Determination of ochratoxin A in grapes of Greek origin by immunoaffinity and high-performance liquid chromatography

Abstract

A simple analytical method for ochratoxin A (OTA) determination in grapes is described, using aqueous methanolic extraction, an immunoaffinity column clean-up step and high-performance liquid chromatography with fluorescence detection. Mean recovery was 94% (RSD = 4.0%) with a detection limit of 0.4 ng g⁻¹ and quantification limit of 1.20 ng g⁻¹. Repeatability (r) and reproducibility (R) were 1.17 and 1.34, respectively. OTA determinations were applied to 50 grape samples (23 different varieties) originating from representative regions of Greece. Results showed the presence of OTA in 86% of samples tested (n = 50). Traces were found in 56% of samples but OTA was not detectable in 14% of samples. Traces were also found in 4% of red, organically grown samples. The most contaminated were three samples of red grapes, two from Central Greece (2.69 and 1.41 ng g⁻¹), both table and wine-making grapes. The third sample (1.46 ng g⁻¹), originating from the island of Samos, was used only in wine-making. Mean (1.06 ng g⁻¹) and median (0.76 ng g⁻¹) OTA concentrations in red grapes were slightly higher compared to the mean (0.82 ng g⁻¹) and median (0.65 ng g⁻¹) concentrations in white grape samples. The study shows that the potential risk for a person of 60 kg ranged from 0.9 to 9 ng kg⁻¹ bw day⁻¹ and is dependent on the quantity of grapes consumed daily.

Keywords:

• Ochratoxin A
• grapes
• immunoaffinity
• HPLC
• risk assessment

Acknowledgements

This work was supported in part by the University of Athens, Special Account for Research Grants (70/4/2508).