Determination of Cyanide Contents in Cassava
CHAPTER ONE
AIM OF THE STUDY
The aim of the study is as follows:
- To estimate the rate of cyanide in three cassava varieties.
- To assess some cassava detoxification processes.
CHAPTER TWO
LITERATURE REVIEW
CYANIDE TOXICITY
Cyanides are extremely toxic to terrestrial vertebrates and aquatic life. The cyanide anion is an inhibitor of the enzyme cytochrome C oxidase (a trans-membrane protein complex found in mitochondria and bacteria), attaching to the Iron within this protein and preventing the transport of electrons from enzyme to oxygen. Consequently, the eukaryotic cell can no Longer aerobically produce ATP for energy and cellular respiration is greatly reduced, affecting those tissues most dependent on, especially the central nervous system and the heart, Haque, (2002).
EFFECT OF CHRONIC EXPOSURE TO CYGANOGENIC GLYCOSIDE CONTAINING FOOD STUFFS.
Liberation of hydrogen HCN from cyanogenic glycosides (CNG) usually occurs after mastication and ingestion and arises from enzymatic degradation of the latter to produce HCN, resulting in acute or chronic cyanide poisoning. The enzyme responsible (β-glucosidase) may arise from the plant material or from gut microflora. HCN can also be produced to a lesser extent by glucosidases in the liver, Lindsary et al, (2004).
Chronic exposure to food containing CNGs has been linked to several diseases primarily affecting the central nervous system, Tropical ataxic neuropathy (TAN) describes several neurological symptoms affecting the mouth, eye sight, hearing and gait that present clinically as sore tongue, optical atrophy, angular stomatitis (inflammatory lesions at corners of the mouth), neurosensory deafness, skin desquamations (Peeling or shedding of outer skin Layers) and sensory gait ataxia (deviation from normal walking).
Goitre and cretinism attributed to iodine deficiency can be exacerbated by chronic consumption of inadequately processed cassava. Cyanogenic glycosides are converted to thiocyanate during the detoxification process, which reacts with iodine which is subsequently unavailable to the thyroid, increasing the dietary requirement for lodine, Zhanga, et al, (2005).
CHAPTER THREE
MATERIAL AND METHODS
EXPERIMENTAL DESIGN
Freshly harvested cassava roots of local variety (Nwangbisi and Kombo) from a village farm in Amorji-Nike were used to carry out the experiment.
Cassava –derived products such as cassava chips, cassava flour and Garri were also used.
PREPARATION OF DERIVED PRODUCT
The preparation of derived products was performed by me. The different products are:
Cassava chips:
Fresh cassava was pealed manually with kitchen knife, washed, cut into small pieces and dried.
Cassava flour:
For cassava flour, the tubers were peeled washed, grated and pressed to extract the remaining Juice. After pressing, the cassava compact blocks were grinded and sieved into flour to remove the waste, then sun dried to reach a moisture content of 12 percent.
Garri
Fresh cassava was peeled, washed, grated into small pieces and fermented for two days. The product obtained was then pressed. The pulp was grinded, sieved and roasted with a garri roasting pan to reach a moisture content of 10.5 percent.
CHAPTER FOUR
RESULTS AND DISCUSSION
TOTAL CYANIDE CONTENTS IN CASSAVA SLICES (1/4, ½ ¾) AND VERITIES
Statistical analysis showed that: For fixed principal factor (slice type). Fisher calculated (Fcal) < fisher read (fre). We accept Ho. Total cyanide contents in cassava slices showed no significant difference:
For the random accessory factor (variety types fcal > Fre, Ho rejected). Total cyanide contents in cassava verities were significantly different.
The total cyanide contents in different slices and cassava varieties from the first batch are presented in table I. Result showed the significant difference between cassava varieties (P < 0.05). Total cyanide contents did not differ in each slice. Kombo variety presented the lowest total cyanide content in each slice. The significant difference between total cyanide contents in cassava varieties obtained in this study it consistent with the patterns reported and found by a significant difference between HCN concentrations in cassava varieties. Based on the total cyanide contents, cassava can be classified into three groups as follows: Sweet varieties (< 50mg/kg), intermediate varieties (50-100mg/kg) and bitter varieties (> 100 mg/kg). In view of my results I could say that the cassava varieties studied would be bitter, due to their high level of cyanide contents. The reduction of cyanide content would be important to make these products agreeable for consumption.
CHAPTER FIVE
CONCLUSION
This study revealed that the total cyanide contents in cassava roots were higher than 100mg HCN/kg and these cyanide contents varied in cassava varities. I established that the methods of cassava processing were able to reduce total cyanide contents in cassava roots. Moreover, garri and cassava flour prepared from Kombo and Nwangbisi varieties showed the residual cyanide content below the level of 10mg HCN/kg that is considered safe. These results may be used on household and cottage –industry to ensure food safety.
RECOMMENDATION
According to the result obtained during the processing of some cassava derived products showed that the presence of HCN is at low concentration than in the fresh cassava root which is more tolerable in human system.
It is good that all the steps involved in cassava derived products are observed as it helps to degrade tine cyanogenic compounds which when consumed by humans at high concentration may lead to the development of the following diseases like; goitre, cretinism and may even cause death.
It is recommended that before consuming a cassava derived products ensure that all the processes that causes detoxification of cyanide in cassava was carried out.
REFERENCES
- Haque, M.R., Brad Bury, T.H., Food Chemistry 2002 (1). 107 -114.
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- M.H. Bradbury “Processing of Cassava to Reduce Cyanide Content”. Cassava Cyanide Disease Network News (CCDN), 3:3-4,2004.
- Ernesto, A.P Cardoso, J, Cliff, S.V Egan and J.H. Bradbury, “CYanogenic Potential of Cassava Flour: Field trial in Mozambique of a simple Kit”. International Journal of Food Sciences and Nutrition, 49:93-99,1998.
- Ernesto, A.P. Cardoso, E Mirone, F. Massaza, J. Cliff, R.M. Haque and H.J. Bradbury, “Processing of Cassava Roots to Remove Cyanogens”. Journal of Food composition and Analysis, 18: 451-460, 2005.
