Abstract: In order to improve gel properties of porcine myofibrillar protein, we examined the effect of ultrasonic and/or transglutaminase (TG) treatment on gel strength, hardness, elasticity, water-holding capacity and chemical forces of heat-induced myofibrillar protein gels. We also investigated the effect on structural properties of?myofibrillar protein?by protein secondary structure analysis, differential scanning calorimetry and ultraviolet absorption spectroscopy. The results showed that the combined treatment could more significantly modify the properties of myofibrillar protein than either treatment alone. Compared with the control group, the content of sulfhydryl groups decreased, and water-holding capacity, whiteness value and hydrophobic interaction force increased; gel strength, hardness and elasticity values were enhanced by 3.57, 3.65 and 1.15 times in the combined treatment group, respectively. The results of structural analysis indicated that the combined treatment increased the thermal denaturation temperature of myofibrillar protein and resulted in a decrease in the relative content of alpha-helix with a simultaneous an increase in the relative contents of beta-sheet and beta-turn structure. In addition, this treatment increased the ultraviolet absorbance. The modified protein structure was conducive to improving the formation of myofibrillar protein gel. These results provide a theoretical basis for comprehensive utilization of myofibrillar protein.

Key words: myofibrillar protein, ultrasonic, transglutaminase, gel properties, protein structure