Variations in Muscle Chemical Composition, pH, and Protein Extractability Among Eight Different Broiler Crosses

Abstract

Variations in muscle chemical composition, pH, and protein extractability were studied using male broilers of eight different genetic crosses of commercial strains. Three replicate groups of 24 birds of each cross were grown in floor pens using commercial corn-soybean meal diets. At 8 wk of age, three birds per replicate, weighing within 5% of the pen average, were slaughtered, scalded, defeathered, eviscerated, and chilled in ice slurries overnight. Muscles were excised from breasts and thighs, and trimmed of skin and external fat. Proximate analysis was conducted using ground muscle pooled within replicate groups. Breast muscle of all strain crosses contained more (P ≤ .05) total protein (ranging from 20.7 to 23.6%) and moisture (74.6 to 75.9%), and less fat (1.0 to 2.0%) than thigh muscle, which contained 18.1 to 21.3% protein, 72.8 to 73.8% moisture, and 5.0 to 7.2% fat. The pH of breast muscle was lower (P ≤ .05) than that of thigh muscle for four of the eight strains, and protein extractability of breast muscle was greater (P ≤ .05) than that of thigh muscle for all strains. There were significant differences among strains in chemical composition, pH, and protein extractability for both breast and thigh muscles. The correlation between percentage protein and fat was positive in breast (r = .72, P < .05) and negative in thigh muscle (r = −.77, P < .05). However, no significant correlations were observed between the chemical constituents of breast muscle with the respective constituents of thigh muscle. The results revealed considerable differences in muscle composition, pH, and protein extractability as influenced by genetic strain and muscle type.