In order to examine microbial decontamination by UV-C treatment of strawberries on a continuously moving conveyor, we developed a three-dimensional irradiation model based on a discrete ordinates (DO) method to evaluate UV-C dose distribution on strawberries. The sliding mesh method was employed to describe the motion of strawberries placed on a UV-C-transparent film tray on a conveyor through a UV-C treatment system. We also estimated total UV-C radiation dose distribution on the surface of strawberries for four different configurations. The models with four lamps installed in parallel to the direction of movement provided uniform dose distribution. The time required for three-log inactivation of Penicillium digitatum on the surface of strawberries was also calculated. For the optimal model (Model D), 131 s was required for three-log inactivation of P. digitatum. The proposed radiation model was shown to be a useful tool for the optimization of UV-C treatment for strawberry.
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