Occurrence of fungi and mycotoxins in peanuts during storage

In this study, we investigated the occurrence of mycotoxigenic fungi and mycotoxins in stored peanuts. Two types of peanuts, with and without shell, were stored for 12 and 6 months, respectively and the kernels from each type of peanut were collected and analyzed bimonthly. The stored peanuts were mainly contaminated with Aspergillus, Penicillium, and Fusarium species along with at least 26 other genera. Fungal frequency increased exponentially to reach 79.1±20.3% at 12 months of storage for peanuts with shell, whereas it increased sharply to 100% at 2 months for peanuts without shell. A. pseudoglaucus, A. chevalieri, and P. citrinum were prevalent in peanuts with shell, whereas A. flavus, P. crustosum, and P. polonicum were the most dominant species in peanuts without shell. Mycotoxin analysis revealed that ochratoxin A was detected in only one sample without shell (37.31 μg/kg), while aflatoxins were not detected. Fungal isolates known for mycotoxin production were confirmed to be producing various levels of mycotoxins in potato dextrose agar medium. Among the tested isolates (n=129), 59 (45.7%) produced aflatoxins (0.82-1,213.60 μg/kg), ochratoxin A (39.35-237.20 μg/kg), patulin (1.21-803.76 mg/kg), or fumonisins (0.27-13.70 mg/kg). To our knowledge, this is the first report on mycotoxin production by A. westerdijkiae, A. niger, A. welwitschiae, A. tubingensis, and P. expansum isolates from Korean peanuts. Overall, these results demonstrate the potential risk of not only aflatoxin and ochratoxin A but also patulin and fumonisin contamination in stored peanuts.