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. / Land and Food Systems, Faculty of / Graduate

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Experiments were conducted to investigate the effects of dietary fat, vitamin E(Vit. E) and selenium(Se) supplementation on the performance, fatty acid(FA) composition, lipid oxidation on blood and the oxidative stability of muscle tissues (breast and thigh) during refrigerated storage of broiler chickens fed high levels of flaxseed(FXS). Four hundred and eighty d-old broiler chicks were fed experimental diets for a 3 wk period, which consisted of the combination of two dietary fat sources: fullfat soybean(FFSB) and FXS; 3 Vit. E levels: 10, 40 and 80 IU/kg and two Se levels: 0.15 and 0.30ppm (Exp. I). Four hundred and forty d-old chicks were fed on FFSB diets supplemented with 10, 80, and 160 IU of Vit. E/kg, FXS diets supplemented with 10, 40, 80, 120, 160 and 200 IU of Vit. E/kg, corn-soybean based diet (control), and on a commercial diet for 21 days (Exp. II). For Exp. III, 1680 (840 of each sex) d-old broiler chicks were raised up to 41d. Three basal diets containing 10% FXS and 3 levels of Vit. E: 60-, 90- and 160 IU/kg were formulated for 3 age periods: starter (0--3wk), grower (3--5 wk) and finisher (5--6wk). Three groups of birds were fed these basal diets, while 3 other groups were fed the diet containing 160 IU of Vit. E either during the starter, grower or finisher phase (diets supplemented with 60 IU/kg were given in the two remaining phases). (Abstract shortened by UMI.)

Salmonella enteritidis has recently emerged as a potential pathogen in poultry products. The growth of S. enteritidis in poultry is affected by several factors such as storage temperature, pH, water activity, modified atmosphere and the presence of preservatives. All of these factors may act alone or in combination with each other resulting in a synergistic, antimicrobial effect. / In this research, initial storage studies were done to determine the effect of various atmospheres (air, vacuum, oxygen absorbent and gas packaging) on the microbial changes of packaged chicken thighs followed by challenge studies with a strain of S. enteritidis$ sp{ rm{NAST}}$. Chicken thighs were packaged in Cryovac bags and stored at 4 and 12$ sp circ$C for up to 28d. Changes in headspace gas composition, pH, drip loss, color and odor were monitored at each sampling day. / The effect of various packaging treatments, dipping solutions (chitosan (0.2%w/v) and potassium sorbate (0.2%w/v)) and low dose irradiation (1.5 & 3.0 kGy) on the growth of S. enteritidis$ sp{ rm NAST}$ and on the shelf-life of chicken thighs stored at 4 and 12$ sp circ$C was also investigated. (Abstract shortened by UMI.)

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