Occurrence of aflatoxins in rice and in cassava (Manihot esculenta) products (meal, bread) produced in Guyana
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A survey was conducted on Guyana’s main staple foods, rice, cassava meal and cassava bread to determine the presence and concentration of aflatoxins (AFs) using enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC) with fluorescence detection for concurrence. Aflatoxins are secondary metabolites of the fungus Aspergillus and can be a health risk to humans and animals. Results were compared with European Union Commission (EUC) maximum levels of total aflatoxins of 10 μg/kg. Various types of rice (paddy, steamed paddy, cargo rice, white rice and parboiled rice) were randomly collected either directly from the field and rice mills in Guyana during the November 2015/March 2016 season. Of the total 186 composite samples of rice fractions collected from field and mills, 10% (19) had AF concentrations greater than the maximum EUC level of 10 μg/kg. Fifteen samples had aflatoxin concentrations ranging from 10 to 171 μg/kg, mean 54.4 μg/kg; four samples were outliers. Since Guyanese consume mainly white and parboiled rice, composite samples were taken along the marketing chain at points of sale to determine the presence of AFs. Of the sixty samples of white rice collected, 6.7% (4) had AF concentrations greater than the EUC regulatory limits ranging from 31.9 to 131 μg/kg, mean 80.8 μg/kg. For the 57 samples of parboiled rice, 3.5% (2) samples exceeded the limit with values of 72.6 and 407 μg/kg. Forty (40) samples each of cassava meal and cassava bread were analysed fresh and after 2 months of storage, and no sample exceeded the ELISA detection limit of 0.5 μg/kg.
KeywordsRice fractions Cassava meal Cassava bread High-performance liquid chromatography (HPLC) Enzyme-linked immunosorbent assay (ELISA)
We are grateful to the Department of Animal Sciences, University of Missouri-Columbia for its financial and technical support, Dr. Elroy Charles of the University of Guyana for advice on the statistical analysis and undergraduate student Ms. Joylene Hamilton for assistance with collecting and analysing the cassava meal and cassava bread samples.
This work was supported the University of Guyana Science and Technology Support Project (UGSTSP) funded by the World Bank.
Compliance with ethical standards
Conflict of interest
The authors declare that there is no conflict of interest.
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