Determination of Hydrogen Cyanide in Cassava

ABSTRACT

Cassava is one of the major dietary staple for a large percentage of the population of tropical Africa and other parts of the world, and is likely to remain the biggest single source of calories for the poor in the continents. An important drawback to increase cassava use for human and animal feeding is its cyanogenic potential, or ability to generate hydrogen cyanide, a well – known poison with potential acute and chronic metabolic effects in human.

This project work deals with the determination of hydrogen cyanide (HCN) concentration in cassava tubers (using the bitter varieties) collected from Institute of Management and Technology (IMT) premises with respect to four days fermentation period using Atomic Absorption spectrophotometer (AAS).

The result shows that the concentration of hydrogen cyanide (HCN) decreases with increase in fermentation period, and based on the safe limit given by the us food and drug administration (FDA) and others, a safe fermentation period for cassava before processing it to produce garri is deduced.

CHAPTER ONE

INTRODUCTION

Cyanide, is usually found in compounds. It can interact with metals and other organic compounds. Cyanide refers to all of the cyanide compounds that can be determined as the cyanide ion, CN. The cyanide ion is a conjugate base of a weak acid, hydrogen cyanide, which is an extremely poisonous gas with an almond odor. Other forms of cyanide compounds are sodium cyanide (NaCN) and potassium cyanide (KCN). Cyanide can be produced by certain organism (e.g bacteria, fungi and algae), and equally present in plants. Cyanide ion is one of the most rapidly working poisons. Lethal doses taken orally act in minutes, cyanide, poisons by asphyxiation, as does carbon monoxide, but the mechanism is different. Instead of preventing the cells from getting oxygen, cyanide interferes with oxidative enzymes, such as cytochrome oxidize, which is vital to every cell in use of oxygen. Oxidizes are enzymes containing metal usually iron or copper. Cyanide binds tightly to the enzyme cytochrome C and forms stable cyanide complexes with Fe3+ ion and inactivates the enzyme system.

Much of the cyanide in soil, water and air comes from industrial processes gold mining, waste waters from starch industry. The major source of cyanide in water are discharges from metal mining processes, other sources include exhaust, release from certain chemical industries, municipal waste burning and use of pesticides containing cyanide. Underground water can be contaminated by cyanide present in landfills. In other body, cyanide can combines with plants foods including almonds, millet sprouts, lima beans, soy spinach, bamboo shoots and cassava roots, cyanide occurs as part of naturally occurring sugars or other complex organic compounds.

1.1 HYDROGEN CYANIDE

Chemical formular: HCN

Synonyms: Hydrocyanic acid, prussic acid, formonitrile, carbon hydride nitride

Hydrogen cyanide (HCN) was discovered by Scheele in 1982. He made it by heating sulphuric acid with Prussian blue; hence the old name was prussic acid. HCN occurs in nature as glycoside amygdalin in some plants, for almonds, cassava etc. Hydrogen cyanide together with sodium cyanide and potassium cyanide are the most of cyanide likely to be found in the environment as a result of industrial activities. Its presence could be found in air, water, soil, and even in gaseous state (present in solution in cassava root), with a faint, bitter, almond like odour. It is a potential metabolic poison present in some food crops and other plants.

Hydrogen cyanide is a small molecule composed of a carbon, hydrogen and nitrogen atom joined together by a stable triple bond. This poison is best known for its inhibition of many enzymes that are important in animal metabolism. Enzymes are proteins that act as catalyst in biochemical reaction.

It could be made to act as an anti-herb ivory compound to discourage plant consumers (pests). Most often, it attaches itself to other molecules in the form of cyanogenic glycosides. In example of one such compound is amygdalin (from stems of cherry, apricot etc). In this form, cyanide is non-toxic to the plant, only in the breakdown of cyanogenic glycosides, during animal consumption or digestion, is hydrogen cyanide released. For example, cows feeding on some species of grasses containing cyanogenic glycosides became ill as they chew on the grass, in this fashion, it is hypothesized that cyanide in non lethal does effectively deters herbivory.

Some cyanide containing plants are listed below (plants and relative cyanide level):

  • Cassava (+ + + +)
  • Lima beans (+ + +)
  • Sorghum (+ +)
  • Millet (+ +)
  • Bamboo Shoots (+ +)
  • Sweet Potatoes (+)
  • Maize (+)

1.2 AIMS AND OBJECTIVES OF THE STUDY

The aim of this project is to determine the effect of fermentation period (time) on hydrogen cyanide concentration in cassava tubers and to suggest safe and efficient processing technique of cassava in order to reduce hydrocyanic acid concentration thereby enhancing the consumption of cassava without health hazard.

1.3 STATEMENT OF PROBLEM

Since high concentration of hydrogen cyanide is fatal to human and other life species especially when consumed and is lethal to the body system or dangerous to health, the problem lies on how to reduce this high concentration to a certain limit or how its concentration could be eliminated.

1.4 HYPOTHESIS

H0: Unfermented cassava tubers creates or causes health hazards such as dysentery, running stomach etc after consumption.

H1: After fermentation, the high concentration of hydrogen cyanide which limits the consumption of cassava due to its hazardous effects was found to be reduced to non-toxic effect in the system of the consumers.

1.5 SCOPE OF STUDY

This study deals on the laboratory test to determine the concentration of hydrocyanic acid content in cassava. The effect of fermentation time on the cyanide concentration is discussed and the application of this study is only limited to economic aspect of cassava processing to produce a cyanide free garri, which of course, is a stable food in Enugu State.

The study do not deal on the evaluation and analysis of hydrogen cyanide in air and soil. Medical effects of hydrogen cyanide on health are discussed and detail process of how its attack on health is not included in this study.

The safe and efficient processing technique to reduce hydrocyanic acid content in Garri is only applicable to the varieties of cassava found in Institute of Management and Technology (IMT) Enugu Premises.

There are many traditional methods used around the world to process cassava tubers into Garri, such as sun drying, Heap fermentation and soak – in – water fermentation, but reference and discussion in this study is on all the methods but the specific method applied in this study is fermentation by soaking in water for days.