Abstract
The effects of different ultrasonic pretreatments (120-600 W, 20 min; 360 W, 10-30 min) on the gel properties of shrimp surimi were investigated. Gel properties and protein functional properties were analysed to clarify the mechanism of action of ultrasound. The gel strength, water holding capacity and surface hydrophobicity of shrimp surimi gel increased initially and then decreased with the increase in ultrasound power or time, but the change in total sulfhydryl content showed the opposite trend, which indicated that proper ultrasound pretreatment could improve the gel properties of shrimp surimi, expand the protein to a greater extent and expose more SH groups and hydrophobic groups. According to scanning electron microscopy observation, ultrasound made shrimp surimi gel form a denser gel network. Fourier transform infrared analysis indicated that the α-helix content in shrimp surimi gel decreased initially and then increased with the increase of in ultrasound power or time, whereas the change in β-sheet content showed the opposite trend. And the protein was the most stable in 360 W/20 min pretreatment. SDS-PAGE patterns showed that proper ultrasound inhibited the degradation of actin and troponin C. In addition, dynamic rheology illustrated that the G' values of the ultrasonic pretreatment group were higher than that of the control group, indicating that ultrasound could improve the elasticity and stability of shrimp surimi gel. The results suggested that the shrimp surimi gel pretreated by 360 W/20 min ultrasound showed the best gel properties. Furthermore, the correlation between the indexes affecting the properties of the gel was analyzed. This study provides a new technical means to improve the gel properties of shrimp surimi.