In this work, we compared the effects of carbon dioxide (CO₂) stunning, electric shock and non-stunning (direct slaughter) on the meat quality of yellow-feathered broilers (90 days old). The results showed that the degree of carcass injury in the CO₂ stunning group was the smallest, the rigor mortis process of muscle was shortened, the amount of bleeding was increased, and the rate of pH decline was significantly faster than that in the other two groups (P < 0.05). At 45 min postmortem, the brightness value (L*), redness value (a*) and yellowness value (b*) of the CO₂ stunning group were significantly lower than those of the other two groups (P < 0.05), while a significant increase in L* was found at 24 h (P < 0.05). At 45 min postmortem, the water-holding capacity, tenderness and texture (springiness and chewiness) of the CO₂ stunning group were significantly better than those of the other groups (P < 0.05), whereas the water-holding capacity and texture were significantly poorer at 24 h (P < 0.05). At 24 h, the sensory scores for odor and texture of the electric shock and direct slaughter groups were significantly higher than those of the CO₂ stunning group (P < 0.05). Collectively, CO₂ stunning is not be recommended for the slaughter of yellow-feathered broilers, and It is recommended to further optimize the mode of electric shock.

The changes in the pH, color, total bacterial count (TBC), total volatile basic nitrogen (TVB-N) content, malondialdehyde (MDA) content, sensory evaluation, and freshness (K value) of the breast muscle of yellow feathered broilers were measured during postmortem storage at 4 ℃. The results showed that according to pH and TBC, chicken breast meat samples stored for 0-3 and more than 3 days were identified as being fresh (pH < 6.7 and TBC < 6 (lg (CFU/g)) and stale (pH > 6.7 and TBC > 6 (lg (CFU/g)). According to sensory scores, the freshness of chicken breast meat stored for 0-4 and more than 4 days was acceptable (total sensory score > 60.00) and unacceptable (total sensory score < 60.00), respectively. According to K value, the corresponding time of the freshness of chicken breast meat was the day of slaughter (< 5%), as well as 1 (5%-15%), 2 (15%-20%), 3 (20%-25%), 4 (25%-30%), and 5 d (> 30%) after slaughter, and was graded into first, second, third, fourth, fifth grades of fresh and spoilage, respectively. Therefore, pH, TBC, sensory score and K value can reflect the freshness of chicken breast meat under short-term storage (within 5 days). The findings of this study can help determine the post-slaughter storage time and predict the shelf life of chicken breast meat.