FT-IR spectroscopy for rapid screening of ochratoxin A in wheat

Ochratoxin A (OTA) is a mycotoxin produced by several species of the genera Aspergillus and Penicillium, and can be frequently found in a variety of foods and beverages, including cereals, coffee, cocoa, spices, beer, wine, grape juice, and dried fruits. Effective monitoring of OTA should be undertaken and achieved through reliable and rapid analysis. Therefore, increased efforts have been made to develop analytical methods suitable for rapid OTA screening. In the present work the potential of using infrared spectroscopic for the screening of 229 wheat samples naturally contaminated with OTA in the range of < 0.15-54 µg/kg was investigated. Samples were analysed by both Fourier transform near- and mid-infrared spectroscopy (FT-NIR, FT-MIR). After a suitable pretreatment of the raw spectral data (baseline in combination with standard normal variate), Partial-Least Squares-Discriminant Analysis (PLS-DA) and Linear Discriminant Analysis (LDA) classification models were used to differentiate highly contaminated durum wheat samples from low contaminated ones and the performances of the resulting models were compared. Models were developed using a cut-off limit set at 2 µg/kg OTA that is lower than the EC maximum limit for OTA in unprocessed durum wheat (i.e. 5 µg/kg). The spectral ranges considered were between 7500-4000 cm-1 for FT-NIR and 4000-400 cm-1 for FT-MIR. For each spectral range, the classification results of the external validation (70 samples) were expressed in terms of average prediction abilities and false compliant rates. The average prediction were 94% for FT-NIR range and 96% for FT-MIR range, independently from the classification model used (i.e. PLS-DA or LDA) thus confirming the reliability of the two statistical approaches used. False compliant rates of 9% were obtained for both spectral ranges and both classification models. These findings indicates that FT-NIR, as well as FT-MIR analysis, might be a promising, inexpensive and easy-to-use screening tool to rapidly discriminate wheat samples for OTA content and verify the compliance with the EU regulatory level. This work has been supported by the Italian Ministry of Education, University and Research (P.O.N. 2007-2013), project S.I.Mi.S.A. "New Strategies for Improvement of Food Safety: Prevention, Control, Correction".