Ultrastructural and rheological changes during the gelation of giant squid (Dosidicus gigas) muscle

The giant squid or dosidicus (Dosidicus gigas) is normally shipped frozen from the coasts of America. During the period prior to freezing- when conditions are not always optimum - and during frozen storage, the functional capacity of the muscle proteins declines, rendering the material useless for certain processes such as conversion to gel. This paper examines the reasons for the lack of a good gel-forming capacity as measured both theologically (breaking force, breaking deformation and gel strength) and in terms of ultrastructure (scanning microscopy). The study was carried out at four different temperatures known to be critical for fish muscle protein gel formation, and at two salt concentrations. At 35 degrees C the structure was spongier in gels made with 1.5% NaCl, although a true gel was still not formed, as shown by rheological measurements. Above 30 degrees C, the ultrastructure became more cellular, particularly in samples made with 2.5% NaCl, at which concentration gel strength values were higher. However, at neither salt concentration nor at any of the experimental temperatures was the mesh as spongy as in other fish gels reported in the literature. The values of rheological analysis and folding test were correspondingly low.