Abstract
Nine pyrethroid pesticides and 3 organophosphorus pesticides, which could not be removed during the oil refining process, were added to refined soybean oils at concentrations of 4 ppm each, and the oils were hydrogenated under 8 different conditions, then the persistence of these pesticides was examined. As a result, it was found that pyrethrin and permethrin persisted beyond other pesticides during hydrogenation and that these 2 pesticides decreased readily at a higher temperature, at a higher hydrogen flow rate or at a higher stirring speed. It was also clarified that any pyrethrin and permethrin persisting in an oil before hydrogenation can be eliminated by performing hydrogenation until the iodine value of the soybean oil attains 70 or less. Subsequently, pyrethrin and permethrin were added to a hydrogenated soybean oil at concentrations of 3 ppm each, and the oil was deodorized under the condition commonly used in oil plants, then the behaviors of these pesticides were examined. As a result, it was observed that the pyrethrin concentration was lowered below 0.01 ppm after deodorizing for 120 minutes, while permethrin remained at 0.32 ppm in the oil.
