Cassava is a major staple root crop in many developing countries. It is an important source of energy and a nutritionally strategic famine crop in areas of low rainfall. Mature cassava roots can survive for long periods without water while still retaining their nutritional value. The crop also requires low input of labour, cash and time.

Roots of cassava are a valuable source of calories, containing 80-90% of carbohydrate (dry basis) but have low contents of lipids, minerals and proteins. The protein content and amino acids profile of cassava leaves are comparable with those of eggs, and the leaves are rich in the minerals iron, zinc, magnesium, manganese and calcium, as well as vitamins B1, B2 and C and carotenoids. A diet of both cassava roots and leaves could provide almost complete nutritional needs, if a secondary source of essential sulfur-containing amino acids is supplied, due to the lack of cystine and methionine in cassava roots and leaves.

However, cassava also contains toxic and antinutritional components that can interfere with digestion and nutrient uptake. These include cyanogenic glucosides (linamarin and lotaustralin), cyanohydrins and free cyanide. Long-term consumption of small amounts of cyanide can cause severe health problems such as tropical neuropathy, glucose intolerance and, when coupled with low iodine intake, goitre and cretinism. Antinutrients such as phytate and polyphenols can reduce nutrient bioavailability, but may also act as anticarcinogens and antioxidants depending on the amount ingested.

In a paper by Montagnac et al.¹, traditional methods used to reduce cassava toxicity and contents of selected antinutrients are described. These include boiling, steaming, baking, frying, drying, fermentation, steam distillation and/or starch production. Effects of these methods on reducing cyanide, phytate and polyphenols contents of cassava leaves and roots were examined. The review shows that the various traditional methods are relatively effective in removing cyanide from cassava, particularly those involving grating and crushing. The removal efficiency appears to depend on the duration of processing; however, many small-scale farmers in developing countries did not always have the time required to adequately process cassava. Processing partly removed phytate and polyphenols, but could also reduce nutritional value.

1 Montagnac, JA; Davis, CR; Tanumihardjo, SA (2009). Processing techniques to reduce toxicity and antinutrients of cassava for use as a staple food. Comprehensive Reviews in Food Science and Technology 8 (1) 17-27

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