Abstract: Horse carcasses were subjected to different durations of electrical stimulation after slaughter and the cooking loss, shear force, soluble protein concentration (SPC), myofibrillar fragmentation index (MFI), collagen solubility and muscle fiber microstructure in horsemeat were assayed during postmortem aging. The results indicated that electrical stimulation had no significant impact on the cooking loss of horsemeat during aging (P > 0.05). However, within a certain range of electrical stimulation duration, the shear force decreased, whereas SPC, MFI and collagen solubility increased during aging. Under the experimental conditions used in this study, electrical stimulation for 60 s improved the tenderness of horsemeat, but this effect was not enhanced by increasing the treatment time. Electrical stimulation for 60 s decreased the shear force of horsemeat at 14 d of aging by 13.8% and increased SPC and MFI 1.16- and 1.28- fold, respectively as compared with the control. Moreover, this treatment destroyed muscle fiber microstructure. In summary, appropriate electrical stimulation promoted postmortem aging of horsemeat and improved meat tenderness. This study will provide theoretical insights into the mechanism of meat tenderization by electrical stimulation and a theoretical basis for new product development.

Key words: electrical stimulation, horsemeat, aging, tenderness