| Summary: | Hoki (Macruronus novaezelandiae) is an important commercial fish in the New Zealand Exclusive Economic Zone. The resource remains underutilized with only a small proportion of the 250,000 tonnes Total Allowable Catch presently being made into added value products. There is interest in producing surimi, a refined, stabilized form of fish mince, from hoki. Surimi is an intermediate raw material used for the production of a range of fabricated foods. The rheological properties of these gel-based foods are of key importance for their consumer acceptability. The quality of surimi is determined predominantly by the gel-forming ability of the myofibrillar protein of the raw material fish used in the process. These properties change with chilled and frozen storage of the fish. The objectives of this study are to develop methodology to test the gel-forming ability of surimi; to investigate the changes in gel-forming ability of hoki with chilled and frozen storage, and to evaluate the rheological methods used in these studies. The implications with respect to a domestic surimi industry are discussed. The rheological properties of gels made from hoki stored for various times, chilled or frozen, were determined using two failure tests, namely the puncture test and the torsion test. The puncture test is an empirical method commonly used in the surimi industry, where a 5 mm diameter spherical probe is driven into the gel at constant plunger speed. The force and deformation at failure are used to describe the mechanical properties of the gels. The torsion test is a fundamental method whereby a pure shear state is obtained by applying a twisting moment about a central axis. The shear stress and true strain at failure are calculated and used to follow the changes in gel properties with time. The strength of gels decreased as the fish spoiled on chilled storage. The decline appears to be slower than that reported for other fish such as Alaska pollock. Even after 10 days storage the gel strength was such that hoki would still have ...
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