微冻贮藏对牛肉保水性的影响

本实验以冷藏（2 ℃）和冷冻（－18 ℃）作为对照组，从肌原纤维蛋白结构和水分迁移等方面分析了微冻（－4 ℃）贮藏条件下牛肉保水性变化的机制。结果表明：微冻贮藏牛肉的汁液损失率和蒸煮损失率显著高于冷藏和冷冻处理组（P＜0.05），保水性最差。微冻贮藏过程中，牛肉中的水分弛豫时间逐渐变长，结合水相对含量无明显变化，不易流动水相对含量显著下降，自由水相对含量显著上升（P＜0.05）。随着贮藏时间的延长，3 种贮藏方式下牛肉的总巯基含量和活性巯基含量均显著下降，蛋白质表面疏水性显著上升（P＜0.05），且贮藏温度越低，变化速率越慢。微冻贮藏过程中，牛肉肌原纤维蛋白降解程度较低，贮藏后期蛋白质变性程度较高，提升了肌原纤维蛋白网络中不易流动水的自由度，使得部分不易流动水转化为自由水，导致了微冻牛肉较差的保水性。

Effect of Superchilled Storage on Water-holding Capacity of Beef Muscle

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.