Abstract: Objective: To assess the safety of flusilazole and ningnanmycin in citrus and its processed products, field trials were conducted in Chongqing and Hunan and orange juice processing was performed following the commercial procedure. The residue dynamics, processing factors and dietary risk assessment of flusilazole and ningnanmycin during orange juice processing were investigated. Methods: The quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure and solid phase extraction (SPE) were employed to develop a quantitative analytical method for flusilazole and ningnanmycin in orange and its processed products using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), respectively. Results: The sensitivity and accuracy of the established method were good. In orange peel essential oil at 0.05, 0.5, 2 and 20 mg/kg, the average recoveries of flusilazole were 78.5%–108.4% with relative standard deviation (RSD) between 0.5% and 6.6% at spiked levels of 0.01, 0.1 and 0.2 mg/kg. In orange peel essential oil at 0.05, 0.5, 5 and 20 mg/kg, the average recoveries of ningnanmycin were 88.3%–105.6% with RSD between 0.3% and 8.7% at spiked levels of 0.05, 0.5 and 5 mg/kg. The squeezing process was a highly effective way to reduce the residues of flusilazole and ningnanmycin, which were reduced by 93.3% to 98.6% in mother juice, respectively. Both compounds were prone to enrichment in orange pomace. The residue level of ningnanmycin in the peel essential oil was reduced while that of flusilazole was enriched. Processing factors less than 1 were observed for the other processed products. The risks of acute and chronic dietary exposure to flusilazole and ningnanmycin among different age groups were both lower than 100%, which were at an acceptable level. Conclusion: This study could provide a reference for residue behavior and dietary exposure risk assessment of flusilazole and ningnanmycin in citrus and its products, thereby promoting the scientific application of the two pesticides for disease prevention in the citrus industry.

Key words: flusilazole; ningnanmycin; citrus juice processing; pesticide residue; processing factor