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Determination of Hydrogen Cyanide on Twelve Cassava Products

Determination of Hydrogen Cyanide on Twelve Cassava Products

CHAPTER ONE

INTRODUCTION

1.1       Background of the Study

Since the introduction of cassava (Manihot esculenta) by Portuguese traders from Brazil in the 16th century, the crop has over the years become the continent’s most important staple food which is often referred to as the ‘bread of the tropics’.  It belongs to the dicotyledon family, Euphorbiaceae. The Manihot genus is reported to have about 100 species, among which the only commercially cultivated one is Manihot esculenta Crantz. There are two distinct types of cassava plant: Erect, with or without branching at the top type and the Spreading type (Alves, 2002). Presently, no continent in the world consumes cassava more than Africa (Cardoso et al., 2005). However, being the most stable food crop in tropical Africa, its production is of vital importance both from a social and economic perspective according to regional plans of development (Bernardo Ospina et al., 2002). Depending on factors such as custom, local preference and available technology, cassava roots are processed into diverse products such as garri, lafun, fufu, flour, alibo, abacha and others which are consumed widely in Nigeria and other countries in West Africa. It is a crop with primarily high carbohydrate content and low protein content. In the tropical regions, cassava is the most important root crop and a source of energy for human consumption.

Cyanide in cassava exist in three forms such as glucosides (linamarin and lotaustralin), cyanohydrin and free hydrocyanic acid (HCN), they constitute a major limitation to the use of cassava both as food for human and animal (White et al., 2003). The World Health Organization (WHO) has set the safe level of cyanogen in cassava flour at 10 ppm or 10 mg HCN /kg, while in Indonesia the acceptable limit is 40 ppm (FAO/WHO, 2012; Damardjati et al., 2002; Djazuli and Bradbury, 2003; Cardoso et al., 2005), they also have a bitter taste that may function as a feeding deterrent (McKay et al., 2010). Roots and leaves of cassava contain the highest amount of linamarin. During processing, they are hydrolysed by linamerase into acetone cyanohydrin and glucose. Cyanohydrin decomposes spontaneously at ph>5 or at elevated temperature of above 35°C or action of hydroxynitrile lyases into soluble and volatile cyanide ions which are liberated during dewatering, fermentation and roasting operation (Bradbury, 2004; Cliff et al., 2011).

Several hundred different varieties of selected cassava are known and grouped into sweet and bitter varieties depending on the quantity of linamarin present in the tuber. However there is no clear cut difference between the two groups.  Despite all the usefulness of cassava, its use as a food source is limited by its perishability, low protein content and potential toxicity. The consumption of cassava and its derived products which contain large amounts of HCN may be responsible for such visible manifestations as goiter, cretinism and tropical ataxic neuropathy or death (Gueye, 2008). These diseases manifest due to unhydrolysed cyanohydrins associated with sustained intake of insufficiently processed cassava roots (Nhassico et al., 2008; Dufour, 2011). Cyanides are also mitochondrial oxidative phosphorylation blockers and interfere with enzymes and specific organ functions (Bergmann and Keller, 2003).

However, in terms of annual production of food in majority of countries, cassava is the fifth most important food crop after maize, rice, wheat and potato (Jonathan et al., 2013). It is an important source of calories to about 500 million to 1 billion people in tropical countries (Sornyotha et al., 2010).

1.2 Statement of the Problem

            Despite the importance and wide consumption of cassava in Nigeria, little or no effort is being made as to estimate its safety for human and animal consumption. Since cassava contains the potentially toxic cyanogenic glucoside made up of linamarin and lotaustralin. There is the need to assay the concentration of cyanide in these widely consumed cassava products such as Garri, Abacha, cassava flour and cassava cake with respect to WHO permissible standard of cyanide in food.

1.3 Aim

To estimate the concentrations of cyanide in twelve (12) cassava products as to ascertain its cormformance with WHO standard.

1.4       Objectives

  1. To establish the best and reliable cassava product with less cyanide level.
  2. To determine the concentration of cyanide in twelve cassava products: Cassava flour, Dried unprocessed fufu, Processed fufu, Abacha ( Tapioca), Dried abacha, Alibo, Akara akpu, Uwalakande garri, Ikoko garri, Okwo garri, Izzi garri and Red garri.

1.5       Scope

            The determination of cyanide concentration was carried out on Cassava products namely: five samples of Garri viz: Uwalakande garri, Ikoko garri, Izzi garri and red garri; other products include Cassava flour, dried unprocessed fufu, Abacha (Tapioca), Dried abacha, Alibo and Akara akpu (cassava cake).

1.6       Significance of the study

The information gotten from this study ‘determination  of hydrogen cyanide on Twelve  cassava products’ will be essential for public enlightening towards consumers and farmers concerning the need to always go for (prefer) those cassava products which are  safer (non-toxic) to the  health of humans and animals.

CHAPTER TWO

LITERATURE REVIEW

2.1            Origin of Cassava

Cassava (Mannihot esculenta Crantz) is a tropical, perennial plant that originated from Latin America; Its domestication began 5000 – 7000 years BC in the Amazon, Brazil (Allen, 2002). It became popular after the Europeans distributed it to the rest of the world (Henry & Hershey, 2002). Cassava was taken from Brazil to the West coast of Africa by Portuguese navigators in the 16th century (Jones, 2002 & Nweke, 2004), it was brought to East Africa in the 18th century by the Portuguese from Cape Verde and into Mozambique from Zanzibar Island (Leitão, 2003). It was introduced to most of Asia and the Pacific in the late 18th and early 19th centuries (Onwueme, 2002).

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