Occurrence and thermal stability of the mycotoxin citrinin

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Citrinin is a mycotoxin produced by Aspergillus, Penicillium and Monascus species found predominantly in the lower µg/kg range in cereals and in much lower concentrations in processed cereal samples. This difference clearly demonstrates that food processing has a strong impact on citrinin levels. Furthermore, recent human biomonitoring data show that citrinin is detectable in the majority of the analyzed European urine samples in the lower ng/mL range. The human biomonitoring data and the discrepancy between citrinin levels in raw material and processed cereals clearly demonstrate that there is a gap between exposure calculated from food intake and occurrence data. It has been shown that citrinin is a reactive mycotoxin which can be converted to degradation products when heated in pure solutions or as solid. However, studies describing thermal reactions of citrinin in the presence of realistic food matrices as well as the potential binding of citrinin to matrix-components have not been performed yet and are the subject of this proposal. Using model compounds mimicking food constituents such as carbohydrates, reducing sugars and proteins the formation of degradation and reaction products of citrinin will be investigated. In a second step, the thermal degradation of citrinin in complex matrices will be studied during classical thermal processing such as baking and extrusion cooking. The identification of degradation products will be first performed based on HPLC-HRMS followed by isolation and NMR-based structure elucidation. For the detection of matrix-bound forms of citrinin, samples obtained from baking and extrusion cooking with high reduction rates of citrinin will be enzymatically or chemically hydrolyzed and analyzed for monomers of matrix-bound forms of citrinin. Furthermore, the release (and metabolism) of matrix-bound forms of citrinin in the gastrointestinal tract will be studied using the pig cecum model. The cytotoxicity of formed degradation products will be investigated in cell culture experiments. Finally, citrinin, potential thermal degradation products as well as matrix-bound forms of citrinin will be quantified in commercially available food samples in order to estimate the relevance for human exposure.