The role of histidine dipeptides on postmortem acidification of broiler muscles with different energy metabolism

It is generally held that the content of several free amino acids and dipeptides is closely related to the energy-supplying metabolism of skeletal muscles. Metabolic characteristics of muscles are involved in the variability of meat quality due to their ability to influence the patterns of energy metabolism not only in living animal but also during post-mortem time. Within this context, this study aimed at establishing whether the concentration of histidine dipeptides can affect muscle post-mortem metabolism, examining the glycolytic pathway of three chicken muscles (Pectoralis major, extensor iliotibialis lateralis and gastrocnemius internus as glycolytic, intermediate and oxidative-type, respectively) selected based on their histidine dipeptides content and ultimate pH. Thus, a total of 8 carcasses were obtained from the same flock of broiler chickens (Ross 308 strain, females, 49 days of age, 2.8 kg body weight at slaughter) and selected immediately after evisceration from the line of a commercial processing plant. Meat samples of about 1 cm3 were excised from bone-in muscles at 15, 60, 120 and 1,440 min post-mortem, instantly frozen in liquid nitrogen and used for the determination of pH, glycolytic metabolites, buffering capacity as well as histidine dipeptides content through 1H-NMR. Overall results suggest that glycolysis in leg muscles ceased already after 2 h post-mortem, while in breast muscle continued until 24 h, when it exhibited significantly lower pH values (P<0.05). However, considering its remarkable glycolytic potential, Pectoralis major muscle should have exhibited a greater and faster acidification, suggesting that its higher (P<0.05) histidine dipeptides’ content might have prevented a potentially stronger acidification process. Accordingly, breast muscle also showed greater (P<0.05) buffering ability in the pH range 6.0-7.0. Therefore, anserine and carnosine, being highly positively correlated with muscle’s buffering capacity (P<0.001), might play a role in regulating post-mortem pH decline, thus exerting an effect on muscle metabolism during pre-rigor phase and the quality of the forthcoming meat. Overall results also suggest that total histidine dipeptides content along with muscular ultimate pH represent good indicators for the energy-supplying metabolism of chicken muscles.