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

Abstract

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 µg 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 µg 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 µg kg⁻¹, and the remaining 58% had levels within the range 0.026–10 µg 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 µg kg⁻¹), whereas 2002 showed the highest incidence (median = 4.3 µg kg⁻¹). The overall mean OTA concentration was calculated as 3.4 µg kg⁻¹, and the overall median as 0.9 µg kg⁻¹. Among the samples analysed, the highest detected level of OTA was 54 µg kg⁻¹.

Keywords:

• Ochratoxin A
• high-performance liquid chromatography (HPLC)
• dried vine fruits
• unprocessed sultanas
• mycotoxin

Acknowledgements

The authors express thank the Aegean Exporters’ Union/Dried Fruit Board (Izmir, Turkey) for support during the research work.