Ochratoxin A in sultanas from Turkey I: Survey of unprocessed sultanas from vineyards and packing-houses

A method for the determination of ochratoxin A ( OTA) in sultanas from Turkey using extraction with a sodium bicarbonate solution ( 2% NaHCO3) followed by immunoaffinity clean-up and liquid chromatography with fluorescence detection was used to assess the frequency of occurrence and level of OTA. In-house validation was carried out with spiked samples at levels of 0.15, 1.5, 5.0 and 10 mu g kg(-1) and average recoveries were 91, 93, 87 and 89%, respectively. The limits of detection and limit of quantification in Turkish sultanas were 0.026 and 0.09 mu g kg(-1), respectively. A survey for the presence of OTA was carried out on 264 unprocessed sultana samples during the production seasons between 1998 and 2000 collected annually from vineyards and from packing-houses. The analyses of unprocessed sultanas showed that 32.2% of the total number of samples contained no detectable OTA, whereas 9.8% of sultana samples had OTA concentrations above 10 mu g kg(-1), and the remaining 58% had levels within the range 0.026-10 mu g kg(-1). There were big differences in median concentrations between years. Considering the year of production, it appears that sultanas produced in 1998 and 2000 showed the lowest incidence of OTA contamination ( median < 0.02 mu g kg(-1)), whereas 2002 showed the highest incidence ( median 4.3 mu g kg(-1)1). The overall mean OTA concentration was calculated as 3.4 mu g kg(-1), and the overall median as 0.9 mu g kg(-1). Among the samples analysed, the highest detected level of OTA was 54 mu g kg(-1).