A multiscale Monte Carlo simulation of irradiating a typical-size apple by low-energy X-rays and electron beams

Irradiation of foods and fruits by ionizing radiation effectively eliminates pathogenic microorganisms primarily present on the surface. Recently, much attention has been paid to the use of low-energy X-rays and electron beams for food irradiation. Dosimetric investigation of foods with complex shapes is experimentally challenging. In this study, a multiscale Monte Carlo simulation was performed to compare the dose distributions of low-energy X-rays and electrons in a typical-size apple as well as to calculate the DNA damages induced by secondary electrons in a bacterial cell model. Several energies up to 500 keV and tube voltages up to 200 kV were considered for incident electrons and X-rays, respectively. The results indicate that on a microscopic scale, the yields of single- and double-stranded DNA breaks induced by X-rays and electrons of different energies are nearly identical. In a macroscopic scale, a two-sided electron beam configuration plus a 90-degree rotation of the apple (or the beam) provides an appropriate dose uniformity on the apple surface up to a depth of 40 μm. In the case of low-energy X-rays, apple rotation is not required when a two-sided irradiation is applied. Generally, X-rays are superior to electrons for the surface treatment of apples due to their lower dose uniformity ratios on the surface.