Browsing by Subject "Food Irradiation"
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Item A Theoretical Approach for the Determination and Mechanistic Interpretation of Radiation D10-value(2010-07-14) Ekpanyaskun, NontIn the design of the food irradiation process, the knowledge of the radiation resistance of the target organism in a specific food commodity is required. The D10-value, the radiation dose needed to inactivate 90% of the microbial load in the food medium, is used to relate the amount of absorbed energy to the surviving bacterial population. Numerous experimental studies have been performed to determine the D10 values of several food-borne microorganisms irradiated under various conditions. Nevertheless, accurate predictions of D10 values of the pathogens in food products that have not been empirically examined cannot be made due to insufficient understanding of the biological response to radiation exposure. A theoretical model for the derivation of the D10-value has been proposed in this study to mechanistically assess the production of radiation-induced DNA damage by energetic electrons. The step-by-step Monte-Carlo simulation technique, which employs the detailed histories of the ionizing particles and the radiolytic species, was utilized. The effects of selected parameters including the genomic sequence, the type of DNA double strand break, the DNA damaging agents, the radical scavengers, the degree of dispersion of DNA molecules, and the number of genome equivalents were hypothetically investigated. The developed computational methodology as well as the results presented can be used as an analytical tool to evaluate the impact of ionizing radiation on cell survival.Item Development of a chemical dosimeter for electron beam food irradiation(Texas A&M University, 2006-08-16) Rivadeneira, Ramiro GeovannyA chemical solution composed of paraffin wax, chloroform, and methyl yellow biological indicator was shaped into a solid 3-D apple phantom to determine absorbed dose from e-beams and X-rays. The purpose of this research was to determine the most uniform irradiation treatment on apple-phantoms (a complex shaped target) and GAFCHROMIC?? HD-810 films using electron beams from (1) a 2 MeV Van de Graaff (VDG) accelerator, (2) a 10 MeV Linear Accelerator (LINAC), and (3) X-rays from a 5 MeV LINAC. Irradiation with the VDG accelerator confirmed that tilting the apple-phantom yaxis towards the e-beam source by 90 degrees, 45, and 22.5 degrees resulted in more uniform treatment in both the methyl yellow apple phantom and HD-810 film. The phantoms were over-exposed at the top and bottom regions when their y-axis was oriented exactly parallel to the e-beam at 22.5-degrees. The 45-degree orientation ensured uniformity throughout the whole apple surface without overexposing it at the top and bottom. In contrast, the 90-degree orientation resulted in the least effective treatment with the bottom and top region not receiving any radiation. A 10 MeV dual e-beam showed uniform penetration from top to bottom in the HD-810 film and apple phantoms. The HD-810 film responded linearly with doses up to 1.5 kGy while the methyl yellow response was non-linear up to 0.5 kGy maximum. The X-ray irradiation completely penetrated the apple phantoms from top to bottom showing excellent lateral uniformity at different penetration depths.