Effects of oven drying on pesticide residues in field-grown chili peppers

The effects of drying on nine pesticides (chlorfenapyr, clothianidin, diethofencarb, folpet, imidacloprid, indoxacarb, methomyl, methoxyfenozide, and tetraconazole) in chili peppers were studied. The mean concentration factor calculated from weight reduction after drying by water loss was 5.28 for field 1 and 5.41 for field 2 (n = 10). Processing factors for pesticide residues in/on chili peppers after drying were 2.45–5.14 for field 1 and 1.71–4.53 for field 2, indicating that pesticide residues remaining in/on chili peppers were concentrated by usual drying process for pepper powder. The reduction factors reflecting net loss of pesticide residues during drying were 0.50–0.98 for field 1 and 0.44–0.98 for field 2. Drying caused a large reduction (37–49 %) in clothianidin, diethofencarb, imidacloprid, and tetraconazole; moderate reductions (16 and 22 %) in methomyl and methoxyfenozide; while did not affect the levels of chlorfenapyr, folpet, and indoxacarb (using conservative higher reduction factors from the two field trials).