COMPARATIVE PROXIMATE COMPOSITION AND CYANOGENIC GLUCOSIDE CONTENT OF PROCESSED CASSAVA (GARRI)

CHAPTER ONE

INTRODUCTION

1.1  Background of the Study

Cassava (Manihot esculenta Crantz) is an extensively cultivated cash crop grown for its starchy root, and it is the third largest carbohydrate food source within the tropical regions, after rice and corn (ceballos, Iglesias, Perez and Dixon, 2014). It is grown throughout the tropics and could be regarded as the most important root crop grown in terms of total production (Ezebuiro, Chukwu, Okoye and Oboagju, 2014). Cassava roots are highly perishable and cannot be kept in fresh condition for more than a few days without deterioration in quality. In order to extend the shelf life of the roots, cassava is processed into dried products to meet the local needs, taste and tradition for use and storage. As a result of this, cassava roots can be processed into various products such as fufu, tapioka, chips, elubo and garri (Bokanga, 2011).

Garri is one of the most popular forms in which a processed cassava tuber is consumed. It is also the most common form in which cassava is sold in Nigeria and in many other African countries (Oluwole, Olatunji and Odunfa, 2011). Garri is a convenient food with short preparation time especially for commercial demand, it’s cheapness, ease of storage and preparation for consumption. These characteristics combine to mate it a purchasable preference, and a consumable food product among the rural and urban dwellers in Nigeria, as well as in other West African countries and even to an extent, Africa as a whole.

As a versatile cassava product, garri can be utilized in a variety of ways; it can be soaked in cold water and consumed directly with some light accompaniment such as sweeteners, fish and groundnut. Recent studies have shown that garri is widely consumed as food in several parts of Nigeria (Harbour and Ogundu, 2015). Garri can be eaten dry or soaked in water as “eba” and consumed with soups and stews (Oyewole, 2010; Ajao and Adigun, 2015). It is a staple food which is processed by millions of people in West Africa, where it forms a significant part of their diet (Ogiehor and Ikenebomeh, 2015).   

In Nigeria, garri produced are of different types depending on the state or geographical region where it is produced. “Ijebu” garri is produced in Ijebu-ode and it is commonly eaten by the people in the Western part of Nigeria. “Bendel” garri is produced and commonly eaten by the people in the Mid-Western Eastern part of Nigeria. These types of garri maybe easily recognized and differentiated by their colour, and taste (Asante-Pok, 2013). Garri commonly consumed in Akwa Ibom State are Bendel, Okrikang and Atam garri. Bendel garri is commonly produced by the Delta and Edo people, and it is consumed in the Eastern part of Nigeria. Okrikang garri is commonly produced and consumed in Akwa Ibom State. Atam garri is commonly produced in Cross River State and is consumed in both Akwa Ibom and Cross River.

Production of garri can be done mechanically or traditionally. The process involves harvesting of cassava roots, peeling, washing, grating, pressing, fermentation, sieving, frying, cooling, packaging and storage (IITA, 2015). Market expansion for garri to some extent depends largely on the degree of which the quality of the processed garri can be improved upon to make it attractive to the potential consumers. Whether garri type can be relied upon as a staple food, will to a large extent depend on its cost, texture and colour. Garri, during processing may be fortified by adding palm oil, sweet potato, among others (Subukola, Akinpelu and Awonorin, 2010) to enhance acceptability and reduce cost. Howbeit, garri which is not properly processed is exposed to toxicity from cynaogenic glucoside. The presence of cyanogenic glocoside (linamarin and lotaustralin) constitutes a major danger to the use of garri as a human food. These glucosides in any garri will readily breakdown to give hydrogen cyanide by an enzyme called linamarase (Asegbelohin and Onyimonyim, 2015).

The traditional methods of processing cassava have been found to be efficient in reducing the amount of residual cyanide in the product (Achinewhu and Onwuamanam, 2011). However, if processing of garri is inadequate and such garri is consumed in large amount, cyanide poisoning may occur. This may lead to visible manifestations of goiter, cretinism, tropical ataxic neuropathy and konzo (paralysis of the limbs) which are adverse effects of cyanogenic glucoside consumption in garri (Zuraida, Widayat and Hannarida, 2012). Therefore, there is need to evaluate the health implication of garri sold and consumed in Osun state by determining the cyanogenic glucoside content of such garri and their nutrient potentials.