Abstract: Endogenous transglutaminase (TGase) is closely related to the properties of surimi gel, and irradiation may cause changes in the structure and activity of TGase. In order to investigate the effect of electron beam (EB) irradiation at different doses on its quality, TGase activity of hairtail (Trichiurus haumela) surimi was determined as well as its optimum temperature and pH, and the conformation of TGase was analyzed by Fourier transform infrared and circular dichroism spectroscopy. Moreover, changes in the gel strength and water-holding capacity of surimi gel were examined to investigate the mechanism underlying the effect of EB irradiation on the endogenous TGase and gel properties of surimi. Results showed that the activity of TGase increased first and then decreased with the increase in EB irradiation dose. Irradiation at a dose of 5 kGy significantly increased the activity of TGase, and gave the highest gel strength and water-holding capacity. The optimum pH of TGase was 8.0 for each dose group, and the optimum temperature was 40 ℃ for all dose groups except 9 kGy and control group. Furthermore, EB irradiation could transform the secondary structure of TGase, leading to the lowest contents of α-helix and β-turn, and the highest contents of β-sheet and random coil at a dose of 5 kGy. Therefore, EB irradiation can affect the secondary structure and activity of TGase in hairtail surimi, at an appropriate dose promote the transformation of α-helix and β-turn into β-sheet and random coil. In addition, it can improve the activity of TGase and consequently promote the gelation of hairtail surimi.

Key words: electron beam irradiation, endogenous transglutaminase, secondary structure, hairtail surimi, gel strength