Researches On Processing Factors For Pesticide Residues Of Citrus Products And By-products

Citrus is considered to be one of the major fruit crops produced in the world, citrus and its products, including citrus juice, pomaces feeds and essencial oils, are so large that brings about much economic values for the society. The quality and safety of citrus and its products are not only related to humans’health, but also related to the development of citrus industry. Pesticide residues are one of the main hazards of the citrus quality and safety, as well as one of the most important hazards of food. Good knowledge of the effects of food processing on pesticide residues can provide the basis for the optimization of processing technology. More importantly, it is necessary to properly assess human dietary exposure.In this experiment, firstly, the analysis methods of UPLC-MS/MS combined with the QuEChERS for determination imidacloprid, carbendazim, abamectin, cypermethrin, prochloraz, and GC-MS/MS combined with the QuEChERS for determination propargite were developed. The results indicated that the mean recoveries and Relative Standard Deviation (RSD) values (n=6) are ranging from 70.9%to 117%for imidacloprid, carbendazim, abamectin, cypermethrin, prochloraz with RSD lower than 21%. the recoveries of propargite were ranging from 70.4%to 102.3%with RSD (n=5) lower than 13%. The limits of detection (LODs) of all the pesticides were varied from 0.03 ug kg-1 to 3 ug kg-1. In a word, the testing methods were able to completely satisfy requirements of detecting pesticide residues.The Beibei 447 sweet oranges were selected as the RAC samples for this experiment. Field trials for imidacloprid. carbendazim, abamectin, cypermethrin and propargite were carried out to guarantee sufficient residue levels in RAC samples for further processing studies, The trees were sprayed with 5-fold the concentration of the maximum recommended dosage solutions, for a total of three sprayings with an interval of 7 days between sprayings. The fruits were picked 24 hours after the last spraying, and were sent immediately to the workshop for processing. The orange fruits were soaked with 5-fold the concentration of the maximum recommended dosage solutions of prochloraz, then drained and stored for three days before processing. All fruits sprayed with each pesticide were divided into three batches; each batch of samples was divided into three detection replicates. The main results were list as follows:(1) The pesticide residues were mainly distributed in orange peels, about 4.4%-17.9%of total relative pesticide residues were contained in the unwashed orange pulps. However, prochloraz was an exception, with 65.4%of the total residues present in the pulps of unwashed oranges. The residue levels of all the pesticides in peels were 1.16-4.44 times higher than pulps.(2) The residues distributed in the face of peels could be partially removed by washing during commercial processing of orange juice, the processing factor of juicing was ranged from 0.146 to 0.675; low residue levels were observed in squeezed juice, and the processing factor was ranged from 0.044 to 0.111, filtrating could further reduce all the pesticide residues. There was only 0.55-3.14%of the total relative pesticide residues were contained in NFC juice, the residue level of cypermethrin, and prochloraz in NFC juice were decreased comparing with the filtrated juice samples, but the residue level of abamectin was unchanged and the concentration of imidacloprid and carbendazim were increased. After concentration, the residue levels of cypermethrin and prochloraz were reduced, but the levels of imidacloprid, carbendazim and abamectin were increased. However, the residue levels in concentrated juice were also very low, and the processing factors of concentrated juice were ranged from 0.002 to 0.071. (3) Some pesticide residues had been translocated to pomace during juicing, and the processing factor of pomace was ranged from 0.007-1.282. The residue levels of imidacloprid and carbendazim in orange oil were reduced and the processing factor was 0.016 and 0.038. respectively, but the other 3 pesticides were concentrated in orange oil, and the concentrated factor of abamectin, prochloraz and cypermethrin was 28.160,5.232 and 5.621. respectively.The National Theoretical Maximum Daily Intake (NTMDI) and National Estimated Daily Intake (NEDI) were applied to assess the dietary exposure of pesticide residues in orange fruits and juice, the results were list as follows:(1) The risk index of all the pesticide residues in citrus fruits were less than 100%after assessment by NTMDI and NEDI, that is to say the risk is accepted. The exposure risk was reduced along with the age increasing due to the change of body weight and dietary habit. The dietary exposure of females is higher than males because of the gender discrepancy that caused by the difference of body growth and dietary habit.(2) Owing to the processing factor had not been considered, the results assessed by NTMDI is higher than NEDI, which is fully considered the effect of processing during assessment. What’s more, the risk index assessed by NEDI of the pulps of washed whole fruits is lower than unwashed whole fruits.(3) The risk of pesticide residues in orange juice is assessed by NEDI; the results indicated that the risk in orange juice is very low; the risk index of prochloraz was 0.144%, and the other 5 pesticides risks were lower than 0.0104%.