Comparative studies on the yield and characteristics of myofibrillar proteins from catfish heads and frames extracted by two methods for making surimi-like protein gel products

Fish protein isolates (FPI) were recovered from catfish heads and frames by alkaline extraction (AE) and salt extraction (SE) and made into surimi-like gels. Protein patterns and content, moisture, color, and texture of cooked protein gels were compared with commercial products. Sodium-dodecyl-sulfate poly acrylamide gel electrophoreses (SDS-PAGE) indicated that the integrity of major myofibrillar proteins was maintained during the extraction process, and the protein patterns were almost the same with that of the commercial surimi products. The yields of AE-FPI (heads: 36%; frames: 55%) were much higher (p < 0.05) than that of SE-FPI (heads: 9%; frames: 16%). Firmness of cooked protein gels made from heads was similar with that made from frames. Firmness of cooked protein gels made from FPI extracted by the SE method (heads: 0.45 kg/cm2; frames: 0.43 kg/cm2) was significantly lower (p < 0.05) than that made from FPI extracted by the AE method (heads: 1.96 kg/cm2; frames: 1.85 kg/cm2).