Lippolis Vincenzo, Pascale Michelangelo, Valenzano Stefania, Visconti Angelo
National Research Council of Italy (CNR), Institute of Sciences of Food Production (ISPA), Via G. Amendola 122/O, 70126 Bari, Italy.
J AOAC Int. 2012 Mar-Apr;95(2):452-8. doi: 10.5740/jaoacint.11-047.
The significance of laboratory sample preparation for the determination of two important mycotoxins, ochratoxin A (OTA) and deoxynivalenol (DON), in wheat was investigated by comparing water-slurry mixing and dry-milling procedures. The distribution of OTA and DON in 10 kg samples of naturally contaminated wheat was established by analyzing one hundred 100 g subsamples of each sample. A normal distribution and a good repeatability of DON measurements was observed for both water-slurry mixing (mean 2290 microg/kg, CV 4.6%, median 2290 microg/kg) and dry milling (mean 2310 microg/kg, CV 6.4%, median 2290 microg/kg) procedures. For OTA determinations, reliable results could be obtained only by slurry mixing sample preparation (mean 2.62 microg/kg, CV 4.0%, median 2.62 microg/kg), whereas dry-milling comminution resulted in an inhomogeneous distribution with a high variability (mean 0.83 microg/kg, CV 75.2%, median 0.60 microg/kg) and a positive skewness (2.12). Ad hoc experiments were performed on different size portions of the same sample (10 kg) to assess accuracy and precision of the comminution/homogenization procedures (slurry mixing and dry milling). Very good results were obtained for DON determination with both procedures in terms of accuracy (>98.7% of the "weighted value") and precision (CV <3%). For OTA determination good results were only obtained by slurry mixing (99.4% of the "weighted value," CV 10%), whereas dry milling provided results with low accuracy (43.2% of the "weighted value") and high variability (CV 110%). This study clearly demonstrated that sample preparation by slurry mixing is strictly necessary to obtain reliable laboratory samples for OTA determination in wheat to minimize misclassification of acceptable/rejectable lots, mainly within official control.
通过比较水浆混合和干磨程序，研究了实验室样品制备对测定小麦中两种重要霉菌毒素——赭曲霉毒素A（OTA）和脱氧雪腐镰刀菌烯醇（DON）的意义。通过分析每个10千克天然污染小麦样品的100个100克子样品，确定了OTA和DON在这些样品中的分布情况。对于DON测量，水浆混合（平均值2290微克/千克，变异系数4.6%，中位数2290微克/千克）和干磨（平均值2310微克/千克，变异系数6.4%，中位数2290微克/千克）程序均观察到正态分布和良好的重复性。对于OTA测定，只有通过水浆混合样品制备才能获得可靠结果（平均值2.62微克/千克，变异系数4.0%，中位数2.62微克/千克），而干磨粉碎导致分布不均匀、变异性高（平均值0.83微克/千克，变异系数75.2%，中位数0.60微克/千克）且呈正偏态（2.12）。对同一样品（10千克）的不同大小部分进行了专门实验，以评估粉碎/均质化程序（水浆混合和干磨）的准确性和精密度。对于DON测定，两种程序在准确性（>“加权值”的98.7%）和精密度（变异系数<3%）方面均获得了非常好的结果。对于OTA测定，只有通过水浆混合才能获得良好结果（“加权值”的99.4%，变异系数10%），而干磨提供的结果准确性低（“加权值”的43.2%）且变异性高（变异系数110%）。这项研究清楚地表明，对于小麦中OTA测定，通过水浆混合进行样品制备对于获得可靠的实验室样品至关重要，以尽量减少在官方控制中可接受/不可接受批次的误分类。
