Mycobiota and aflatoxins associated with imported rice grains stored in Uganda.

Abstract

Milled rice grains imported into Uganda from Pakistan were investigated for natural contamination by fungi and aflatoxins. The direct plating method using five isolation media was used to enumerate and isolate the fungi during a 270-day storage period. Fungi were isolated and identified to species level and the percentage contamination levels were calculated. A total of 35 species belonging to 16 genera were recorded. The broadest species spectrum were found in the genera Aspergillus, Penicillium, Eurotium and Fusarium, which were represented by 11, 7, 4, and 3 species, respectively. Throughout the storage period, xerophilic fungi including Aspergillus candidus, Eurotium amstelodami and E. chevalieri were predominantly isolated. Species of the genus Penicillium (particularly P. pinophilum) and its teleomorph Talaromyces ranked second in predominance, while Aspergillus flavus, Fusarium spp. and other field fungi occurred only sporadically. Aflatoxins were recorded in rice samples during most storage periods with one sample recording 20–50 ppb. The moisture content increased in rice grains attaining values of over 14 % from the 180 day of storage onwards. A positive correlation was observed between moisture content and incidence of xerophiles, including A. candidus and E. amstelodami.