Mycoflora and occurrence of aflatoxin B1 in dried yam chips from markets in Ogun and Oyo States, Nigeria.

Seventy-six samples of dried yam chips locally called elubo isu were purchased in 2000 from markets in Ogun and Oyo States of southwestern Nigeria. The samples were assessed for pH, moisture content, associated fungi and aflatoxin B1 contamination. The pH of samples ranged from 5.6 to 6.1,while the moisture contents varied from 6.8 to 14.5% in Ogun samples, and 7.1 to 13.6% in samples from Oyo. Aspergillus and Penicillium were the two prevalent genera of fungi, and the number of colony forming units per gram of these two genera in the yam chips studied exceeded the tolerance limit in foodstuffs. The other fungal genera isolated included Botryodiplodia, Cladosporium, Fusarium, Rhizopus, Mucor, Aureobasidium and Paecilomyces. The two most frequent fungal species were A. niger and A. flavus. Thin layer chromatographic analysis showed that 17 samples or 22% contained aflatoxin B1 beyond the detection limit (5 ppb), but only three samples or 4% had toxin level above 30 ppb, the tolerance level in food for human consumption. The mean concentration of aflatoxin B1 in positive samples was 27.1 ppb.