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East African scientists push cassava preservation to remove poisonous cyanide

East African scientists are pushing for the third and safest way of removing cyanide, the poisonous component in cassava, which goes beyond peeling and harvesting to fermenting and milling, instead of doing away with cyanide-laden varieties that are more drought-resistant.

Cassava is among the staple foods in East Africa providing some 85 million East Africans with food and income. But the crop is heavily laden with cyanide, a poisonous compound which if not well dried can lead to death. And it has. Farmers oblivious of the right dried mechanisms either dry the crop partially which doesn’t remove the cyanide completely. But even with drying, traces of cyanide can still be found.

It is this quagmire that has seen scientists root for new varieties that are cyanide free. But trying to sell them to farmers has proven hard. First because the old varieties have been stuck with farmers for long and secondly because new varieties don’t have superior drought resistant traits as does the traditional ones.
Local scientists have therefore resulted in pushing for the safest way of riding the traditional cassavas from any trace of cyanide.

Speaking in Kampala at the third Cassava Regional Center of Excellence Review and Scientific Conference, Dr. Nuwamanya Ephraim from Uganda’s National Crop Research Resource Institute (NACRRI) noted that although the cassava varieties with high cyanide content is being eliminated from households through adoption of the elite varieties that are safe for consumption, a number of factors are still hindering the success of this initiative. “Some communities in East Africa still hold onto these varieties due to the need for food security. The bitter varieties with high cyanogen content are more stress tolerant and can flourish even in extreme weathers conditions like drought thereby being the only source of food for communities during such periods,” explained Nuwamanya.

In Uganda, these varieties include Tongolo in Northern Uganda, Kalinga and Rutuba in Western Uganda. Nevertheless, a number of ways are being adopted in order to enhance farmers in the cassava growing areas which include adoption of new varieties coupled with information on how to make the ones with high cyanide content safe for consumption.

The need to empower the locals with the right information on how to process and ensure that cassava meals are safe is already in the process with a team of stakeholders from NACRRI taking the lead. Primary and secondary processing alone does not rid the high cyanide levels from the bitter varieties and hence the need for tertiary processing. Primary processing according to Dr. Nuwamanya is the harvesting, peeling, chopping and cooking which still leaves the plant toxic. Drying and milling which Dr. Nuwamanya refers to as the secondary processing reduces cyanide content but still leaves its high toxic levels. It’s only tertiary processing which rids the toxins from the crop.

Tertiary processing entails peeling the crop and fermenting it for longer periods of about seven days instead of the normal two. After drying the crop after fermentation, one then mills it. The final stage of ridding cassava from the toxins is the heating of the flour before using it to either make porridge, posho, or cakes. “In most cases, families ignore these processes due to lack of knowledge and a times this ignorance result into deaths hence the need to disseminate the information to them on due procedure,”

Dr. Nuwamanya further explained that cyanide scientifically is carbon bonded to Nitrogen. Heating of the cassava breaks the bond attaching carbon and Nitrogen letting them be free elements that are in these case non toxic. Similarly, Fermenting exposes cassava to water and thus forming Hydro cyanide which is volatile and eventually evaporates.

For any crop with cyanide content to be safe for consumption, Dr. Nuwamanya advised that it should have below 100 parts per million of cyanide content.  “With such level, any simple processing ensures that the food is safe for consumption.” However, some of the cassava with higher contents of the toxin have over 100 parts per million making it hard for the ridding of the cyanide. The recommended World Health Organization levels are 50 parts per million while East Africa’s standard demands for 10 parts per million.

Cyanogenous cassava poses a threat for over 500 million people who rely on cassava as their main source of calories, among them subsistence farmers in Sub-Saharan Africa. “In Africa, improperly processed cassava is a major problem. It’s associated with a number of cyanide-related health disorders, particularly among people who are already malnourished,” explained Dr. Nuwamanya.

Chronic, low-level cyanide exposure is associated with the development of goiter and with tropical ataxic neuropathy, a nerve-damaging disordaer that renders a person unsteady and uncoordinated. Severe cyanide poisoning, particularly during famines, is associated with outbreaks of a debilitating, irreversible paralytic disorder called Konzo and, in some cases, death. The incidence of Konzo and tropical ataxic neuropathy can be as high as 3 percent in some areas. People who get little or no protein in their diets are particularly susceptible to cyanide poisoning, as they lack the proper amino acids necessary to help detoxify the poison.

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