Processing Induced Degradation Routes of Prochloraz in Rapeseed Oil

Analyzing the fate of substances in complex matrices, such as processed food, is a major challenge in modern analytical chemistry. However, current regulatory procedures for pesticides only include high temperature hydrolysis of the active substance in water (OECD 507) to simulate food processing. This study shows that heating radiolabeled [imidazolyl-2-¹⁴C]prochloraz in virgin rapeseed oil at temperatures up to 240 °C leads to an extensive degradation of the active substance. In total, 11 degradation products were identified. Several of these products were formed by reactions of the active substance with ingredients from the oil. 2-[(1-H-Imidazole-1-carbonyl)(propyl)amino]ethyl oleate (icpame-oleate), a reaction product of an oleic acid moiety and the prochloraz backbone, was identified for the first time. The quantification of prochloraz, icpame-oleate, imidazole, and 2,4,6-trichlorophenol demonstrated the dependency of the degradation process on temperature, heating duration, and type of oil. The obtained results in this study show the enormous impact of high temperature food processing on the fate of pesticides. The necessity to consider matrix related reactions in pesticide regulation is emphasized, and the suitability of the OECD 507 guideline is questioned. Concerning possible toxicological risks of novel degradation products, future studies will have to assess potential hazards or opportunities of food processing, ultimately yielding in safer food.