Development and evaluation of a fluidized bed system for wheat grain disinfection

Durum wheat grain from the field is naturally contaminated with bacteria, yeast, and mold. The reduction in aerobic plate count (APC) and yeast and mold count (YMC) is often necessary before processing wheat. Gaseous ozone, ozonated water, and acetic acid solution are nontraditional antimicrobial agents for grains and are safe for humans and the environment. Better disinfection may be possible by applying antimicrobial agents to grain in a fluidized state. Fluidization increases the exposure of grain surfaces, resulting in uniform and quick contact of grain with antimicrobial agents. Therefore, a fluidized bed was developed with automated spraying system (to spray treatment waters), and a port for gaseous ozone injection. The pressures and velocities within the fluidized bed system were measured to characterize the system. The treatments used on fluidized grain were: distilled water (control), gaseous ozone (6 ppm), ozonated water (23 mg/L), gaseous ozone + ozonated water (6 ppm, 23 mg/L), acetic acid solution (0.5%), acetic acid + ozonated water (0.5%, 26 mg/L), and gaseous ozone + acetic acid + ozonated water (6 ppm, 0.5%, 26 mg/L). The last of these treatments was most effective with 1.7 and 3.3 log reduction in APC and YMC, respectively. This combined treatment can be used to replace the chlorinated water that industry uses during tempering of grain. Ozonated water alone resulted in a 0.3 log reduction in both APC and YMC. Gaseous ozone alone did not cause a significant reduction in APC and YMC.