Ochratoxin- and aflatoxin-producing fungi associated with green and roasted coffee samples consumed in Argentina

Abstract

The aims of this work were to identify the Aspergillus sections Nigri and Flavi , and to evaluate the natural occurrence of ochratoxin A (OTA) and aflatoxins in green and roasted coffee bean samples. The capacity to produce these toxins by Aspergillus species was also studied. Fifty samples of Colombian coffee beans (25 green and 25 roasted) were obtained from a processor plant located in the south of Córdoba province (Argentina). OTA and aflatoxin analysis were performed by high performance liquid chromatography (HPLC). OTA production by strains belonging to Aspergillus niger aggregate were cultivated using YES medium and detected by HPLC. Aflatoxin production was tested in strains belonging to section Flavi on malt extract agar and was detected by thin liquid chromatography (TLC). From green coffee samples, the predominant species isolated belonged to A. niger aggregate, 60 and 55%, in dichloran rose bengal chloramphenicol agar (DRBC) and dichloran 18% glycerol agar (DG18) respectively. While A. flavus strains were isolated in 14% from DRBC and A. parasiticus strains in 12% and 28% in DRBC and DG18, respectively. From roasted coffee samples, A. flavus was the most predominant fungi, isolated in similar percentages from both media (28%); followed by A. niger aggregate isolated in 28 and 14% in DRBC and DG18, respectively. In green and roasted coffee samples mean colony counts ranged from 2×10 3 to 3.5×10 4 colony forming units per gram of sample (cfu/g). OTA and aflatoxins were not detected in any sample analyses (<1 and 0.5 ng/g for OTA and aflatoxins, respectively). Twenty-five percent of black Aspergillus strains were OTA producers. The total of A. flavus strains assayed produced aflotoxin B 1 (AFB 1 ) and 80% of the A. parasiticus strains were AFB 1 and aflotoxin G 1 producers. The high percentage of A. flavus and A. parasiticus aflatoxin-producing strains suggest a potential risk for contamination in coffee with aflatoxins.