Comparison of bactericidal effects of two types of pilot-scale intense-pulsed-light devices on cassia seeds and glutinous millet

The aim of this study was to evaluate the bactericidal effect of two types of pilot-scale intense pulsed light (IPL) devices constructed in our laboratory. Cassia seeds and glutinous millet, with initial microbial loads of 2.04 × 104 and 5.03 × 103 CFU/g, respectively, were treated by cyclone-type and belt-type IPL devices at total fluences of 3.89-54.43 J/cm2. The maximum microbial reductions of the cassia seeds and glutinous millet were 0.74, and 0.66 log/g, respectively, when using the cyclone-type IPL, and 2.63 and 0.55 log/g when using the belt-type IPL device. The geometric mean diameter of cassia seeds and glutinous millet was 0.25 and 0.13, respectively. The cassia seeds having larger particle size than glutinous millet showed a greater bactericidal effect when treated with the belt-type device. Therefore, the design of the treatment chamber can have an improved bactericidal effect on cassia seeds, demonstrating the importance of selecting a suitable IPL device according to the size of the sample to be treated.