Pesticide Residue Change In Drying Or Fermentation Process Of Jujube

Processing of agricultural products can affect the pesticide residue level seriously, making it decrease or increase. Hence processing study is essential to evaluate the safety of processed products based on the residue level in raw agricultural commodities (RAC). In processing studies, the processing factor (Pf) is a main parameter to evaluate the change of pesticide in RAC and related processed products. Pfis defined as the ratio of residue levels in processed commodities to those in RAC. It can be used to conduct refined dietary exposure assessments with RAC to assess consumer safety. In this research, effects of drying and fermentation process on the pesticide residues in jujube were evaluated.A multi-residue analytical method for determination of16pesticides in fresh and dried jujube samples was developed by using gas chromatography-mass spectrometry (GC-MS). The sample was extracted with acetonitrile or acetonitrile-water, cleaned up by dispersive solid phase extraction with the absorbent of MWCNTs. Fortified experiments were conducted at three levels. Recoveries were between76.7%and112.4%with relative standard deviations (RSDs) lower than12.3%. Limits of detection (LODs) and limits of quantification (LOQs) were0.001～0.01mg/kg and0.003～0.03mg/kg, respectively. The established method could meet the requirement for determination of residues in fresh and dried jujube samples.Effects of four drying methods including freeze-drying, oven-drying, sun-drying and microwave-drying on11pesticide residue levels in jujube were evaluated. Jujube samples with residues of dichlorvos, malathion, chlorpyrifos, triadimefon, hexaconazole, myclobutanil, kresoxim-methyl, tebuconazole, epoxiconazole, bifenthrin and cyhalothrin were from field trials. The results showed that (1) after freeze-drying process, Pfof malathion and chlorpyrifos was1.2and0.9, respectively, which indicated freeze-drying process had little influnce on the residues. The other pesticide residues increased with the Pfs from1.3to2.4.(2) after sun-drying process, Pfs of malathion, chlorpyrifos, triadimefon and tebuconazole residues were between0.8and1.2, which indicated the process had little influnce on the residues. The other residues increased (Pf:1.4-2.4), except dichlorvos residues (Pf=0.1).(3) after oven-drying process, Pf of dichlorvos was0.2, which indicated lower residue risk. Pfs of malathion and chlorpyrifos was1.1and0.8, which indicated the process had little influnce on the residues. The other residues increased (Pf:1.4-1.8).(4) after microwave-drying process, dichlorvos and chlorpyrifos residues decreased whose Pf was0.2and0.6, respectively. Pfs of malathion, triadimefon, hexaconazole, myclobutanil, kresoxim-methyl, tebuconazole, epoxiconazole, bifenthrin and cyhalothrin were between0.8-0.9, which indicated microwave-drying process had little influnce on the residues. Results showed the residues of triadimefon, hexaconazole, myclobutanil, kresoxim-methyl, tebuconazole, epoxiconazole, bifenthrin and cyhalothrin increased more during drying process relative to dichlorvos, malathion and chlorpyrifos. The change was found related to vapor pressure.Effects of fermentation process on the trasfer of pesticide residues in jujube were evaluated. The Pfs of dichlorvos, malathion, chlorpyrifos, triadimefon, hexaconazole, myclobutanil and bifenthrin in jujube wine and vingar were lower than0.8, which indicated pesticide residues in primary products could be used to evaluate those in processed samples. Pf of triadimenol, metabolity of triadimefon, in vinegar (1.1) was lower than that in wine (1.4) due to the different environment. So it is necessary to focus on the metabolite during processing.The results could provide data to establish MRL values for processed products and provide guidance on the improvement of processing technique to decrease pesticide residues.