Preservation of citrus fruit, and dissipation by diffusion and degradation of postharvest pesticides during storage

We investigated the effects of residues of the postharvest pesticides 2,4-dichlorophenol, carbendazim, iprodione and prochloraz in citrus fruits, where they were encountered in average contents of 0.765 & PLUSMN; 0.060, 0.367 & PLUSMN; 0.030, 0.739 & PLUSMN; 0.055, and 0.929 & PLUSMN; 0.074 mg kg-1, respectively, and exhibited half-lives of 6.47-77.00 d upon storage at 3 degrees C for 45 d. The contents in 2,4-dichlorophenol and carbendazim did not exceed the maximum residue levels (MRLs) set by the European Union (1.0 mg kg- 1) and China (5.0 mg kg-1). Preservatives added to Valencia citrus fruit (Citrus sinensis L. Osbeck) were degraded slowly at 3 degrees C. More than 50 % of their amounts remained on the fruit peel and never reached the pulp -by exception, the content in carbendazim of the pulp of oranges stored at 21 degrees C for 7 d was as high as 0.52 mg kg- 1, which testifies to the need for storage at lower temperatures. Residue degradation exhibited strong, negative correlation with temperature, the relationship between the degradation rate constant (k) and temperature being of the Arrhenius type. Carbendazim proved an effective preservative for citrus fruit. Fruits should be carefully controlled for residual pesticide levels in order to ensure that they are safe for human consumption.