Abstract: From the perspectives of protein structure and water distribution, the mechanism of the change in the water-holding capacity (WHC) of beef muscle during superchilled (-4 ℃), chilled (2 ℃) and frozen (-18 ℃) storage were investigated in this study. Superchilled samples exhibited significantly higher juice loss and cooking loss than chilled and frozen counterparts (P < 0.05), indicating the poorest WHC among all samples. During superchilled storage, the relaxation time of water was gradually prolonged; the content of bound water remained stable, the content of immobilized water decreased, and the percentage of free water increased (P < 0.05). As the storage time increased, total and free sulphydryl contents significantly decreased, and protein surface hydrophobicity significantly increase for all storage conditions (P < 0.05). At lower storage temperature, the rate of change was slower. Superchilled storage did not induce severe proteolysis of myofibrillar proteins. The denaturation degree of proteins in superchilled samples was higher at the late stage of storage, thereby improving the fluidity of immobilized water located in the myofibrillar protein network. Partial immobilized water was transformed into free water, thus leading to lower WHC of superchilled beef muscle.

Key words: beef muscle; superchilled storage; myofibrillar protein denaturation; moisture mobility