Reducing Pesticide Residues on Tomato Through Appropriate Post-Spray Harvesting Time and Postharvest Washing

Pesticide residues are a serious problem in Cambodia’s vegetable sector. This study determined the pesticide residue levels on local and imported tomatoes in Phnom Penh markets and the effects of harvesting time after pesticide spraying and postharvest washing methods. Locally produced tomatoes had lower pesticide residues than imported tomatoes in supermarkets and wet markets. All pesticide levels were lower than the Codex Maximum Residue Limits (MRLs) while carbofuran, chlorfenapyr and chlorpyrifos were higher than the European Union (EU) MRLs. Field-grown tomatoes had highest pesticide residues after 1 day from spraying, which decreased thereafter but the trend differed with location. In Kandal province, all pesticides were lower than the Codex and EU MRLs after 14 days from spraying, except acetamiprid, while in Battambang province, all pesticides were not detected after 14 days from spraying. Nethouse-grown tomatoes were negative of pesticide residues except chlorpyrifos in Kandal and acetamiprid in Battambang. Removing pesticides on tomatoes inoculated with dimethoate, profenofos, endosulfan, cyhalothrin, cypermethrin, fenvalerate and deltamethrin was more effective with running tap water than 2% salt. When the two was combined (2% salt, then rinsing with tap water), the efficacy remarkably increased, removing 68.60-99.99% of the pesticides. Applying this treatment on tomatoes produced in Kandal and Battambang resulted in 60% removal of cypermethrin, the only pesticide detected. From the results, there is potential for integrating appropriate timing of harvesting and washing with combined 2% salt and water rinsing in enhancing food safety of tomatoes.