Abstract:

Objective: To explore the effect of electrical stimulation on shear force, MFI and myofibrillar microstructure ofyak during postmortem aging. Methods: Twenty black yaks from the South of China’s Gansu province were selected anddivided into 4 groups with 5 yaks each. After slaughter, the carcasses were subjected to electrical stimulation (ES) at 21 Vand 50 W for 72, 90 or 108 s and subsequent chilling as ESC, or normal chilling alone (0–4 ℃ and 0.5 m/s air velocity)as a control. At 0,1, 3, 5, 7 and 9 days postmortem, the shear force, myofibril fragmentation index (MFI) and myofibrillarmicrostructure were determined. Results: Electrical stimulation accelerated the decrease in shear force. At 0 d postmortem,the shear force of ESC108 s was higher than all other treatments. The average shear force of ESC 72, 90 and 108 s was12.9%, 17.9% and 5.9% lower than that of NC at 9 days, respectively. At 0 d postmortem, the MFI of ESC 90 s was thehighest of all treatments. At 9 days postmortem, the MFI values of ESC 72 and 90 s were 7.71% and 9.86% higher thanthat of NC. The MFI of yak meat was very significantly correlated with the shear force, implying the close associationbetween meat tenderness and myofiber degradation. The length of sarcomeres was significantly shortened as a result ofelectrical stimulation, and the myofiber diameters of ESC 72, 90 and 108 s were respectively 57.47%, 68.97% and 80.46%as compared to NC. As a result, 47% myofiber was degraded. Conclusion: Electrical stimulation can improve the tendernessof yak, shorten the aging time and damage the structure of myofiber.

Key words: yak, electrical stimulation, chilling, aging, tenderness