Fungi and mycotoxins during conventional and improved postharvest processing and storage of local rice in Nigeria.

This study applied a polyphasic characterization approach and LC-MS/MS analysis to elucidate fungal and mycotoxin contamination dynamics during conventional (CPRP) and improved (IPRP) postharvest processing and a 90-day storage of rice in Nigeria. Three hundred and twenty-five fungal isolates belonging to 21 genera (10 moulds, one crust fungus, 10 yeasts) and 54 species were recovered from rice across both processing chains. The CPRP chain had greater diversity of fungal genera compared to the IPRP chain. Aspergillus predominated both processing chains while yeasts occurred only in the CPRP chain. Species belonging to Aspergillus sections Aspergillus, Candidi, Flavi and Nidulantes, and Penicillium section Citrina predominated in stored rice in the two processing chains. A total of 106 extrolites including several uncommon extrolites and potential species markers were identified in agar cultures of 38 strains from 19 mould species. Fifteen mycotoxins were detected in rice along the processing and storage chains. Processing of rice in the IPRP chain and hermetic storage for 90 days reduced total aflatoxins by 9% compared to non-reduction in CPRP chain. Conventionally processed and stored rice in jute bags after 90 days recorded at least twice higher percentage reductions of total fumonisin, nivalenol and tenuazonic acid compared to hermetically stored rice from the IPRP chain. However, citrinin+dihydrocitrinone levels in rice from the two storage types increased progressively during the 90-day storage period. This study highlights the critical control points in the two rice process chains and provides insights into possible mycotoxin control approaches along the chain including in storage.