Effect of oxidation on the microbial transglutaminase-mediated cross-linking and gelation of myofibrillar proteins

The effect of protein oxidation in different salt concentrations on subsequent microbial transglutaminase (MTG) -catalyzed cross-linking reaction and gelation was studied. Myofibrillar proteins dispersed in three salt concentrations (0.15, 0.45 and 0.6mol/L NaCl) were oxidized at 4℃ for 2h and 24h, respectively, then treated with MTG in 0.6mol/L NaCl at 30℃ for 2h. Electrophoresis and solubility were used to study the effect of protein oxidation on MTG cross-linking reaction, and gel strength was used to study the effect of protein oxidation on gel properties when treated with MTG. The results showed that oxidation of myofibrillar proteins at three salt concentrations all promoted MTG-mediated cross-linking reaction , especially in high salt concentrations (relative increase induced by MTG was up to 47.8% ) . The gel strength of all samples significantly increased after MTG treatment (p<0.05) . Compared with myofibrilar protein oxidized in low salt concentration, the protein oxidized in high salt concentration formed much stronger gels. Moreover, the relative increase of gel strength for oxidized protein induced by MTG in all salt concentrations was higher than that of the nonoxidized. As a conclusion, excessive cross-linking was found undesirable for protein gelation.