Background and purpose: Pesticide residues in food products is of great concern. Food preparation highly influences the pesticide residue and safety of the food. The aim of this study was to evaluate the effects of storage and different washing solutions on dichlorvos residue in tomato.

Materials and methods: A Interventional study was performed in which tomato samples were harvested after 24 h of dichlorvos spraying and their dichlorvos concentration was determined. A group of samples was stored in room or refrigerator temperature for 10 days. Dichlorvos changes were recorded every two days and the samples were washed for 20 s. The changes in dichlorvos residues were recorded again after washing the tomatoes. The second group of samples was immersed for 10, 20 and 30 min in water and solutions of 1, 2 and 3% sodium chloride, acetic acid and sodium bicarbonate. The impact of each treatment on residue was evaluated by gas chromatography equipped electron capture detector.

Results: Dichlorvos residue reduced during storage and its concentration in samples stored at room and refrigerator temperature reached to lower than the maximum residual limit (MRL) after 8 and 10 days, respectively. Thirty min of immersion in water and solution of sodium chloride, acetic acid and sodium bicarbonate caused 35.75, 34.62, 14.48 and 92.74% reduction in levels of dichlorvos, respectively. Sodium bicarbonate solution, depending on its concentration and washing time, had the highest impact on dichlorvos removal and acetic acid solution was found to have the lowest effect.

Conclusion: In order to remove dichlorvos from tomato and increase its safety, it is necessary to consider the preharvest interval (PHI) and its immersion in alkaline solutions for suitable time.