Influences of multiple freeze-thaw (F-T) cycles on water status and distribution, microstructure and physicochemical properties of beef were investigated. Low-field nuclear magnetic resonance (LF-NMR) relaxation showed three water components were assigned to bound, immobilized and free water in beef matrix. With the increase of F-T cycles, the relaxation time and peak area of immobilized water decreased significantly (P < 0.05), which suggested the freedom and population of immobilized water decreased. T₁ and T₂ magnetic resonance images displayed a continuous decrease of water intensity in beef during multiple F-T cycles. The cryo-scanning electron microscopy results revealed repeated F-T cycles resulted in more and more large holes in the beef muscle fiber. The repeated F-T cycles also led to decrease of pH value, WHC, L* and a* values, hardness, springiness, cohesiveness and resilience, and the increase of thawing loss, cooking loss, b* and TBARS value. Partial least-squares regression models stated the potential of LF-NMR to predict the quality of beef as a non-destructive method.

研究了多次冻融循环对牛肉水分状况，分布，微观结构和理化特性的影响。低场核磁共振（LF-NMR）弛豫表明，将三种水成分分配给牛肉基质中的结合水，固定化水和游离水。随着FT循环次数的增加，固定化水的弛豫时间和峰面积显着减少（P  <0.05），这表明固定化水的自由度和种群减少。T ₁和T ₂磁共振图像显示，在多个FT循环中，牛肉中的水分强度持续降低。低温扫描电子显微镜结果表明，重复的FT循环导致牛肉肌肉纤维中的孔洞越来越大。重复的FT循环还导致pH值，WHC，L *和a *值，硬度，弹性，内聚力和回弹力降低，并且解冻损耗，蒸煮损耗，b *和TBARS值增加。偏最小二乘回归模型表明，LF-NMR可以预测牛肉作为非破坏性方法的质量。