Optimization modeling of fluid bed drying and coating technique to control fungal growth and aflatoxin content in paddy

Fluid bed drying with temperatures of 70-130 degrees C, together with a coating system based on a zinc oxide nanoparticle (n-ZnO) solution, was investigated for control of fungal growth in paddy before storage. A mathematical model to find suitable conditions for this process was developed. The installation of the coating system into the drying system was possible and the amount of n-ZnO in paddy, as detected by an X-ray diffractometer, related to the operating time. Total phenolic content decreased by 9.4% when a hot air temperature of 130 degrees C was used. The percentage of fungal growth decreased with an increase in hot air temperature and operating time. This decrease could be expressed by a first-order rate reaction. Specific energy consumption decreased to 72.5% as hot air temperature increased. The mathematical model could predict suitable process conditions to completely control fungal growth and aflatoxin content while maintaining total phenolic content. Novelty impact statement: Sangyod rice is a high-value variety of rice cultivated in Thailand, which is abundant in total phenolic content, including anthocyanins. However, since this species can only be cultivated once a year, the rice is stored in storehouses for long durations of time, where there is the risk of fungal infection. This study reports a novel coating method adapted for the fluid bed drying technique, and its optimization using both experiments and mathematical modeling. The data obtained from this research will have applications for the rice industry.

Automated summary

The combination of fluid bed drying and n-ZnO coating system proved to be effective in controlling fungal growth in paddy before storage. Mathematical modeling helped in predicting suitable conditions for the process, and the results showed that higher hot air temperature and longer operating time decreased fungal growth and phenolic content while reducing specific energy consumption. Novel coating method for Sangyod rice has potential application in the rice industry to safeguard against fungal infection during long-term storage.