反复冷冻-解冻对猪肉品质特性和微观结构的影响

 【目的】反复冷冻-解冻对猪肉品质特性和微观结构的影响，为肉类保鲜提供科学依据。【方法】猪肉背最长肌经过反复冻结（-26℃，7 d）、解冻（18℃室温流水解冻）后，测定肌肉解冻损失(thawing loss, TL)、煮制损失（cooking loss，CL）、剪切力（cutting force，CF）、微观结构、肉的颜色（(L*，a*和b*值)）、硫代巴比妥酸值（thiobarbituric acid reactive substances，TBARS）等指标。【结果】随着冷冻-解冻次数的增加，猪肉的TL、CL、TBARS、L*和b*值明显增大(P＜0.05)，肌纤维排列混乱断裂、肌纤维间隙增大、结构疏松、肌内膜破裂，a*值逐渐变小;冷冻-解冻1次后猪肉CF明显高于新鲜猪肉，超过3次后，CF逐渐变小。【结论】反复冷冻-解冻过程严重破坏了肌肉微观结构、降低了猪肉品质。

Effect of Freeze-Thawing Cycles on the Quality Properties and Microstructure of Pork Muscle

【Objective】 The effects of freeze-thawing cycles on pork quality properties and microstructure were investigated. The purpose of this study was to provide a scientific basis for meat preservation. 【Method】 The porcine longissimus dorsi (LD) were frozen for 7 d under -26℃, then thaw by lotic water (room temperature, 18℃). The effects of freeze-thawing cycles on thawing loss (TL), cooling loss (CL), cutting force (CF), microstructure, color (L*, a*, and b*-values), TBARS (thiobarbituric acid-reactive substances) of pork were studied. 【Result】 The results showed that freeze-thawing cycles significantly increased the TL, CL, TBARS, L*-values and b*-values, and decreased a*-values (P＜0.05). The scanning electron micrograph of pork muscle showed that freeze–thawing cycles increased the space between fiber, torn and confused muscle fiber bundles, and breakdown muscle endometrial. The pork CF subjected one freeze-thawing cycle was significantly higher than that of fresh pork, and was gradually lower after multiple freeze-thawing cycles. 【Conclusion】 The results demonstrated that freeze-thawing cycles seriously damaged microstructure of muscle and declined the quality properties of pork.