Residue changes of five pesticides during the production and storage of rice flour

Abstract

ABSTRACT The residue changes of five pesticides in samples from different steps of rice flour production and accelerated storage were systematically investigated. Rice flour was produced both by the extrusion process and the drying on roller process. The change of pesticide residues varied in different processing steps and storage time. The water adjusting step had little influence on the pesticide residues. The pesticide residues were decreased significantly in the extruding, soaking, and grinding steps with reduction from 21% to 76%. The drying step increased or decreased the pesticide residues in varying degrees through concentration due to water evaporation and thermal evaporation or thermal degradation. All the pesticide residues decreased during the accelerated storage, especially for methidathion and chlorpyrifos, neither was detected after accelerated stored for 14 days. The processing factors (PFs) for imidacloprid and isocarbophos in the drying step were greater than 1, and the others were all less than 1. The whole drying on roller process had lower PFs than the whole extrusion process, indicated that the drying on roller process had a greater effect on pesticide residues. The PFs of accelerated storage for five pesticides were all below 1. Overall, this study provides important references for monitoring pesticide residues in the processing and storage of rice flour. Moreover, the PFs obtained in this study could be useful in the dietary exposure and risk assessment of pesticides in rice flour.