Investigating the fate of substances in complex processes like food processing poses a major challenge in analytical chemistry. To simulate complex chemical reactions during food processing, current regulatory procedures for plant protection products include a high temperature hydrolysis of active substances at maximum temperatures of 120 °C in water. In the present study the fate of three exemplary active substances for plant protection products was investigated during realistic food processing steps and the findings were compared to results of current hydrolysis procedures.
Major differences between simulative and realistic processing trials were observed in this study. When heating the fungicide prochloraz in rapeseed oil, chemical reactions between an active substance and food ingredients were demonstrated for the first time. The degradation process of prochloraz led to a spectrum of eleven degradation products and was shown to be dependent on temperature, heating duration and the used type of oil. In contradiction to simulative hydrolysis studies the insecticide deltamethrin was found to be stable at temperatures up to 250 °C applied during high-temperature heating of tomato products. Additionally, potatoes were treated with the sprouting inhibitor chlorpropham and were stored for up to six months. After boiling, frying and baking processes of potatoes chlorpropham residues in edible products were reduced by 73% to 83% depending on the process. In contrast to the assumption of the European Food Safety Authority, no formation of the critical 3-chloroaniline was observed during potato processing.
The comparison between realistic processing trials conducted in this study and simulative conditions questions the suitability of the current regulatory procedure. Furthermore, the first-time identification of processing-induced degradation products raises concerns towards risk assessment of pesticide residues in food. The implementation of fate studies during realistic food processing steps into regulatory guidelines for plant protection products will further increase food safety and consumer protection.