Abstract: The aim of the present study was to establish the optimum onboard cooking process for jumbo squid (Dosidicus gigas) by using an independently designed onboard cooking device. The thermal denaturation temperature for squid protein was determined by using a differential scanning calorimeter (DSC). Box-Behnken design coupled with response surface methodology (RSM) was used to optimize the cooking parameters employing cooking loss and soluble protein content as response values. The longitudinal and transverse cross-sectional microstructure of cooked and raw squid muscle tissue was analyzed by scanning electron microscopy (SEM) and texture properties were measured. The changes in squid protein composition were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In addition, the total volatile basic nitrogen (TVB-N) content was determined to analyze the freshness of squid. The results showed that the fitting degrees of the two regression models developed were excellent and there was a good agreement between the actual experimental and the model-predicted values with small relative errors. The optimum cooking temperature, cooking time, and material-to-water ratio were determined to be 85 ℃, 11 min, and 1:2 (kg/L), respectively. The cooking loss was (25.53 ± 0.25)% and soluble protein content was (15.38 ± 0.16) mg/g under these optimized conditions. The transverse cross-sectional microstructure of squid muscle was less damaged by the cooking process, while the space among muscle bundles in the longitudinal cross-section was increased. SDS-PAGE showed that the small protein bands of cooked squid, such as squid tropomyosin, were diminished and even disappeared whereas the other ones were not changed significantly. The texture characteristics of squid were not significantly affected by cooking and the TVB-N value of onboard processed squid was (28.12 ± 0.34) mg/100 g.

Key words: Dosidicus gigas, onboard cooking, quality characteristics, freshness index