The effect of drying processes on pesticide residues in orange (Citrus sinensis)

Abstract

The effect of different drying conditions (based on hot air convective drying and vacuum drying with or without microwave pretreatment) on residual behavior of abamectin, buprofezin, imazalil, and thiophanate-methyl in orange slices was investigated. Processing factors ranged between 1.55 and 3.41, indicating concentration of the residue levels in dried orange slices due to the moisture losses. However, based on the normalized residue concentration with dry matter content of the slices, pesticide residue levels in fresh orange slices reduced by 40.8%-73.2% after drying processes. Hot air drying caused more reduction in residue levels compared to vacuum drying. It was observed that decrease in absolute pressure of vacuum drying from 30 kPa to 15 kPa, increase in drying temperature from 60 degrees C to 80 degrees C, and application of microwave pretreatment increased the degradation rate. Moreover, the Pearson analysis revealed that degradation rate in the residue levels during drying was negatively proportional to the octanol-water coefficient of pesticides. Therefore, the highest degradation rate was obtained for buprofezin and thiophanate-methyl during hot air drying (at 80 degrees C) with application of microwave pretreatment and the lowest degradation rate was obtained for abamectin during vacuum drying (at 60 degrees C and 30 kPa).