Effect of different stunning methods on rigor mortis, shape, energetic status and physical characteristics of Salmo carpio fillets.

BACKGROUND: Consumer interest in safeguarding animal welfare and increased demand for fresh aquatic products support the need to understand the effects of stunning methods used in aquaculture on the biochemical process affecting fish fillet quality. The present paper aimed at comparing electrical stunning (ES) and cold shock (ICE) in Salmo carpio, an Italian endemic under-investigated species. Rigor mortis evolution, fillet adenosine 5'-triphosphate (ATP), shape, colour, pH and water holding capacity were assessed by integrating chemical and image analyses. RESULTS: Seventy-two fish (24 fish per treatment) were stunned by ES, ICE or anaesthesia (AN, used as control), then percussively slaughtered. ES and ICE hastened rigor mortis onset and resolution (21 and 28 h post mortem) compared to AN. This was confirmed by the faster ATP degradation in ES and ICE. Fillet shape features varied during rigor mortis, according to the stunning method, with the perimeter showing irreversible variation in ES and ICE groups. Initial circularity was recovered only in AN, while ICE and ES fillets showed significantly different values, between 0 and 192 h. CONCLUSION: ES is a promising stunning technique for S. carpio, but parameters should be optimized, because of the adverse effect on muscle activity which caused a fast pH drop, and the presence of blood spots in the fillets. Further studies are needed to understand whether fillet shape changes can interfere with filleting or fillet processing and consumer appreciation. © 2022 Society of Chemical Industry.

Effect of stunning amperage on broiler breast muscle rigor development and meat quality.

Two experiments were conducted to determine the effects of constant amperage (as opposed to constant voltage) electrical stunning on broiler blood loss, post-mortem breast muscle (Pectoralis major) rigor development, and breast meat quality. Broilers were individually stunned for 5 s at 0 (unstunned control group), 50, 100, 150, and 200 mA in Experiment 1 and at 0, 50, and 125 mA in Experiment 2. Breast muscle pH and R-value (ratio of adenosine to inosine nucleotides) were determined at 15 min and 24 h post-mortem; breast meat shear value and color were determined at 48 h post-mortem. Stunning amperage had no effect on percentage blood loss in either experiment. The most rapid post-mortem reactions were observed for the unstunned control group as determined by pH and R-value at 15 min post-mortem. Birds stunned with 50 mA were intermediate with regard to rate of rigor development. The slowest post-mortem reactions occurred in broilers stunned from 100 to 200 mA. There were no differences in pH, R-value, or color between stunning treatments after carcasses were aged for 24 h. Stunning amperage did not affect Allo-Kramer shear value for breast muscles deboned at 15 min post-mortem. In Experiment 2, 24 h aged breast meat from broilers stunned with 125 mA required significantly higher shear value (4.5 kg/g) than breast meat from broilers stunned at 0 or 50 mA (3.8 and 3.6 kg/g, respectively). Results indicate that stunning amperages between 0 and 200 mA had effects on the rate of early rigor development but there were no consistent effects on final breast meat quality.

Effect of electrical stunning amperage and peri-mortem struggle on broiler breast rigor development and meat quality.

Two experiments were conducted to determine the effects of electrical stunning and peri-mortem muscle activity (struggle in and around the time of slaughter) on post-mortem biochemical reactions in broiler breast muscle (Pectoralis major). Broilers were stunned with either 50 or 125 mA or were killed without stunning. In Experiment 1 (n = 273), broilers were either physically restrained to reduce struggling during slaughter or were unrestrained and allowed to struggle freely. Breast mean pH and R-value (ratio of adenosine to inosine nucleotides) were determined at 15 min and 24 h post-mortem, and Allo-Kramer shear was determined on 48 h post-mortem cooked meat samples from muscles excised at 15 min or 24 h. In Experiment 2 (n = 65), the breast muscle was unilaterally denervated by surgically severing the Pectoralis nerve on one side and performing a sham operation on the contralateral side. Results indicated that physical restraint resulted in higher muscle pH and lower R-values at 15 min post-mortem in the unstunned birds and birds stunned at 50 mA, but had no effect on breast meat from birds stunned at 125 mA. There were no treatment effects on meat tenderness or 24-h post-mortem pH or R-values. Stunning amperage had no effect on denervated muscle pH at 15 min post-mortem, but did affect the sham-operated muscle pH and R-values as in Experiment 1. These results indicate that the main effect of electrical stunning on early rigor development may be due primarily to inhibition of peri-mortem struggle.