the pore diameter became smaller, and the pore wall was thickened; while after increasing the ultrasound power to 80%, the gel properties fluctuated only slightly and the microstructure was destroyed. Conclusion: 50% power ultrasound pretreatment for 10 min can significantly improve the gel properties and network structure of TG enzyme cross-linked flaxseed gum-soybean protein isolate composite.