Exudate Protein Composition and Meat Tenderness of Broiler Breast Fillets

The relationship between meat tenderness and the protein composition of muscle exudates collected from broiler breast fillets deboned at different postmortem times was investigated. A total of 85 broilers were processed and breast fillets from each carcass were deboned at either 2 h (early-deboned, EB) or 24 h (control) postmortem. One fillet per carcass was used for 1 d postmortem meat tenderness measurements and the other fillet was stored at 4°C until 6 d postmortem for the collection of exudate prior to tenderness evaluation. Protein content and composition of muscle exudates were determined by a biuret assay and SDS-PAGE. Fillet pH, color, drip loss, and cook loss were also measured. Early-deboned fillets exhibited greater (P < 0.05) Warner-Bratzler shear force (WBSF) than controls at 1 d (7.4 vs. 3.1 kg) and 6 d (4.1 vs. 2.5 kg). Deboning time did not influence pH or color values (L*a*b*). Control fillets exhibited less drip loss after 6 d of storage (P = 0.005) and less cook loss at 1 and 6 d (P < 0.001). Exudate protein concentration was not influenced by deboning time. From the SDS-PAGE profiles of the exudates, the relative abundances of seventeen protein bands were quantified. Electrophoresis analysis revealed that, in general, the protein profiles of exudates from control and EB fillets were not distinct from each other. However, the band corresponding to 225 kDa was more abundant in controls (P = 0.021). Although the protein concentrations and SDS-PAGE profiles of muscle exudates varied widely between breast fillets, variations in exudate protein characteristics were not strongly associated with changes in the tenderness of broiler breast meat due to the combined effects of postmortem deboning time and post-deboning aging.