The evaluation of physical dimension changes as non-destructive measurements for monitoring rigor mortis development in broiler muscles

Abstract

Studies were conducted to develop a non-destructive method for monitoring the rate of rigor mortis development in poultry and to evaluate the effectiveness of electrical stimulation (ES). In the first study, 36 male broilers in each of two trials were processed at seven weeks of age. Half of the birds received electrical stimulation (400-450 V, 400-450 mA, 2 s on/1 s off for seven pulses) following bleeding while the other half were designated as controls. At 0.25 h and 1.5 h post-mortem (PM), carcasses were evaluated for the angles of the shoulder, elbow, and wing tip, and the distance between the elbows. Breast fillets were harvested at 1.5 h PM (after chilling) from all carcasses. Fillets were held on ice while the tips were excised and frozen for later measurement of pH and r-value. Shear value and pH means were significantly lower while R-value means were higher (P<0.05) for the ES fillets compared to the controls, suggesting the acceleration of rigor mortis by ES. Physical dimensions changed (P<0.05) during rigor mortis development and with ES. These results indicate that physical measurements of the wings may be useful as a non-destructive indicator of rigor development, and for monitoring the effectiveness of ES. In the second study, 60 male broilers in each of two trials were processed at seven weeks of age. At 0.25 h, 1.5 h, 3.0 h, and 6.0 h PM, carcasses were evaluated for the distance between the elbows. At each time point, breast fillets were harvested from each carcass. Fillets were held on ice while the tips were excised and frozen for later measurement of pH and sarcomere length. Shear value and pH means (P<0.05) decreased while sarcomere length means (P<0.05) increased over time, suggesting an overall increase in rigor development. Elbow distance decreased (P<0.05) with rigor development and was correlated (P<0.01) with shear value (r= 0.2581), sarcomere length (r= -0.3079), and pH (r= 0.6303). These results suggest that elbow distance could be used in conjunction with other detection methods for optically automating the measurement of rigor mortis development in broiler carcasses.