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Two protein concentrates from jumbo squid fins (Dosidicus gigas) were elaborated. One of them was obtained via alkaline dissolution and subsequent isoelectric precipitation (alkaline protein concentrate [APC]) and the other was obtained via the traditional method (neutral protein concentrate [NCP]). The electrophoretic profile of the APC showed that the myosin heavy chain band disappeared, mainly due to the denaturation induced by alkaline solubilization or activation of alkaline protease. Concerning the quality of the gels, the folding test showed that gels obtained using APC were better than those obtained using NPC, but a texture profile analysis detected fracture in the APC gels. Regarding the interfacial properties, low emulsifying capacity was observed for both protein concentrates, and the APC was better than the NPC. Additionally, the foaming properties were excellent for both concentrates and were significantly better for APC. Therefore, the alkaline solubilization process for fin squid was suitable for the production of functional protein concentrates. Practical Applications One of the challenges of the fishing industry is to achieve an integral use of fishing resources. Jumbo squid is an abundant resource in Northwest Mexico and its by-products generate a great of waste, which are an environmental problem. Viscera, heads and fins are the main waste of jumbo squid. Fins are about 10% of the total animal; therefore, their exploitation is a good option for this industry. Hence, this study compares and evaluates the functional properties of the protein concentrates obtained from squid fins via alkaline dissolution and subsequent isoelectric precipitation and the conventional methodology (water washing muscle) to determine the most feasible method of obtaining protein concentrates from squid fins.

Jumbo squid (Dosidicus gigas) is an important commercialized fishery in Mexico; however, during its post-catch processing, several physicochemical changes occur in flesh, which could result in texture modifications. In this research, changes in water-holding capacity, protein solubility (PS), firmness, fibrils microstructure, and color of squid muscle (mantle, fins, and arms) during cooking (30 min at 100 °C) were evaluated. Throughout cooking were exhibited different shrinkage and weight loss behavior among three anatomical regions (p arms > mantle, whereas at ending cooking, mantle muscle required the lowest SF. Microscopic analysis revealed a major quantity of collagen fibers in fins and arm muscle suggesting its possible relation to their hardness, in both fresh and cooked state. Practical applications Jumbo squid (Dosidicus gigas) is an important marine resource in Mexico and many Asiatic and European countries. Its muscle (fins, arms, and mantle) edible items are commercialized and consumed in fresh, brined, and cooked presentations. Squid muscle protein structures (fibril and stromal) are organized different than fish as well as beef, pork and poultry; therefore its textural, physicochemical and sensorial (quality parameters) changes induced by cooking are distinctive. Squid meat acceptance by consumers is related mainly by texture than the taste or color attributes. Therefore, from economic point of view of domestic and large-scale markets, the establishment of best cooking conditions of squid became essential.

Connective tissue (CT) proteins in jumbo squid (Dosidicus gigas) play an important role because they are the responsible for the union between various cells; hence, there is a close relationship between their functions and muscle firmness during ice storage. In this study, the thermal resistance and solubility of the CT extracted from the fins, mantle and arms of jumbo squid during ice storage (20 days) was evaluated. The CT was fractionated based on solubility [NaCl-soluble (SSCT) and insoluble (ICT)]. The solubility of the CT was affected during ice storage. An increase in the thermal resistance of the SSCT after 10 days with a subsequent decrease was found in the mantle. Furthermore, the ICT was thermally more resistant than the SSCT in all the anatomical regions. Finally, the electrophoretic profile revealed that structural changes occurred, causing changes in its solubility, due to an increase in the thermal resistance. Practical Applications Jumbo squid (Dosidicus gigas) is an important seafood resource in Mexico, which is commercialized primarily iced and fresh-frozen. Its muscle connective tissue (CT) has different physicochemical characteristics that differ from other seafood products; it is thermally more resistant and might be responsible for the textural changes during ice storage. Moreover, specific studies about the behavior of CT proteins in such organism may result in improved post-catch management of jumbo squid muscle, focused on the processing of the species in the food industry or anywhere that CT proteins are used as raw material. The main objective of this research is to investigate solubility changes and thermal resistance of CT proteins of iced jumbo squid mantle.