Degradation of Five Organophosphate Pesticides in French Bean during Cooking Processes

The effects of cooking on the residue levels of monocrotophs,chlorpyrifos,malathion,parathion and dichlorvos in samples of French bean were determined by gas chromatography.The results showed that the residues of pesticides were decreased except monocrotophs during frying.The degradation rate ranged from 37.6 % to 85.1%.The frying time was more impacting to dichlorvos degradation than those of other pesticides.The degradation rate of dichlorvos was 37.6% after 5 min frying,and 65.2% after 7 min frying,while no significant changes of degradation rate were observed on other four pesticides.Losses of the residues due to processing were as following: stir-frying,7.6%~56.5%;steaming,23.0%~63.4%;boiling in a uncovered utensil,39.5%~81.7%;boiling in a covered utensil,42.0%~86.4%.When boiling the French bean for 10 min in a covered utensil,the residues in the soup was ranged from 0.03 to 0.50 mg/L.After 2 min heating by microwave,the degradation rates of five pesticides in French bean which have been stir-fried were 21.0%~41.5%.