Pesticide processing factors during corn germ oil extraction
Publication in collaboration with Terres Inovia and FEDIOL, OCL, vol. 30, 2023
In the absence of regulations on pesticide levels in crude oils, this study aims to assess the transfer factors for extrapolating the concentration limits established for seeds to crude corn oils.
Corn grain was spiked with 4 organophosphate insecticides (chlorpyriphos, chlorpyriphos-methyl, fenitrothion, pyrimiphos-methyl), 2 pyrethroids (cypermethrin and deltamethrin) and a pyrethroid synergist, piperonyl butoxide (PB), targeting a dose of 1 mg/kg grain.
The grains were processed in a pilot starch mill to separate the germs (wet process), then these germs underwent an oil extraction process in a mini-pilot comprising a thermal conditioning stage, mechanical extraction followed by solvent extraction and a desolvation-toasting stage for the cake. Analyses were carried out by gas chromatography coupled to an MS/MS detector. Pesticide levels were measured on grain, doped grain, sprouts, crude oil and meal.
Surprisingly, organophosphates and pyrethroids differed significantly in their behavior in the grain-to-germ transition. In the case of the former, 48% to 81% of the pesticides applied were found in the sprouts, compared with only 9-11% for the latter and 31% for PB. Using acetonitrile washing on doped seeds, it was shown that pyrethroids remained bound to the hydrophobic cuticle of the seeds.
From germ to oil, on the other hand, the initial hypothesis of almost total transfer of pesticides into the fat fraction of the material was confirmed. Concentration ratios of germ to oil cake averaged 0.019, 0.065 and 0.109 for organophosphates, PB and pyrethroids respectively. In the same order, 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.