Effects of different medium-voltage electrical stimulation (ES) and ageing on postmortem changes in longissimus dorsi muscle of the fat-tailed sheep were studied. Fifteen male animals were divided into 5 equal groups (n = 3) including: T1 (control, without ES), T2 (100 V/30 s), T3 (100 V/60 s), T4 (150 V/30 s), and T5 (150 V/60 s) with fixed frequency of 50 Hz. Five minutes after sticking, the carcasses were stimulated in order of the treatments. After normal processing, they were kept at 6 ◦C for 14 d. ES accelerated the glycolytic rate resulting in a significant fast fall in pH (P < 0.05) during the 1st 6-h postmortem (PM) with a gradual decline until 24-h PM, and a simultaneous significant reduction in adenosine triphosphate (ATP) content (P < 0.05). There was a significant (P < 0.05) decline in the total calpain activity during the 1st 6-h PM. The muscles from ES carcasses had significantly (P < 0.05) lower water holding capacity (WHC) than those from nonstimulated ones. Ageing revealed a significant (P < 0.05) effect on the reduction of WHC. No significant difference was found for the mean value of the muscle color (L∗, a∗, and b∗) in all treatment groups during ageing (P > 0.05). The results of free amino acid (FAA) content and myofibrillar fragmentation index (MFI) revealed a significant improvement of proteolysis and tenderness by ES and ageing (P < 0.05). In the present study, higher voltage/duration (150 V/60 s) showed greater effects and significantly accelerated glycolysis, pH decline, and ATP depletion and thus decreased the time for rigor completion and improved the tenderness
کلید واژگان :calpain, electrical stimulation, fat-tailed sheep, tenderness, water holding capacity
ارزش ریالی : 600000 ریال
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