Thesis (Ph.D.) - Cairo University - National Institute of Laser Enhanced Sciences - Department of Laser Applications in Biotechnology

The conceptual framework and the objectives of this study were to get a better understanding of the effect of gamma, ultraviolet (UV) radiation and laser exposure on the fresh beef quality during cold storage at 4+1oC with respect to survival and growth of bacteria, shelf-life, physiochemical and color properties of the the fresh beef. Fresh beef was exposed to three doses 2.5, 5 and 7 kGy of gamma radiation, 12.7, 25.5 and 38.2 W.s/cm2 of ultraviolet (254 nm) and 9, 18 and 27 W.s/cm2 of visible blue laser beam with wavelength (450 nm). The obtained results were as following: 1) The gamma radiation was leaded to reduce the total count of bacteria in the beef samples of (3.7x105, 2.8x103, 7.4x10 and less than 10 CFU/g) for control, 2.5, 5 and 7 kGy respectively. Moreover, the shelf lives of the gamma irradiated beef samples were considerably of (10, 20 and 40 days) for 2.5, 5 and 7 kGy, respectively. The percentages of the gamma irradiated beef samples were decreasing of (79.17, 78.94, 78.64 and 78.53%), (20.61, 19.63, 19.41 and 18.95%), (2.86, 2.11, 2.01 and 1.9%) and (2.98, 2.74, 2.6 and 2.56%) at moisture content, protein, collagen and fat, respectively. Whereas there were increasing of (5.92, 5.86, 5.97 and 5.69) and (0.71, 0.91, 1.3 and 1.5 mg malonaldehyde/1kg beef sample) at pH and TBA values, respectively for control, 2.5, 5 and 7 kGy, respectively.The physical parameters of beef samples were slightly decreasing of (47.11, 46.67, 43.14 and 42.02%) and (78.81, 75.01, 74.53 and 73.81%) at cooking loss and water holding capacity, respectively; while there were increasing of (1.84, 1.94, 2.14 and 2.36 kgf) at share force by gamma radiation for control, 2.5, 5 and 7 kGy doses, respectively. Gamma irradiated beef samples had higher values of (30.64, 30.76, 31.76 and 32.12) and (24.56 to 26.63, 27.37 and 29.77 degree) at saturation values and Hue degrees, respectively; while it had lower lightness values of (35.69, 34.87, 34.66 and 33.66) for control, 2.5, 5 and 7 kGy doses, respectively

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