Relationship between Mitochondrial Damage and Meat Tenderness of Tan Sheep during Postmortem Aging

This research investigated the relationship between mitochondrial damage and meat tenderness of Tan sheep during postmortem aging. The M. Longissimus dorsi muscles from six-month-old Tan sheep were divided into lipopolysaccharide (LPS) treatment and blank control groups. Mitochondrial reactive oxygen species (ROS) content, membrane potential, mitochondrial permeability transition pore (MPTP) openness, mitochondrial swelling, pH, cooking loss, texture, moisture distribution, shear force and myofibril fragmentation index (MFI) in each group were measured at 0, 6, 12, 24, and 72 hours postmortem. The results showed that during postmortem aging, MPTP openness gradually increased in both groups. ROS content, cooking loss rate and MFI value showed an increasing trend as well. Mitochondrial membrane potential, pH, elasticity, T₂₂ peak area and shear force showed a decreasing trend. Hardness, chewability and cohesiveness increased at first and then decreased. Therefore, disruption of oxidative homeostasis in muscle cells of Tan sheep resulted in an increase of ROS content, which caused mitochondrial damage by inducing the opening of MPTP and decreasing mitochondrial membrane potential. Moreover, the structural changes of myofibrils shortened the gap between muscle protein molecules, resulting in increased water loss rate and poorer water retention in muscles, promoting the process of myofibril fragmentation and improving the tenderness of Tan sheep meat. Correlation analysis showed that mitochondrial damage and tenderization occurred simultaneously during the postmortem aging of Tan sheep meat, and the more serious the mitochondrial damage was, the better the tenderness was.