Abstract: This study aimed to develop a process for producing high-quality prepared grass carp products. The effects of glutamine transaminase (TG), soy protein isolate (SPI) and NaCl concentration, blending time, and fish meat to surimi ratio on the gel strength, water-holding capacity, whiteness and sensory score of grass carp surimi were investigated using one-factor-at-a-time method, and further all these parameters except fish meat to surimi ratio were optimized using response surface methodology based on gel strength. Furthermore, we evaluated the efficacy of the ethanolic extract of Euryale ferox salisb seed shells in inhibiting the quality deterioration of the prepared fish product during refrigerated storage. The results showed that TG, SPI and NaCl concentration and blending time had significant effects on the gel strength of grass carp surimi (P < 0.05). There was a significant interaction among NaCl and TG concentration, and blending time (P < 0.05). The error between the experimental and the model-predicted values was within 5%, and the optimized process parameters were as follows: SPI 3.20%, TG 3.83%, NaCl 3.62%, blending time 27 min, and ratio of surimi to fish 4:1. The extract of Euryale ferox salisb seed shell when used at a concentration of 5 mg/mL could inhibit the quality deterioration of the prepared fish product during cold storage and prolonged the shelf-life. The prepared fish product in this study had good texture and gel strength and long shelf life under refrigerated conditions. This study provides theoretical support for the development of prepared grass carp products.

Key words: grass carp; prepared fish products; gel strength; Euryale ferox salisb seed shell extract; quality