Cassava (Manihot esculenta) is one of the most important root tubers in Africa and serves as a food security crop for millions of people on the continent. According to a report by the Ministry of Food and Agriculture, Ghana (MoFA 2013) cassava ranks first among root crops in Ghana, with over 14 million MT of the crop produced in the year 2012. Customarily, cassava is largely consumed locally and does not return considerable amounts of foreign exchange. About 50 % of the roots are consumed fresh at household level, whilst the remainder is processed into other forms such as cassava chips and flour. Only 1 % of the cassava produced is used for industrial purposes.
In recent times attempts have been made to add more value to cassava and also make it more useful as a raw material for industrial applications. One of the approaches has been to process the roots into unfermented flour for domestic and industrial uses. This flour, also known as High Quality Cassava Flour (HQCF) is useful for bakery products, production of glucose syrup and starch as well as use as a glue extender for the plywood industry. HQCF can also serve as a source of starch for the textile industry.
Heavy metal and aflatoxin contaminants in foods have become a matter of public health concern in recent times (Aradhna et al., 2009). Heavy metals such as copper (Cu), iron (Fe), and zinc (Zn) are considered as essential elements because of their role as co-factors in metabolic and biosynthetic processes. Lead (Pb), arsenic (As), and mercury (Hg) are non-essential, for they have no known beneficiary roles and are toxic above certain levels. The essential metals may produce toxic effect at high concentrations (Celik & Oehlenschlager, 2007; Tuzen, 2009). Heavy metals accumulate in human organs such as liver, kidney, bone and causes severe health disorders. For example Pb can cause renal masses, affect cognitive development and may lead to adult cardiovascular disease (Bandara et al., 2008). Mercury is considered by WHO as one of the top ten chemicals or groups of chemicals of major public health concern. Mercury may have toxic effects on the nervous, digestive and immune systems, and on lungs, kidneys, skins and eyes (WHO, 2003). For fetuses, infants and children, the primary health effect of Hg is impaired neurological development. Arsenic is also considered as toxic. Ingestion of As leads to gastrointestinal symptoms, and disturbances of cardiovascular and nervous systems functions. Long-term exposure to As is casually related to increased risk of cancer (Xiong et al., 2013). Aflatoxins are known to be carcinogenic. Aflatoxin contamination in food is caused by the presence of Aspergillus flavus, Aspergillus nomius and Aspergillus parasiticus (Essono et al., 2009). These organisms usually contaminate the food product and synthesize the toxins as metabolites in the presence of high levels of carbohydrates and low levels of protein (Essono et al., 2009).
In the present study, variations in trace metal and aflatoxin content of cassava during processing into HQCF was assessed by determining the levels of As, Cu, Fe, Hg, Pb, Zn, aflatoxins B1, B2, G1 and G2 in raw cassava, grated cassava dough, dried grits, dried cassava chips, and HQCF. The levels of the contaminants were compared to WHO a specifications to ascertain the risk posed to the health of the general public.