Abstract: The Longissimus dorsi muscle of sheep was treated at different times postmortem with dielectric barrier discharge (DBD) low temperature plasma and evaluated for pH, total number of bacteria, myofibrillar fragmentation index (MFI) and myofibril ultrastructure during postmortem storage. Our aim was to determine the effects of DBD low temperature plasma treatment at different times after slaughter on mutton tenderness. The results showed that after 12 h of postmortem storage, the pH of mutton treated with DBD low-temperature plasma at 6 and 12 h postmortem was significantly lower than that of the other treated groups (P < 0.05); the total number of bacteria in mutton treated at 12–72 h after slaughter decreased significantly compared with the untreated group. As the storage time increased, MFI gradually increased, showed a significant upward trend during 6–72 h (P < 0.05), and then tended to be stable after 72 h for all treated groups. DBD low temperature plasma treatment at 6–24 h postmortem significantly increased the growth rate of MFI than the other treatments (P < 0.05). After 24 h storage, the sarcomere length of mutton treated at the early postmortem stage (6–24 h) was significantly reduced and shorter than that of the other treated groups (P < 0.05), and the sarcomere length of mutton in the 24 h postmortem treatment group was the shortest. In conclusion, DBD low-temperature plasma treatment at 12 to 24 h postmortem had the least effect on the tenderness of mutton while reducing the number of bacteria.

Key words: dielectric barrier discharge low temperature plasma; mutton; refrigerated storage; tenderness