SUMMARYTenderness of roasted and stewed pectoralis major and biceps femoris muscles (estimated by shear values) from White Leghorn female birds was studied in relation to maturity and composition at 4, 8, 12 and 18 months of age. Shear values of pectoralis major muscles did not change significantly with age or differ significantly between cooking methods. Shear values of biceps femoris muscles increased significantly with age of roasted specimens. No similar significant change occurred in stewed specimens. Roasted biceps femoris had significantly higher (P<0.01) shear values than stewed samples at 12 months and more markedly at 18 months of age. No association was noticed between either intramuscular fat or moisture content and shear value trends. Hydroxyproline content (HOP) was determined in biceps femoris samples only. Total HOP content was significantly higher in more mature samples with a significant difference only at 12 months of age between cooking methods. Residual HOP content as a measure of collagen not converted to gelatin during cooking, showed a tendency to increase with age and differed significantly between cooking method only at 18 months of age. Total and residual HOP content of roasted biceps femoris were significantly correlated with shear values (r = 0.64 and 0.79, P<0.01). The marked increase in residual HOP content at 18 months seemed to explain more satisfactorily the divergence in shear values.
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