Residual dynamics of pyraclostrobin in citrus juice processing

To assess the residual dynamic of pyraclostrobin during citrus juice processing, the field trials were conducted in Jiangjin District, Chongqing City and Hongjiang City, Hunan Province in 2019 with application of 40% pyraclostrobin + prochloraz water emulsion at five-fold maximum recommended dosage (166.7 mg a.i./kg) for three times on sweet orange, and citrus samples after application were processed according to the typical commercial processing procedure of orange juice, and the processed samples were finally determined by QuEChERS method combined with HPLC-MS/MS. The method validation results showed that, within the linear range of 0.0025-0.5 mg/L (except it was 0.005-1 mg/L for the matrix of peel essential oil), the matrix matched calibration curves of pyraclostrobin fit the linear relationship in both citrus processing products and cleaning liquid with correlation coefficient greater than 0.990 5. The average recoveries of pyraclostrobin in citrus processing products and cleaning liquid ranged from 63 % to 110 % and the relative standard deviation was 1.3%-9.6% at the three spiking levels of 0.01, 0.1 and 2 mg/kg (0.2, 2 and 20 mg/kg for peel essential oil). The results of citrus juice processing showed that the residues of pyraclostrobin in juice decreased significantly during the juicing process with the best estimated processing factor (PF) of <0.02, while pyraclostrobin was enriched in citrus peel essential oil and pomace with the best estimated PF of 15.6 and 1.2, respectively. This study provided reference for the dietary risk assessment of pyraclostrobin in orange juicing process.