Effect of extrusion cooking on in vitro digestibility of low value aquatic protein

The waste scraps from the North Pacific squid processing were used as raw materials. Effect of extrusion process parameters on in vitro digestibility of extruded squid protein using a twin screw extruder was studied. A three-factor quadratic regression rotation combination design was adopted to analyze effects of feed moisture, barrel temperature, screw speed and their interactions on in vitro protein digestibility. Results showed that polynomial regression equations of process variables with in vitro protein digestibility were obtained with R²=0.896. Regression equations were highly credible. The optimal extrusion cooking conditions were obtained as follows: feed moisture 40%, barrel temperature 140°C and screw speed 25 Hz. Under these conditions, the in vitro protein digestibility could be up to 83.99%. Compared with normally processing methods, extrusion cooking showed the highest protein digestibility.