Quality Change of Crayfish (Procambarus clarkii) Tail during Frying

Sensory evaluation, texture analyzer, low field-nuclear magnetic resonance (LF-NMR) and scanning electron microscope were used in this study for analyzing the changes of moisture, sensory quality, color, texture and microstructure of crayfish tail during frying, and the correlation between relaxation time and related indexes was analyzed. The results showed that: With the increasing of frying temperature and frying time, the moisture content decreased. LF-NMR imaging showed that the water was removed gradually from the outside to the inside. The peak area and relative proportion of relaxation time T₂₂ decreased, which showed that the immobilized water was removed mainly during frying. With the decrease of water content of fried crayfish tail, the brightness of color (L^* value) and the red value (a^* value) decreased, and yellow value (b^* value) rised, at the same time the hardness, elasticity and chewiness of crayfish meat increased gradually. Scanning electron microscope images showed that muscle fibers contracted and the gap became dense. The happiness and chewiness indexes of crayfish tail were best when the water content was 60.5%. At this point, the hardness was 24.55~25.64 N, the elasticity was 3.52~3.57 mm, the cohesion was 0.7 Ratio, and the chewiness was 54.6~56.5 mJ. Correlation analysis showed that, T₂₂ was negatively correlated with hardness, elasticity, cohesiveness and chewiness (P<0.05). The texture quality of the fried crayfish tail could be predicted by the LF-NMR imaging and the relaxation time T₂₂ peak area ratio. It would provide some theoretical guidance for the frying process of crayfish tail．