Texturization of Chum Salmon Muscle Harvested during Spawning Migration (Bunazake)

High Moisture Extrusion with Twin Screw Extruder Part III

Abstract

Chum salmon during spawning migration, called Bunazake in Japan, has not enough taste and protein suitable for conventional fish products and therefore, the new processing of Bunazake has been required to use them as one of possible food protein resources. Bunazake muscle was heated by boiling and removed its excess water with a single screw press to make Bunazake flake, and then examined its transformation to a texturized fish product with a twin-screw extruder. The extruder used in this study was a fully intermeshing co-rotating twin screw type equipped with a cooling die or a molding unit (Mitsubishi FT 60-N, screw diameter 60mm, L/D=20). There were some difficulties to texturize Bunazake flake to continuous fibrous products with the cooling die. However, 10% addition of wheat flour enabled the continuous extrusion cooking of Bunazake flake and enhanced the fibrous protein matrix formation in the extrudete, accompanying the reduction of extrusion pressure. The molding unit was found suitable to make large extruded meat lump regardless of the material composition. The microstructure and breaking strength of the extrudates revealed that the added wheat flour was distributed into the protein matrices to prevent them from fusion, and improve the alignment of fibrous fish protein matrix. These results suggest that the addition of other component such as wheat flour is one of possible means to control the formation of protein matrix and its alignment in the extrudate. SDS-PAGE showed that the addition of wheat flour enhanced the reduction of solubilty of Bunazake muscle protein. It is likely that wheat flour promotes the formation of cross-linking of proteins such as isopeptide bonding, a condensation reaction, by holding the water produced through the reaction.