Abstract: The effects of a combination of trehalose and mannitol (both 4 g/100 mL) on freeze-thaw-induced structural and functional changes of myofibrillar proteins from Oratosquilla oratoria were studied, aiming to provide a theoretical basis for the preservation of seafood products. In this study, 0, 1, 3 and 5 freeze-thaw cycles were performed on the experimental group with cryoprotectants and the control group without cryoprotectants. Protein carbonyl content, total sulfhydryl content, surface hydrophobicity, tryptophan fluorescence, storage modulus (G’), gel strength and water-holding property, gel microstructure, and emulsifying properties were determined to explore the cryoprotective effects of trehalose and mannitol. As the number of freeze-thaw cycles increased, protein carbonyl content and surface hydrophobicity increased significantly (P < 0.05), while total sulfhydryl content and tryptophan fluorescence intensity decreased significantly (P < 0.05). Protein aggregation was found to different extents and the gelation and emulsifying properties were reduced markedly. The addition of trehalose and mannitol effectively inhibited protein denaturation, reduced the changes in protein structure, increased the storage modulus (G’) of myofibrillar protein during thermal gelation, and improved the gel properties (gel strength and water-holding capacity and three-dimensional network structure), emulsifying activity and emulsion stability. Trehalose and mannitol could combine with functional groups of myofibrillar protein, thereby avoiding protein aggregation. In addition, by binding with water molecules, trehalose and mannitol could reduce the eutectic temperature, decrease the formation of ice crystals, retard protein aggregation, and prevent protein condensation and denaturation, thus improving the quality of mantis shrimp meat during freezing storage.

Key words: freeze-thaw cycles, Oratosquilla oratoria, trehalose, mannitol, protein oxidation, functional properties