Effects of Medium‐Voltage Electrical Stimulation on Postmortem Changes in Fat‐Tailed Sheep

Abstract

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.

Systematic studies on improving structural properties of myofibrillar proteins and pork quality based on electrical stimulation

“…During storage, a significantly higher storage loss and cooking loss were observed in the ES‐treated group than in the control group ( P < 0.05), which was consistent with the results of Abbasvali et al . (2012), reporting that ES reduced WHC in sheep meat. This might have happened because ES causes a strong contraction of the muscle fibres in the meat (Fig.…”

“…Alternatively, ES promotes glycolysis, causing a rapid drop in muscle pH. An increase in protein degradation results in severe protein denaturation, which disrupts the muscle cell structure and exposes more hydrophobic groups (Abbasvali et al., 2012), thus decreasing WHC. The difference in storage and cooking losses between the 0.5 and 1 A treatment groups was significant ( P < 0.05) in the early stages of storage; however, no significant difference was observed between the ES‐treated 0.5 and 1 A groups at 8 days storage time ( P > 0.05).…”

Endogenous Proteolytic Systems and Meat Tenderness: Influence of Post-Mortem Storage and Processing

“…Several studies have shown that electrical stimulation resulted in early activation of calpains, accelerated proteolysis of the muscle proteins and increased muscle tenderness in Longissimus dorsi muscle of fat-tailed sheep ( Abbasvali et al, 2012 ), and Longissimus lumborum muscle of cattle ( Ferguson et al, 2000 ; Li et al, 2012 ) and lamb ( Pouliot et al, 2014 ). However, Kim et al (2013) reported that tenderness and proteolysis of the Longissimus dorsi muscles from calves stimulated by low voltage remained unaffected.…”