Occurrence and thermal stability of the mycotoxin citrinin

桔霉素是一种由曲霉属、青霉属和单核菌属产生的真菌毒素，主要存在于谷物中，浓度较低，在加工谷物样品中浓度低得多。这种差异清楚地表明，食品加工对桔霉素水平有很大影响。此外，最近的人体生物监测数据显示，在大多数分析的欧洲尿液样本中，桔霉素在较低的ng/mL范围内均可检测到。人体生物监测数据以及原料和加工谷物中桔霉素水平之间的差异清楚地表明，根据食物摄入量计算的接触量与发生率数据之间存在差距。已表明桔霉素是一种反应性真菌毒素，在纯溶液或固体中加热时可转化为降解产物。然而，描述桔霉素在现实食品基质存在下的热反应以及桔霉素与基质组分的潜在结合的研究尚未进行，并且是本提案的主题。使用模拟食物成分如碳水化合物、还原糖和蛋白质的模型化合物，将研究桔霉素的降解和反应产物的形成。在第二步中，将在经典的热加工过程中，如烘焙和挤压蒸煮，研究桔霉素在复杂基质中的热降解。首先基于HPLC-HRMS鉴别降解产物，然后进行分离和基于NMR的结构解析。为了检测基质结合形式的桔霉素，将对从桔霉素还原率高的烘焙和挤压蒸煮中获得的样品进行酶促或化学水解，并分析基质结合形式的桔霉素单体。此外，将使用猪盲肠模型研究基质结合形式桔霉素在胃肠道中的释放（和代谢）。将在细胞培养实验中研究形成的降解产物的细胞毒性。最后，将对市售食物样本中的桔霉素、潜在的热降解产物以及基质结合形式的桔霉素进行定量，以估计与人类接触的相关性。

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.