Abstract
Cassava, an important food crop in the tropical regions of the world, is known to carry varying levels of cyanogenic glucosides that are potential poison to humans. In Tanzania, cases of cyanide poisoning have been reported in many cassava producing areas. This study was launched to quantify cyanide in fresh tubers of so called “sweet” cassava varieties and to gauge peoples’ perception on cyanide poisoning in Kagera and Morogoro regions. The study employed a questionnaire survey and a cross-sectional research design to identify different cassava varieties and their cyanide content using alkaline titration method. Findings showed that cyanide content in all of the analyzed tubers were above the internationally accepted levels in human consumables. Some sweet varieties were found to be wrongly classified as sweet because their cyanide content was above acceptable limits. For the same variety tubers sampled from a lowland area had significantly higher (P < 0.01) cyanide content than those from a highland point. It was also found that the upper (slippery) parenchymal tissue had more cyanide content (P < 0.05) than the inner tissue. Nearly 80% of the studied population was unaware of cyanide poisoning, its health effects and how to reduce cyanide content prior to consumption. It is concluded that consumption of raw cassava tubers can lead to undesirable health effects despite of some of them being categorized as sweet. The public should be sensitized on the issues of cyanide in cassava and should avoid consuming raw cassava tubers as preventive measures against cyanide poisoning.
Highlights
Cassava (Manihot esculenta Crantz) is a perennial crop native to tropical America (Allem, 1994) and an important and cheap source of carbohydrate in tropical and sub-tropical regions, in Sub-Sahara Africa
Apart from being a popular staple crop and a superb source of carbohydrates and minerals (Mburu, 2013; Mercola, 2016), cassava carries a potential danger of cyanide poisoning (Babalola, 2014), as it contains cyanogenic glycosides, mainly linamarin: 2-β-D-glucopyranosyloxy-2-methylpropane nitrile, and lotaustralin: 2-β-D-glucopyranosyloxy-2-methylbutyronitrile (Idible, 2006)
Determination of cyanide levels in the sample cassava tubers was done at the Food Science Research Laboratory, Sokoine University of Agriculture (SUA) Morogoro, Tanzania
Summary
Cassava (Manihot esculenta Crantz) is a perennial crop native to tropical America (Allem, 1994) and an important and cheap source of carbohydrate in tropical and sub-tropical regions, in Sub-Sahara Africa. The cassava plant grows faster compares to other crops (Nhassico et al, 2008; Tivana et al, 2014; Ubwa et al, 2015) and has remarkable ability to withstand harsh climatic conditions. These two qualities have made the diverse edible varieties of cassava to be an outstanding crop that saves at least 500 million of human lives from hunger worldwide. Cyanide is responsible for several health complications such as Konzo disease, thyroid goiter and tropical ataxic neuropathy, TAN (Kobawila et al, 2005), incidences of cretinism, stunted growth in children and deaths (Nhassico et al, 2008), epilepsy (Ngugi et al, 2013) as well as behavioral and emotional abnormalities in children (Kariuki et al, 2017)
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