Changes in tissue structure and rheological properties of squid were studied as related to cooking time using the mantle of squid just after instant killing. Collagen fibers of integument were tautly shrunk and voids were formed among the fibers by cooking. Muscle fibrils were considerably dehydrated and disconnected. Rupture energy (RE) for breaking raw squid parallel to the circular musculature was greater than that for breaking across the circular musculature. Cooking softened squid flesh and reduced RE both in parallel and transverse breaking of circular musculature. Reduction in RE was considerable in parallel breaking but not notable in transverse breaking.

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Histological and physicochemical changes in the mantle muscle tissue of squid (Sepioteuthis lessoniana) during storage were studied. When raw squid mantles were broken parallel to the circular musculature, the rupture energy (RE) was significantly lowered along with the storage. In the case of breaking across the circular musculature, the RE was slightly lowered but the yield point (YP) in the stress-strain curve shifted to a larger strain during storage. In the case of heated squid meat, the YP shifted to a lower strain during storage. The electron microscopic observation of the muscle tissue of raw squid indicated that a number of voids appeared between the muscle bundles and the muscle fibers during storage, and after cooking, obvious detachment was observed between the muscle fibers and muscle bundles. No significant changes in the molecular sizes of major protein components (muscle fibril proteins) were observed, indicating that the muscle fibril proteins were not degraded.

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TO CLARIFY differences between raw squid and softened dried squid, dried squid mantle was softened under various conditions, degree of swelling and certain properties were measured, and the musculature was examined by electron microscopy. Swelling the dried squid to the original level of raw squid required softening in three steps: presoaking, alkali-soaking, and post-soaking. The alkali-soaking was mainly responsible for the swelling effect. Resulting properties were largely changed from those of raw squid. Electron microscopy showed much water permeation throughout the muscle fibrils and fibers, while there was almost no permeation of water inside the individual fibrils.