Gaseous Ozone Distribution Within a Forced Air Ozone Reactor for Bulk Produce Decontamination
Recalls of fresh produce due to possible bacterial contamination are increasing. Commonly used disinfection methods such as washing in chlorinated water can impact food quality and often have limited effectiveness. Recently, an Ontario food-processing company has designed and built a fresh produce decontamination treatment system that fumigates bulk produce within a forced air ozone reactor with low concentrations of gaseous ozone. Prior trials demonstrated that a 2-log reduction of a Listeria surrogate could be achieved throughout a 500 kg batch of apples using the reactor although the distribution of ozone through the produce bed is unknown. The current study was undertaken to gain a better understanding of the ozone transport and flow dynamics within the reactor. Measurements of ozone concentrations, air flow rates, pressure, temperatures, and humidity were collected and recorded during system operation to characterize the system pressure losses, thermal characteristics and operating treatment conditions. It is concluded that a balance between superficial air velocity and initial ozone concentration is required to minimize pressure drops (energy cost) while maintaining well distributed airflow throughout the bed and to achieve desired microbial reduction. The data generated will enable the reactor design to be further optimized and applied to decontaminating a diverse range of produce type.