丙二醛对牛肉线粒体高铁肌红蛋白还原能力的影响

研究了体外孵化条件下脂质氧化产物丙二醛对牛肉线粒体膜通透性、微观结构及其电子传递链调控的高铁肌红蛋白还原能力和NADH依赖型高铁肌红蛋白还原酶活力的影响。结果表明:在p H值5.6(模拟贮藏条件)和p H值7.4(模拟生理条件)条件下,线粒体与丙二醛孵化后膜通透性、孵化液体荧光强度均比对照组显著增大(P0.05),线粒体微观结构出现肿胀变形、嵴消失、空泡状等现象。当p H值为7.4时,膜通透性、荧光强度显著高于前者(P0.05),说明在生理p H值条件下丙二醛更易与线粒体膜作用进而对其结构造成破坏。琥珀酸盐能够促进牛肉线粒体电子传递链调控的高铁肌红蛋白还原过程,在p H值5.6和p H值7.4条件下添加琥珀酸盐孵化9 h后,高铁肌红蛋白相对含量分别减少了21.70%和12.87%(P0.05)。但是在反应体系中加入丙二醛孵化9 h后,高铁肌红蛋白的还原量分别比未添加时降低了15.68%和3.83%(P0.05)。丙二醛同样能够抑制牛肉线粒体NADH依赖型高铁肌红蛋白还原酶的活力,其活力在上述p H值条件下分别降低了48.97%和47.80%(P0.05)。综上可知,丙二醛能破坏牛肉线粒体结构,抑制线粒体还原高铁肌红蛋白的能力,对新鲜牛肉保持其色泽稳定性是不利的。因此,降低牛肉贮藏过程中脂质氧化程度、维持线粒体正常的呼吸作用,对于保护牛肉色泽稳定性具有重要意义。

Effects of Malondialdehyde on Metmyoglobin Reduction Ability of Bovine Muscle Mitochondria

The effects of malondialdehyde on bovine mitochondrial microstructure and metmyoglobin reduction ability were evaluated by measuring membrane permeability, malondialdehyde binding capacity, microstructure, electron transport chain-mediated metmyoglobin reduction and NADH-dependent metmyoglobin reductase activity. Compared with control groups, mitochondria incubated with malondialdehyde were increased significantly ( P <0.05) from membrane permeability and fluorescence intensity. As a result, mitochondria were swollen, mitochondrial cristae were partially disappeared and some of which were slightly vacuolated. Mitochondria incubated with malondialdehyde at pH value of 7.4 (storage condition) had a greater membrane permeability and higher fluorescence intensity ( P <0.05) than those of at pH value of 5.6 (physiological condition), which indicated that malondialdehyde reacted with mitochondrial membrane more easily under physiological condition, resulting in more serious injury to membrane. Succinate promoted the electron transport chain-mediated metmyoglobin reduction, the relative metmyoglobin contents were decreased by 21.70% and 12.87% ( P <0.05) at pH values of 5.6 and 7.4 compared with control groups (without succinate), respectively. Nevertheless, mitochondrial electron transport chain-mediated metmyoglobin reduction was inhibited when incubated with malondialdehyde, the reduction amounts of metmyoglobin were decreased by 15.68% and 3.83% ( P <0.05) at pH values of 5.6 and 7.4 compared with control groups (without malondialdehyde), respectively. In addition, NADH-dependent metmyoglobin reductase activity was also inhibited by malondialdehyde, which was decreased by 48.97% and 47.80% ( P <0.05) respectively when incubated with malondialdehyde at pH values of 5.6 and 7.4. In conclusion, malondialdehyde could injure the microstructure of mitochondria and inhibit the mitochondria mediated metmyoglobin reduction, which was disadvantageous to color stability of fresh beef. Therefore, it is meaningful to reduce lipid oxidation and maintain mitochondrial respiratory function for protecting color stability during storage.