UBC Theses and Dissertations
Textural and color responses of chicken muscle to substerilizing doses of gamma irradiation Whiting, Richard Charles,
The Pectoralis major and Pectoralis minor muscles of chicken were given substerilizing doses of ɤ-irradiation at varying times post-slaughter and the pH, shear force, fragmentation, and color were evaluated. pH measurements in an iodoacetate slurry showed that doses up to 300,000 rads administered at ⅕ or 5 hours post-mortem had no effect on either rate of pH fall or final pH. Irradiation at 2, 5t or 12 hours did not change the final pH taken at 48 hours post-mortem. Excised P. major muscles cooked by boiling between aluminium plates required more shear force at the posterior portion than at the anterior. Irradiation dose levels from 30,000 to 300,000 rads on P. major increased shear resistance over unirradiated muscles. The earlier the time of application (2, 5 and 12 hours post-slaughter) the greater the increase in toughness when measured at 60 hours post-slaughter. The 300,000 rad dose at 12 hours, given after attainment of maximum inextensibility and relaxation of isometric tension, still produced a significant loss in tenderness. The irradiation generally reduced the degree of myofibrillar fragmentation after a standardized blending treatment, although the decrease was not always significant. Pasteurizing irradiation produced a pink color in raw muscle stored aerobically for 55 hours that increased with dose. Peaks typical of an oxymyoglobin-like compound emerged and the dominant wavelength was shifted toward longer wavelengths by 4 nm. After cooking there was no visible color difference between irradiated and control muscles. Correlations between these parameters on control muscles indicated that the pH decline was positively correlated to shear force, although not of high value. The fragmentation ratios were not significantly correlated with shear force.