Abstract:To investigate the effects of the number of freeze-thaw cycles on the physicochemical properties of myofibrillar proteins of bay scallops and the gel properties of scallop surimi.The changes in physicochemical and structural properties of adductor muscle and myofibrillar protein of bay scallops after one，two，and four freezethaw cycles were investigated.The results indicated that as the number of freeze-thaw cycles increased，the content of the myofibrillar protein，total sulfhydryl，and active sulfhydryl in the adductor muscle of bay scallops decreased.The content of myofibrillar protein decreased by 54.1% at the fourth freeze-thaw cycle，and the total sulfhydryl and the active sulfhydryl decreased by 62.7% and 58.3%，respectively.The surface hydrophobicity increased significantly（P<0.05）；the protein α-helical structure was gradually unwound and partially transformed into β-sheet and random coil structure.The endogenous tryptophan fluorescence intensity also decreased.The gel results showed that the water-holding capacity，hardness，and elasticity of the shellfish gel decreased significantly（P<0.05）.After the fourth freeze-thaw cycle，the water-holding capacity of the shellfish gel decreased by 6.1%，and the hardness decreased by 41%.The scanning electron microscopy results showed that the three-dimensional network structure of the gel changed from dense to loose and porous.