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Original Articles

Reliable indirect competitive ELISA used for a survey of ochratoxin A in green coffee from the North of Paraná State, Brazil

, , , , , , , & show all
Pages 902-909 | Received 16 Jan 2006, Accepted 18 Apr 2006, Published online: 11 Feb 2011
 

Abstract

The performance of an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) based on a monoclonal antibody (mAb) for ochratoxin A (OTA) detection was evaluated in a comparative study with high-performance liquid chromatography (HPLC) analysis using 68 freshly harvested coffee samples from the North of Paraná State, Brazil. The anti-OTA mAb showed high specificity and low cross-reactivity with OTA analogues (OTB and OTα), but cross-reacted with OTC. This ic-ELISA showed a detection limit of 3.75 ngg−1 sample, when compared to 0.80 ngg−1 by HPLC, with an ic-ELISA/HPLC correlation coefficient of 0.90. As regards OTA analysis of these coffee samples, natural contamination was detected in 10 samples (14.7%) by both methods, where the ic-ELISA values (range 3.9–7.3 ngg−1) were 1.1 to 1.6-fold higher than HPLC data (2.7–4.7 ngg−1). Five samples (7.4%) were OTA positive (range 0.84–1.30 ngg−1) only by HPLC assay, probably due to the higher detection limit reached by ic-ELISA. OTA was undetectable in 53 samples (77.9%) by both methods, while all positive samples (range 0.84–7.30 ngg−1) showed OTA levels lower than 8 ngg−1 (maximum limit recommended by the European Union). The matrix interference of green coffee was minimized by dilution of sample extracts before carrying out the ELISA assay. This mAb-based ic-ELISA can be effectively applied for OTA screening in coffee, because it is simple, sensitive and sample preparation is easy.

Acknowledgements

The authors thank the CNPq (Brazilian Government Organization for grant aid and fellowship to Brazilian researchers), CAPES Foundation – Brazil (Foundation for the Coordination of Higher Education and Graduate Training), JICA (Japan International Cooperation Agency) and the UGF-SETI (the Paraná State–Brazil Government Secretary for grant aid) for financial support.

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