Hydrolyzed Fish Muscle as a Modifier of Rice Flour Extrudate Characteristics

The effects of fish protein hydrolysis time and fish solids level on macroscopic properties of extrudates were investigated. Arrowtooth flounder muscle was autolyzed for varying times; hydrolyzed muscle was recovered, dried, blended with rice flour at varying levels, and extruded using a twin‐screw extruder. Hydrolysis beyond 5 min had little effect on extrudate properties. Addition of hydrolyzed fish solids strikingly decreased the apparent density and breaking strength but increased extrudate porosity and expansion ratios. In general, the effect was greater when the level of fish solids was higher. Opposite and expected trends were observed for blends with unhydrolyzed fish solids. Fish solids level played a dominant role in increasing true density.