BIOCHEMICAL CHARACTERISTICS OF THE PROTEI N CONSTITUENTS OF CRAB ANALOGS PREPARED BY EXTRUSION-COOKING

This study concerns an experimental crab analog (0.63 w:w water, 0.23 w:w protein) and a commercial crab analog (0.82 w:w water, 0.14 w:w pr otein), both prepared by extrusion cooking of mixes containing Alaska pollack surimi and egg white powder. Protein solubility was studied at pH 8.0 and 10.6 in the presence of various dissociating agents. Solub le protein extracts were analyzed by SDS-PAG-Electrophoresis. Results were compared to those from an experimental heat-induced gel (kamaboko type), having the same composition as the experimental crab analog. T he heat-induced gel appears to be mainly stabilized by non-covalent in teractions (hydrophobic, hydrogen and electrostatic). Myosin heavy cha ins, which participate to the formation of soluble high molecular weig ht aggregates, may be directly involved in the gel network. The solubi lization of protein constituents from both extruded analogs requires s trong dissociating conditions. Electrophoregrams show extensive molecu lar rearrangements of both myofibrillar and egg white proteins. The in tensity of the extrusion process appears to be responsible for reactio ns such as hydrolysis and/or polymerization of polypeptide chains. Pro tein texturization by extrusion cooking probably involves the formatio n of numerous intermolecular covalent bonds (disulfide, probably isope ptide, but not lysinoalanine).