Effects of different postharvest soaking methods on the removal of pesticide residues in cowpea

【Objective】To study the effects of different postharvest soaking methods on the removal of pesticide residues in cowpea, which could provide theoretical basis for cowpea quality and safety risk management and dietary risk assessment. 【Method】Cowpeas sprayed with chlorpyrifos,isocarbopho,omethoate and carbosulfan were harvested on the 1^st, 3^rd, 5^th and 14^th d after spraying, and then soaked in room temperature water, ice water and 1% ice alkali water for 5,10 and 15 min respectively. Without soaking treatment was as control. The residues of chlorpyrifos,omethoate, carbosulfan and isocarbopho in cowpea were detected, and the removal effects of different postharvest soaking methods on pesticide residues in cowpea were analyzed.【Result】Soaking cowpea in water, ice water and 1% ice alkali water could reduce the residues of cchlorpyrifos,omethoate,isocarbopho and carbosulfan to a certain extent. The best elution effect was obtained on the 5^th d after carbofuran and isocarbopho were sprayed in 1% ice alkali water for 15 min, and the removal rates were 69.37% and 49.67% respectively. On the 5^th d after spraying chlorpyrifos, the picked cowpeas were soaked in 1% ice alkali water for 10 min, and the removal rate was 44.94%. On the 1^st d after spraying omethoate, the best elution effect was obtained by soaking in 1% ice alkali water for 5 min, and the removal rate was 53.83%. On the 5^th d after spraying, the maximum pesticide residue of carbosulfan in cowpea treated by 3 soaking methods met the national limit value standard （≤0.01 mg/kg）. 【Conclusion】Chlorpyrifos,omethoate and isocarbopho within 5 d of spraying, through room temperature water, ice water and 1% ice alkali water can not reach the national limit standard. The forbidden and restriction of higly toxic pesticides in cowpea is very necessary in China.