Pesticides are widely used in conventional agriculture to obtain a better yield for crops. They can cause toxic effects (headaches, cancer, reproductive harm and endocrine disruption). The main exposure to pesticides for humans is via food (especially by fruit and vegetables). Processing food can affect the level of pesticide residues and in some special case, more toxic by-products can be formed during processing. Different studies have been related to measure concentrations of pesticide residues after home or industrial processing. However, many processing factors (residues level in processed commodity/residue level in raw commodity) remain unknown and are necessary to estimate the level of pesticide exposure at the point of consumption after processing. To reach this objective, the combination carrots/pesticides (boscalid, chlorpyrifos, difenoconazole, dimethoate, linuron and tebuconazole) was chosen in collaboration with the Belgian Federal Agency for Safety of the Food Chain based on the number of non compliant samples, frequency and concentration level observed and on the toxicity of the pesticides. Treated carrots were grown in Belgium by Redebel sa. The amount of the pesticide residues observed in the raw material varied due to the different treatments, application times, weather conditions, the physico-chemical properties of each pesticide. Food processing (washing, peeling, blanching, microwave cooking, pasteurization and sterilization) was carried out on industrial pilot scale. Pesticides and the degradation products formed during processing were analyzed with GC–MS/MS and UHPLC–MS/MS. The washing step allowed decreasing the concentration of residues for all pesticides up to ~90%. The second process, peeling, results in a reduction comparable to washing. The blanching step, combining heat with a large quantity of water, enhanced the elimination of residues. Even residual concentrations were below 5 ppb, it was observed that microwave cooking did not reduce the level of residues while in-pack sterilization decreased most of the pesticide residues still present except difenoconazole. To conclude, most of the processing factors could be explained in terms of water solubility, the log-octanol-water-partitioning coefficients, the systemic properties of the pesticides studied and the agricultural practices.
