Cassava (Manihot esculenta) has the common name such as cassava, Brazilian avoowool, manioc and tapioca is a woody shrub of the spurge family, Euphorbiaceae, native to South America. It is extensively cultivated as an annual crop in tropical and sub-tropical regions for its edible starchy tuberous root, a major source of carbohydrate. Though it is sometimes called Yuca in Spanish, it differs from the Yucca an unrelated fruit bearing shrub in the family Asparafaceae cassava. When dried to a powered (or barely) extract is called tapioca, it’s fermented, flaky version is named garri.
Cassava is the third largest source of food carbohydrate in the tropics, after rice and maize. Cassava is a major staple food in the developing world, providing a basic diet for over half a billion people. It is one of the most drought tolerant crops capable of growing on marginal soils. Nigeria is the world’s largest producer of cassava, while Thailand is the largest exporter of dried cassava.
CLASSIFICATION AND TOXICITY OF CASSAVA
Cassava is classified as either sweet or bitter like other root and tuber crop. Both bitter and sweet varieties of cassava contain anti-nutritional factors and toxins, with the bitter varieties containing larger proportion. They must be properly processed before consumption as improper preparation of cassava can leave enough residual of cyanide to cause acute cyanide intoxication goiter and even ataxia (shaky movement and unsteady gait that results from the brains failure to regulate the body’s posture and the strength and direction of limbs movement) or partial paralysis.
The more toxic varieties of cassava are a fall-back resources (a food security crop) in times of famine in some places. Farmers often prefer the bitter varieties because they deter pests, animals and thieves.
RISK OF POOR GARRI PROCESSING
Garri production involves processing raw cassava after harvesting from the farm. The major processes involving pilling of cassava bark, washing, 24-30 hours of fermentation(fermentation here occurs in small percentage), grinding in the cassava mill, compression to dehydrate using a compressor machine, then the final stage would now include sieving with aluminum sieves with hole diameter of 0.2-0.4mm and frying on a plane fry pan at temperature of about 90O-100Oc.
However, these days because of increased demand of garri, the pain-taking processing procedures as highlighted above are by-passed. Thus, leading to poor finished product containing some reasonable amount of anti-nutritional factor such as cyanide and its potential effect. Poor processing lacks fermentation process of at least 24 hours and processing process is dependent on heat for the removal of cyanide. It is important to state here that, the incomplete detoxification often result due to the fact that the temperature needed for complete detoxification might not be attained.
DETOXIFICATION OF GARRI
Garri is commonly detoxified of Hydrogen Cyanide (HCN), fermentation (destroys cyanide linkages & bonds), application of palm oil (functions as an emulsifiers, it emulsifies the hydrogen cyanide converting it to harmless state.)
DETOXIFICATION IN HUMAN
In human, HCN is detoxified with rhodanase forming a goiterogenic compound thiocyanate which is excreted in urine. This process requires sulphur donors such as dietary sulfur containing amino acid.
The major reactions involved in detoxification of ingested cyanide include:
Reaction with cysteine to form Iminothiozilidine compound that is excreted through saliva and urine.
Minor amounts may be converted into formic acid and excreted in urine.
Cyanide may combine with hydroxyl cobalamine and excreted in urine and bile.
Hence, the detoxification of HCN is influenced by the nutritional status such as B. vitamins like B12, folic acid and essential sulfur containing amino acids provided by dietary good quality protein.
SYSTEMIC EFFECT OF GARRI NOTABLY ON THE NERVOUS SYSTEM
This compound is known to limit the ability of thyroxin gland to store and process iodine. The goiteroforic effect of thiocyanate may also lead to endemic goiter. The effect of thiocyanate may also lead to endemic goiters. The effect of iodine deficiency can be devastating robbing the next generation of brain power and productivity. The impairment in thyroid function may also lead to alterations in other metabolic pathway especially lipids.
It is of worthy note to say that the method of garri production and method of consumption could determine the extent of cyanide toxicity from garri. The most common effect noticed in our day-long consumption of garri (i.e. drinking form) has always been headaches, eyes irritation, breathing difficulties and depressed heart rate. Garri processing should therefore include at least 30 hours fermentation and adequate heat during frying of the garri product, during the final production process.
However, if garri is to be consumed in a form of snacks, rich source of Hydroxycarbon amine (VB) should be included milk a cheap source of vitamin B12. These precautions would however, go a long way in preserving the brains of our next generation and also reduce the risk of thyroidism or goiter.
Article credited to Victor Moses.