Browsing by Subject "food irradiation"
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Item Dose calculation methodology for irradiation treatment of complex-shaped foods(2009-06-02) Kim, JongsoonDose calculation methodology was developed for irradiation treatment of complex-shaped foods. To obtain satisfactory electron beam irradiation of food products, a strict process control is required to ensure that the dose delivered to all parts of the treated product falls within some specified range. The Monte Carlo electron transport simulation and computer tomography (CT) scan technology were used to predict the dose distribution in complex shaped foods, an apple phantom composed of paraffin wax, chloroform, and methyl yellow, and a chicken carcass. The Monte Carlo code used was successfully tested against the experimental data, resulting in less than 5% discrepancy between the simulated and measured data. For 1.35 MeV electron beam simulation of apple phantom, tilting and axial rotation ensures dose distribution of the entire surface of the phantom, even reaching the critical regions of the apple stem and calyx ends. For 1 and 5 MeV X-ray simulations, both depth-dose curves show exponential attenuation after a build-up region. The depth to peak for the former is shorter than that of the latter. For 1.35 MeV electron beam simulation of a chicken carcass, dose adsorption occurred up to 5-7 mm deep, resulting in surface irradiation of the carcass. For 10 MeV electron beam simulation, the doses within the carcass reached a peak of 1.2 times the incident dose with increasing depth. Two-sided X-ray (5 MeV) irradiation significantly improved the dose uniformity ratio, from 2.5 to 1.8. A web-based integrated system was developed for data manipulation and management for irradiation treatment of foods. Based on CT scan, three dimensional geometry modeling was used to provide input data to the general Monte Carlo N-Particle (MCNP) code. A web-based interface provided the on-line capability to formulate input data for MCNP and to visualize output data generated by MCNP. The integrated Matlab and Matlab Web Server programs automatically functions through the steps and procedures for data input and output during simulation. In addition, a database having D10 values (decimal reduction value), food nutrition composition, and qualities was integrated into the dose planning system to support food irradiation treatment.Item Radiosensitization Strategies for Enhanced E-beam Irradiation Treatment of Fresh Produce(2011-08-08) Gomes, CarmenFresh produce is increasingly implicated in outbreaks of foodborne illness. Internalization of bacterial pathogens into produce is of particular concern as internalized pathogens are unlikely to be removed by surface sanitizers. It is therefore necessary to develop treatments that will reduce their prevalence and numbers on fresh produce. Irradiation is a penetrating nonthermal treatment that effectively eliminates bacteria. Irradiated baby spinach leaves up to 1.0 kGy showed negligible (P>0.05) changes in color, texture, vitamin C, total carotenoids, and chlorophyll content compared to non-irradiated controls throughout storage (15 days at 4oC). This research also shows that irradiation effectively reduces viable Escherichia coli cells internalized in lettuce, and that decontamination is not influenced (P>0.05) by lettuce variety. Irradiation effectively reduced the population of internalized pathogens in a dose-dependent manner (3-4 log reduction at 1.0 kGy). Microscopy images suggest that the contamination sites of pathogens in leafy vegetables are mainly localized on crevices and in the stomata. A careful design of the treatment (understanding dose distribution) will effectively eliminate pathogens while maintaining produce quality. The use of modified atmosphere packaging increased (P<0.05) the sensitivity of pathogens (Salmonella spp. and Listeria spp.) to irradiation in baby spinach leaves (up to 25%). Increasing concentration of oxygen increased (P<0.05) sensitivity of both microorganisms. Radiosensitization could be affected (P<0.05) by production of ozone, which increases with increasing dose-rate and oxygen concentration, and reducing temperatures. Antimicrobial effectiveness of various active compounds was determined against Salmonella spp. and Listeria spp. Inclusion complexes were prepared with antimicrobial compounds and -cyclodextrin. The effectiveness of the microencapsulated compounds was tested by spraying them on the surface of baby spinach leaves inoculated with Salmonella spp. The increase in radiosensitivity (up to 40%) varied with the antimicrobial compound. Spherical poly (DL-lactide-co-glycolide) (PLGA) nanoparticles with entrapped eugenol and trans-cinnamaldehyde were synthesized for future antimicrobial delivery applications. All loaded nanoparticles proved to be efficient in inhibiting growth of Salmonella spp. and Listeria spp. The entrapment efficiency for eugenol and trans-cinnamaldehyde was 98% and 92%, respectively. Controlled release experiments (in vitro at 37oC for 72 hrs) showed an initial burst followed by a slower release rate of the antimicrobial entrapped inside the PLGA matrix.