Effect of endogenous transglutaminase on setting of surimi from freshwater fishes

The setting properties at 25 ℃ and 40 ℃of freshwater fish surimi from three species,i.e.tilapia,bighead carp and dace were studied.SDS-polyacrylamide gel electropHoresis(SDS-PAGE),the test of the activity of endogenous transglutaminase(TGase)and the effect of TGase activator(calcium chloride)and inhibitors(EDTA,ammonium chloride)on the setting properties of the surimi were carried out to investigate the function of TGase during setting.The results showed the gel strength of the surimi gels from three species made by setting at 25 ℃ or 40 ℃could be increased markedly.SDS-PAGE declared the intensity of the myosin heavy chain(MHC)of the setting gels all decreased suggesting the cross-linking of MHC catalyzed by endogenous TGaseduring setting.The optimal setting temperature of tilapia and bighead carp surimi was found to be 40 ℃,whilethat of dace surimi was 25 ℃,which was coincided with the activity of endogenous TGase.The gel strength ofthe surimi gels from three species was considerably elevated with the addition of calcium chloride,which wascoincided with the decrease of the intensity of their MHCs.On the other hand,the gel strength was decreasedmarkedly with the addition of EDTA and ammonium chloride,which was in agreement with the increase of theintensity of their MHCs.The above results confirmed that endogenous TGase played an important role duringthe setting of the freshwater fish surimi.