The effect of temperature and microwave radiation on the behavior of pesticides during the drying of cereal grains

Final products may contain pesticides used for the protection of cereals. The drying process can either reduce or increase the concentration of pesticides. However, their behavior during grain drying is not fully described in the literature. The objective of this study was to assess the effect of physical factors, i.e. temperature and microwave radiation, on the behavior of pesticides most commonly used for the protection of cereals. Three matrices: spring wheat, winter rye, and spring barley, and six active substances of plant protection products were selected for the study. Field trials were carried out to acquire cereal material. The procedures used twice the recommended dose indicated on the label of the respective product. Four different drying variants were applied. Three of them allowed thorough monitoring of the behavior of pesticides for five successive days; Variant 4 included the effect of a physical factor, namely, microwave radiation. The drying process reduced the residues of six pesticides by 18 %-85 %. The effect of microwave radiation on the reduction of pesticides in cereal grains was the most effective (85 % effectiveness). Deltamethrin was the compound that was reduced the fastest in each process. By contrast, difenoconazole concentrations were the most difficult to reduce. Using statistical analysis, the relationship between the properties of pesticides and the reduction of their concentration in cereals was clarified and showed a strong correlation.