Occurrence of ochratoxin A-producing fungi in commercial corn kernels in Argentina.

Potentially ochratoxigenic Aspergillus and Penicillium species were identified and the natural occurrence of ochratoxin A (OTA) in corn kernels was evaluated. Likewise, the capacity to produce OTA by Aspergillus section Nigri and Circumdati was investigated. A total of 50 corn samples for human consumption was collected in the south of Córdoba Province. The surface-disinfected method for mycobiota determination was used. The OTA detection was performed by HPLC. OTA production was tested in strains belonging to section Nigri and Circumdati. Statistical analysis demonstrated that the specie A. flavus was isolated in higher frequency (p<0.01) from corn kernels in DRBC and DG18 media. The percentage of corn kernels contaminated by A. niger var. niger was similar in DRBC and DG18 media. The frequency of grains contaminated by A. flavus and A. niger var. awamori was higher than A. niger var. niger and A. japonicus var. japonicus (p<0.01) in DG18 media. The other potentially ochratoxigenic species, A. ochraceus, was isolated between 5% and 10% of the corn kernels in DG18 and DRBC media, respectively. The OTA producing species P. verrucosum was not isolated. All samples of corn were OTA negative (<1 ng g(-1)). Thirty strains (25%) of the black Aspergillus were OTA producers. From four strains of A. ochraceus isolated, only one produced OTA. Due to the storage variable conditions could not be adequate in this substrate, the presence of ochratoxigenic strains of section Nigri and OTA needs to be evaluated for a longer time to establish the toxicological risk for human beings. The contamination of stored corn kernels with A. flavus and Aspergillus section Nigri was significant.