Quantitation of ochratoxin A in South African wines

The natural occurrence of the carcinogenic mycotoxin ochratoxin A (OTA) in wines sold in local retail outlets in South Africa and Italy was investigated by HPLC analysis with fluorescence detection following cleanup by immunoaffinity column. All 24 local South African wines tested (15 white and 9 red) were found to contain detectable levels (> 0.01 μg/L) of OTA, with a mean of 0.16 μg/L in the white wines and a mean of 0.24 μg/L in the red wines. Results were subsequently confirmed by LC-MS analysis using positive ion electrospray ionization with collision-induced dissociation of the protonated molecular ion [M + H]+ at m/z 404 and selected reaction monitoring of the resultant product ions [M + H - H2O - CO]+ at m/z 358 and [M + H - H2O]+ at m/z 386. Comparison with the fluorescence method gave a significant correlation (r= 0.87; p < 0.01). Although OTA contamination was present in all of the South African samples analyzed, levels were well below the suggested European Union limit of 0.5 μg/kg. The highest level found in a locally purchased wine was 0.39 μg/L in a blend of local and imported Spanish red wine. Of the eight Italian wines analyzed, only two red wines were contaminated above the suggested maximum level.