Experimental determination of pesticide processing factor during extraction of maize germ oil

As there is a lack of regulations on pesticide levels in crude oils, this study aimed to evaluate transfer factors for extrapolating concentration limits established for maize kernels to the crude oils extracted from their germs. Maize kernels were spiked with 4 organophosphates insecticides (chlorpyriphos, chlorpyriphos-methyl, fenitrothion, pirimiphos-methyl), 2 pyrethroids (cypermethrin and deltamethrin) and a pyrethroid synergist, piperonyl butoxide (PB) targeting a dose of 1 mg/kg grain. The kernels were transformed in a pilot starch-mill to separate the germs (wet-milling) then these germs underwent an oil extraction process in a mini-pilot comprising a thermal conditioning stage, a mechanical extraction followed by a solvent extraction and a desolventization-toasting stage for the meal. Analyses were carried out by gas chromatography coupled to MS/MS detector. The pesticides content was measured on kernels, spiked kernels, germ, crude oil and meal. Surprisingly, a significant difference in behavior was observed between organophosphates and pyrethroids in the transition from grain to germ. For the former, the applied pesticides were recovered at levels between 48% and 81% in the germ, compared to only 9–11% for the latter and 31% for PB. It has been shown by means of acetonitrile washing on spiked seeds that the pyrethroids remained bound to the hydrophobic cuticle of the grains. On the other hand, from the germ to the oil, the initial hypothesis of an almost total transfer of the pesticides in the fat fraction of the material was confirmed. The germ to meal concentration ratios were on average 0.019, 0.065 and 0.109 for organophosphates, PB and pyrethroids respectively. In the same order, the concentration ratios between germ and crude oil were 1.87, 1.98 and 2.17. Grain to final oil transfer factors ranged from 7.4 to 12.7 for organophosphates, 4.8 for PB and 1.4 and 1.7 for cypermethrin and deltamethrin respectively.