Effect of microbial transglutaminase and setting condition on gel properties of blend fish protein isolate recovered by alkaline solubilisation/isoelectric precipitation

The effect of microbial transglutaminase (M-TGase) (0-0.6 units g(-1) sample) and setting condition (25 degrees C/180 min, 30 degrees C/120 min, 35 degrees C/60 min and 40 degrees C/30 min) on gel properties of blend protein isolate of gutted kilka and silver carp was studied. The protein isolate provided a good substrate for M-TGase activity so that a low amount of M-TGase (0.2 unit g(-1) sample) substantially improved textural properties and water holding capacity (WHC) of the gels. Breaking force of the gels was positively affected by M-TGase up to 0.6 unit g(-1) sample, but it negatively affected their WHC. Prior setting at 25-35 degrees C increased the breaking force of proteins compared to directly heated gel, resulting in maximum breaking force at 35 degrees C/60 min. However, the setting at 40 degrees C/30 min caused proteolysis, which was reflected in higher amounts of TCA-soluble peptides and gel weakening. Denser microstructure and higher myosin heavy chain polymerisation observed in the gels which experienced the setting was well correlated with improvement in textural properties.