Use of monoclonal antibodies, enzyme-linked immunosorbent assay and immunoaffinity column chromatography to determine ochratoxin A in porcine sera, coffee products and toxin-producing fungi.

Ochratoxin A, produced by a number of fungal species, has been found in many milieu, including porcine sera and coffee beans. It was therefore analysed by enzyme-linked immunosorbent assay (ELISA) in porcine sera, coffee products and fungal cultures, using monoclonal antibodies, a monoclonal antibody-linked immunoaffinity column (IAC) and high-performance liquid chromatography (HPLC). The chloroform extracts of acidified porcine sera were assayed directly by ELISA, with alkaline phosphatase and horseradish peroxidase as marker enzymes, at detection limits of 0.1 and 0.01 ng/ml, respectively. The presence of ochratoxin A in ELISA was confirmed by HPLC. The average contents in the five different lots tested were: 0.4 ng/ml in lot A (19 samples), 0.36 ng/ml in lot B (104 samples), 5.20 ng/ml in lot C (17 samples), 1.24 ng/ml in lot D (23 samples) and 0.22 ng/ml in lot E (24 samples). ELISA of methanol extracts of rice cultures showed the presence of more than 0.1 ng/g in 3 of 15 isolates of Aspergillus, in 16 of 67 isolates of Penicillum and in 7 of 17 isolates of Eupenicillum; none was found in an isolate of Emericella. IAC-HPLC analysis revealed that P. foetidus, which is similar to A. niger and is used for the production of a Japanese alcoholic drink (shou-chuu), also produced ochratoxin A. Use of IAC-HPLC to analyse coffee beans and instant coffee power resulted in the sharp resolution of ochratoxin A without complicated clean-up steps. The IAP-HPLC technique could thus be used for mass surveys of ochratoxin A residues in biological specimens.