Transformation behavior of trichlorfon in apple during the drying process.

The transformation products of pesticide residues during the drying process were investigated. Trichlorfon transformed into dichlorvos during three drying processes of apples: hot-air drying, microwave drying, and sun drying. The conversion kinetics of trichlorfon and dichlorvos were fitted by curve regression, which mainly conformed to first-order kinetic and quadratic models (R2 = 0.69–0.98). Based on Spearman's correlation analysis, the changes of trichlorfon were mainly related to their physical and chemical properties (aqueous hydrolysis DT50, octanol-water partition coefficient). Microwave drying promoted the transformation of trichlorfon into dichlorvos. Hot-air drying had the highest scavenging capacity against trichlorfon and dichlorvos (99.8% and 99.4%, respectively); its temperature was the main factor affecting the transformation of trichlorfon into dichlorvos. Temperature was higher in hot-air drying (60 °C) than in sun-drying (20–28 °C), which may significantly reduce the levels of the two pesticide residues. The Toxicity Estimation Software Tool toxicity assessment showed that toxicity was greater for dichlorvos than trichlorfon. Therefore, production of dichlorvos should be avoided during drying. Hot-air drying was the optimum choice for drying apples. [ABSTRACT FROM AUTHOR]