Abstract

A total of 150 ready to use food thickeners were randomly collected from various markets in both urban and rural settings. Four of the samples tested Achi (Brachystegia eurycoma), Akpalata (Afzelia africana), Ofor (Detarium microcarpum), and Ukpo (Mucuna flagellipes) were contaminated with fungal flora. The most common and prevalent  fungi  observed on incubated powdered form of food thickeners on media, were the Aspergillus group namely Aspergillus flavus,Aspergillus parasiticus and Aspergillus niger. Pure isolates of A. flavus and A. parasiticus from various food thickeners from open markets in Nigeria were screened for their potential to produce aflatoxin B₁ (AFB₁) on agar media. Ultraviolet (UV) light, a standard procedure was used to differentiate the toxin from non-toxin form of Aspergillus species. Further, aflatoxin quantification was done using thin layer chromatography (TLC) followed by fluorometry. A. flavus was more prevalent than A. parasiticus in all samples. Toxin and non-toxin isolates were grouped as per bright greenish-yellow fluorescence (BGYF) presumptive test under UV light. The amounts of AFB₁ from A. flavus isolates ranged between  0.94 to  3.83 µg/g of agar and all positive A. parasiticus  ranged from 0.22 - 2.87 µg/g of agar. Analysis of food thickeners also revealed a high incidence and alarming levels of naturally produced aflatoxin. The levels of AFB₁ ranged between 4.0 and 95 µg/g in various food thickeners tested. That the presence of aflatoxin in food thickeners poses a potential health threat to consumers in this part of Nigeria and elsewhere is discussed.

Key words: Ready-to-use food thickeners, Aspergillus sp., aflatoxin B₁, thin layer chromatography, fluorometry.