Abstract: This study investigated the effect of different cooking conditions (citric acid concentration and cooking time) on the quality of Fenneropenaeus chinensis as evaluated in term of relative activity of polyphenol oxidase, moisture, water-holding capacity, astaxanthin content, protein content and extraction yield, color, texture, sensory evaluation, and scanning electron micrograph. The results showed that the complete inactivation time of polyphenol oxidase in shrimp head was gradually shortened with the increase of citric acid concentration. However, too high citric acid concentration was not conducive to the taste of shrimp, and therefore the optimal concentration was determined to be 4 g/L. With prolonging cooking time, the moisture and water-holding capacity of shrimp muscle decreased gradually, the astaxanthin content increased first and then decreased, and the total protein content declined continuously. Myofibrillar and sarcoplasmic proteins were mostly denatured after 2 min of cooking. During the cooking process, L* and a* values increased first and then decreased, while b* values increased continuously. Hardness, cohesiveness and chewiness increased continuously, while the opposite trend was observed for elasticity. Sensory evaluation results showed that shrimps cooked for 4 min scored highest in sensory scores for each quality attribute and in overall sensory scores. Scanning electron microscopy (SEM) results showed that shrimp muscle fibers were gradually denatured by heating, resulting in a decrease in regularity, an increase in the gap between muscle fibers and aggravation of dimensional breakage. Taken together, the optimum cooking time was determined to be 4 min. The results of this study can provide a theoretical basis for shrimp product enterprises to optimize the production process and to improve product quality in the future.

Key words: Fenneropenaeus chinensis, cooking in boiling water, citric acid, polyphenol oxidase, astaxanthin, quality