Effects of different irradiation doses and storage period on microbiological characteristics of wheat (Triticum aestivum L.)

Microbiological analysis of wheat (Triticum aestivum L.) treated with different doses of ionizing radiation (0.2 kGy, 0.5 kGy, 1 kGy, 5 kGy and 10 kGy) is presented in this paper. The aim was to determine the influence of different irradiation doses on the microbial population profile of wheat. In all samples, the total bacterial count and the populations of Enterobacteriaceae, Escherichia coli, Salmonella spp, coagulase-positive Staphylococci, Pseudomonas aeruginosa, Bacillus cereus, Clostridium perfringens, yeasts and molds were examined. The analyses were carried out twice: immediately after irradiation and nine months after treatment. Obtained results revealed the presence of Bacillus cereus, Enterobacteriaceae, yeasts and molds in all examined samples. Salmonella spp, Pseudomonas aeruginosa, Escherichia coli and Clostridium perfringens, were not detected. It has been found that the number of microorganisms decreases with the increase in the irradiation dose, with no viable microorganisms detected at the dose of 10 kGy. In all examined samples, nine months after irradiation, there was a noticeable reduction in the number of microorganisms. Only yeasts and molds were detected at a dose of 5 kGy, while no microbial growth was observed at 10 kGy. There are no reference studies on Enterobacteriaceae inactivation in wheat by ionizing radiation and storage. Therefore this study is the first contribution to understanding this microbial community decrease by gamma radiation after room temperature storage. The results highlighted the prolonged effect of ionizing radiation treatment on the microbiological safety of wheat.