Study on the effect of grain storage and processing on deltamethrin residues in post-harvest treated wheat with regard to baby-food safety requirements

The effects of storage intervals and of milling procedures on dissipation of deltamethrin residues in post-harvest treated wheat grain were studied with the aim to obtain scientific data on compliance of the processed products with the safety requirements concerning baby foods. The insecticide formulation was applied on stored wheat at a recommended rate of active ingredient of 0.5 mg kg(-1) and at a higher rate of 4 mg kg(-1), performing the highest protective effect. The dissipation of residues and their distribution in different fractions of the milled grain were studied after various storage intervals, from 7 to 270 days after treatment. Eight fractions-bran, semolina, three types of groats, and three types of flour-were collected after milling of grain and analysed for determination of pesticide residues. The residues were determined by gas chromatography characterized by the limit of determination of 0.005 mg kg(-1), low enough for enforcement of the maximum residue level of 0.01 mg kg(-1) established by the European Commission Directive for any pesticide in cereal-based foods. Deltamethrin applied post-harvest on wheat as grain protectant was distinguished by low rate of degradation on the grain under practical storage conditions. One hundred and eighty days after treatment at an application rate of 0.5 mg kg(-1), the residues were between 0.03 and 0.2 mg kg(-1) in the various types of flour. Two hundred and seventy days after treatment at a rate of 4 mg kg(-1), the residues in the flour were in the range of 0.4-1.5 mg kg(-1).