Follow-up of the fate of imazalil from post-harvest lemon surface treatment to a baking experiment

<div><p>Imazalil is one of the most widespread fungicides used for the post-harvest treatment of citrus species. The separate use of peel during food preparation and processing may hitherto concentrate most of the imazalil into food products, where specific maximum residue limits hardly exist for this fungicide. In order to monitor comprehensively the path of imazalil, our study covered the monitoring of the efficiency of several washing treatments, the comparison of operative and related sample preparation methods for the lemon samples, the validation of a sample preparation technique for a fatty cake matrix, the preparation of a model cake sample made separately either with imazalil containing lemon peel or with imazalil spiking, the monitoring of imazalil degradation into α-(2,4-dichlorophenyl)-1H-imidazole-1-ethanol because of the baking process, and finally the mass balance of imazalil throughout the washing experiments and the baking process. Quantification of imazalil was carried out with an LC-ESI-MS/MS set-up, while LC-QTOF was used for the monitoring of imazalil degradation. Concerning the washing, none of the addressed five washing protocols could remove more than 30% of imazalil from the surface of the lemon samples. The study revealed a significant difference between the extraction efficiency of imazalil by the EN 15662:2008 and AOAC 2007.1 methods, with the advantage of the former. The use of the model cake sample helped to validate a modified version of the EN 15662:2008 method that included a freeze-out step to efficiently recover imazalil (>90%) from the fatty cake matrix. The degradation of imazalil during the baking process was significantly higher when this analyte was spiked into the cake matrix than in the case of preparing the cake with imazalil-containing lemon peel (52% vs. 22%). This observation calls the attention to the careful evaluation of pesticide stability data that are based on solution spiking experiments.</p>