THE EFFECT OF HOME PROCESSING ON POSTHARVEST FUNGICIDE RESIDUES IN CITRUS-FRUIT - RESIDUES OF IMAZALIL, 2-PHENYLPHENOL AND THIABENDAZOLE INHOME-MADE MARMALADE, PREPARED FROM LATE VALENCIA ORANGES

The effects of domestic marmalade-making procedures on residues of ima zalil, 2-phenylphenol and thiabendazole in 'sweet' oranges were invest igated by comparing residue levels in raw fruit and in marmalades, pre pared by heating the oranges with water and sugar for about 4 h in a p reserving pan on a gas ring or for about 1 h in a microwave oven. Dete rmination of residues in raw oranges and in mamlalades was carried out by extraction with dichloromethane, followed by clean-up and reversed phase HPLC with UV detection for imazalil and fluorescence detection for 2-phenylphenol and thiabendazole. Residue analysis showed that the extent of carry-through of imazalil, 2-phenylphenol and thiabendazole residues into the marmalades depended on the method of marmalade-maki ng and the nature of the fungicide. Persistence of fungicides was high er in the marmalade prepared in the microwave oven than in that prepar ed in the preserving pan. An increase (about 50%) in levels of imazali l in the fruit portions of marmalades compared with raw fruit residue levels indicated that imazalil was more readily extracted from oranges after processing. Comparison of 2-phenylphenol levels in raw fruit an d fruit portions of marmalades showed that the longer exposure to heat , needed for marmalade-making in a preserving pan, reduced residue lev els more severely (48%) than cooking in the microwave oven (13%). Thia bendazole levels in the fruit portion of marmalade prepared in the mic rowave oven stayed the same as in the raw fruit, but cooking in the