Occurrence of aflatoxin- and ochratoxin A-producing Aspergillus species in Thai dried chilli

Abstract

The present study aimed to examine the presence of aflatoxin- and ochratoxin A (OTA)-producing fungi in dried chilli ( Capsicum spp.). A total of 120 chilli samples, including 60 samples each of chilli powder and dried chilli pods, were examined for fungal contamination. Results showed that 86.7% and 96.7% of chilli powder and dried chilli pods, respectively, were contaminated by fungi at a concentration of <10 3 CFU/g. Overall, 500 fungal isolates were recovered and identified using a morphological method. The most frequent strain was Aspergillus section Flavi (46.6%), followed by Aspergillus section Nigri (34%), Penicillium (7.6%), Aspergillus section Aspergillus (7.6%), Aspergillus section Circumdati (2.2%) and Rhizopus (2%). In total, 37.5% and 43.8% of Aspergillus section Flavi isolates obtained from dried chilli powder and dried chilli pods, respectively, produced aflatoxin. Of the 96 aflatoxigenic isolates, 96.9% of the strains produced aflatoxin B and 3.1% produced both aflatoxin B and G. However, β-tubulin sequence analysis revealed that all aflatoxin-producing isolates were identical to A. flavus . Moreover, 170 isolates of Aspergillus section Nigri , 11 of Aspergillus section Circumdati , 2 of Aspergillus section Flavi producing yellow-to-cinnamon colonies and 38 of Penicillium spp. were examined for their ability to produce OTA. In total, 1 isolate of Aspergillus section Nigri and 2 isolates of Aspergillus section Flavi produced OTA. The first isolate was identified as A. carbonarius , whereas the latter two isolates were both A. alliaceus . The highest OTA production by A. carbonarius (622.4 ng/g) was observed following incubation on MEA at 25 °C for 21 days. Conversely, the two A. alliaceus isolates produced OTA at levels of 583.7 and 743.7 ng/g, respectively, after cultivation on YES at 25 °C for 21 days. To the best of our knowledge, this is the first report regarding the natural occurrence of aflatoxin- and OTA-producing fungi in dried chilli from Thailand. • More than 95% of dried chilli powder and dried chilli pods collected in Thailand was contaminated with fungi. • Aspergillus section Flavi is the most common species in dried chilli. • Aspergillus section Flavi in dried chili samples is frequently aflatoxigenic strain. • Ochratoxin A producing species, A. carbonarius and A. alliaceus , were detected in dried chilli powder.