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This study investigated the effect of lysosomal iron involvement in the mechanism of mitochondrial apoptosis on bovine muscle protein degradation during postmortem aging. Six crossbred cattle were studied to evaluate intracellular reactive oxygen species (ROS), antioxidant enzyme activity, lysosomal membrane stability, mitochondrial dysfunction-induced apoptosis, desmin and troponin-T degradation in both control and iron chelator desferrioxamine (DFO) groups. Results showed that lysosomal iron induced ROS accumulation and lysosomal membrane destabilization by decreasing the antioxidant enzyme activity (P 0.05). Subsequently, lysosomal dysfunction mediated by iron increased mitochondrial membrane permeability and decreased mitochondrial membrane potential, thereby enhancing Bid and cytochrome c release and caspase-9/-3 activation (P 0.05). Ultimately, lysosomal iron mediated lysosomal-mitochondrial apoptosis increased the postmortem bovine muscle desmin and troponin-T degradation (P 0.05). The results indicated that lysosomal iron contributes to postmortem meat tenderization through the lysosomal-mitochondrial dysfunction-induced apoptosis pathway.

This study investigated the effects of ultrasonic on the quality of puffed cowhide and of ultrasonic treatment on various parameters, such as color, expansion rate, microstructure, texture, and sensory score. Under all experimental conditions, ultrasonic significantly improved the quality of puffed cowhide. Ultrasonic was used to treat the puffed cowhide at 210°C, at which the highest expansion rate, L*, and sensory acceptability are obtained. At this temperature, hardness, and masticatory properties obtained the minimum values. Moreover, the product's microstructure showed uniform bubbles, and the overall acceptability was high, thereby resulting in the optimal quality of the product. In addition, puffing rate and sensory evaluation were negatively correlated with hardness and chewiness, and the sensory evaluation was positively correlated with L*, ΔE, and puffing rate. Therefore, ultrasonic is an effective method for improving the quality of puffed cowhide. PRACTICAL APPLICATIONS: Ultrasonic processing is increasingly used in food technology. Through ultrasonic treatment, this study successfully solved the low expansion rate and poor coloration in puffed cowhide and found that cowhide can be recycled after slaughter. Ultrasonic‐treated puffed products exhibit bright color, high expansion rate, reduced hardness, and favorable chewiness and contain collagen that promotes health. These findings demonstrated that ultrasonic treatment significantly improves the quality of puffed cowhide.

This study investigated the activity of adenosine monophosphate-activated protein kinase (AMPK), glycolysis, and meat quality index in three altitude bovines during postmortem aging process. Local cattle (altitude:1,500 m), Gannan yak (3,000 m), and Yushu yak (4,500 m) postmortem Longissimus Dorsi (LD) muscle were used. Results indicated that CaCl2 significantly increased the AMPK activity by increasing the calcium-regulated protein kinase kinase (CaMKKβ) activity. Besides, AMPK activation enhanced the activity of lactate dehydrogenase (LDH) and Ca2+ -ATPase and accelerated the rate of muscle maturation during postmortem aging. Moreover, the expression of HIF-1, PRKAA2, and GLUT4 genes in high-altitude Yushu yak was higher than that of low-altitude bovines. CaCl2 activates AMPK by activating CaMKKβ cascade and accelerates postmortem glycolysis affecting the intramuscular environment, color, and muscle protein degradation to accelerate postmortem muscle maturation, suggesting that AMPK has essential effects on postmortem muscle glycolysis and quality, and can regulate muscle quality by regulating postmortem muscle AMPK activity. PRACTICAL APPLICATIONS: Insufficient postmortem glycolysis usually leads to DFD (dark, firm, and dry) meat. Beef have relatively high incidences of DFD meat, which has an unattractive dark color and causes significant loss to the meat industry. Therefore, AMPK, which can regulate postmortem glycolysis to affect meat quality, is a valid research target.