Influence of ultimate pH, sarcomere length and cooking loss on the textural variability of cookedM. pectoralis majorfrom free range and standard broilers

Abstract

1. An experiment was conducted to quantify the extent of variability in the texture of cooked poultry breast meat and to attempt to identify which intrinsic and extrinsic factors contribute to this. 2. Free range (FR) and standard (STD) broilers were killed and processed under commercial conditions and the M. pectoralis major muscle assessed for ultimate pH (pH(u)), sarcomere length, cooking loss and texture 24 h and 7 d after slaughter. . 3. Although FR broilers were females with an average age of 60 d, whereas the STD broilers were 45 d old and predominantly male, there were no significant differences in mean values obtained for pH(u), sarcomere length, cooking loss and shear force results between the two bird types. 4. While aging for 7 d increased the pH(u) and cooking loss means, sarcomere length means remained unchanged and shear force values decreased by 6% and 9% for FR and STD birds respectively. 5. Variability in shear force values also decreased on aging for 7 d, no birds having values above 4 kg/cm2 on day 7 whereas 16% were above this value on day 1. 6. There were significant correlations between the results for shear force, pH(u) and sarcomere length, indicating that increased shear force values were associated with a decrease in both pH(u) and sarcomere length. 7. These correlations suggest that variability in the texture of cooked M. pectoralis major from FR and STD chickens is strongly influenced by those post-mortem biochemical changes which lead to the development of rigor during the early stages of processing.