Comparative study of screening methodologies for ochratoxin A detection in winery by-products

The worldwide contamination of winery by-products by mycotoxins may present a serious hazard to human and animal health. Mycotoxins are secondary metabolites of fungi with possible adverse effects on humans, animals, and crops that result in illnesses and economic losses. Mycotoxins are under continuous survey in Europe, but the regulatory aspects still need to be set up for winery by-products, which may be used in animal feed. The aim of this study was to implement a simple but reliable analytical methodology for ochratoxin A (OTA) quantification in grape pomaces in order to perform a survey of samples from the Douro Demarcated Region, Portugal. The method involved a unique preparation step, solvent extraction, followed by high-performance liquid chromatography (HPLC) with fluorescence (FL) detection. A comparative study was performed with two extraction solvents (ethyl acetate and methanol) as well as using extraction on an immunoaffinity column. The linearity range for OTA analysis was 0.05-23.5 microg L(-1) with a detection limit of 0.05 microg L(-1) and a precision (expressed by the coefficient of variation under repeatability conditions) of 0.4-14.7%. The percentage of recovery was on average 23.5 +/- 3.6% (extraction with ethyl acetate) or 70.1 +/- 2.5% (extraction with 70% methanol). Accounting for the recovery factor and the chromatographic detection limit, as well as the preconcentration factor, the limit of detection in grape pomaces is 0.04 microg kg(-1) (ethyl acetate extraction) and 0.33 microg kg(-1) (methanol extraction). Samples from 12 out of 13 sites in the Douro Demarcated Region showed OTA presence with concentrations not exceeding 0.4 microg kg(-1). Both developed methods for evaluation of OTA in grape pomace are simple but efficient.