Changes in eleven pesticide residues in jujube (Ziziphus jujuba Mill.) during drying processing

Processing can concentrate residues or convert residues to more toxic metabolites in food. The residual behavior of 11 pesticides in jujube fruits during four drying processes (freeze-, oven-, sun-, and microwave-drying) was assessed. Jujube samples with residues of dichlorvos, malathion, chlorpyrifos, triadimefon, hexaconazole, myclobutanil, kresoxim-methyl, tebuconazole, epoxiconazole, bifenthrin, and cyhalothrin were obtained from field trials. The degradation rates of pesticides during four drying processes were between 11.4 and 95.1%. Pearson analysis showed that the degradation of pesticide residues in jujube during sun-, oven-, microwave-drying processing was related to vapor pressure and solubility in water of the pesticides. Furthermore, the effects of four drying processes on the processing factors (PFs) were investigated. After freeze-drying, PFs of pesticides were >1, except for chlorpyrifos, suggesting that the dietary exposure risk of pesticides from jujube might be increased if freeze-dried samples were used. After microwave-drying, the PFs of all pesticides were <1, indicating microwave-drying process can significantly reduce 11 pesticide residues in dried jujube.