CHAPTER ONE

1.0 INTRODUCTION

1.1 Background Of The Study

Yam (dioscorea spp.) is a multi-species crop that originated principally from Africa

and Asia before spreading to other parts of the world (Hahn et al.1987). It

belongs to the family of dioscoreae within the genus dioscorea and serves as a

staple crop in west Africa.(Asiedu et al. 1992). There are many cultivars of yam

though only six are important as staple foods in the tropics. the economically

important species grown are Dioscorea rotundata(white yam)D.alata (yellow

yam)D.bulbifera (aerial yam) D.esculenta (Chinese yam) and D.dumenterum

(trifoliate yam). Yam tubers which is the most important part of the plants can be

stored longer than other root and tuber crops. This ensures food security even in

times of general scarcity. Yam is the third most important tropical root and tuber

crop after cassava and sweet potato (fu et al. 2005). West Africa is the leading

producer of yam and grows over 90% of the worldwide production (40 tonnes

fresh tuber/year) followed by the west Indians where Jamaica is the leading

producer (FAOSTAT2004). Nigeria is the world’s largest producer of yams

followed by Ghana ivorycoast and togo (FAO2003). Both fresh tubers and yam

flour are now exported from Ghana and Nigeria to developed countries such as

united kingdom and united states of America. These are mostly patronized by

emigrants from growing regions according to the Nigerian export promotion

council (NEPC) Nigeria realized N56 billion in 2007. Sustainable production and

utilization of yam are important steps in enhancing food security and alleviatind

poverty particularly in west Africa where it is estimated to provide more than 200

dietary calories each day for over 60 million people (Nweke et al.1991. FAO

2002).

Yam is consumed in different formsmainly boiledfried or baked.tubers are often

dried and milled into flour for various productboiled yamspoundes yams and

amala are the forms of yam mostly consumed in west Africa especially Nigeria and

benin (Akissoe et al.2001). Yam production faces many constraints among which

are production cost (mainly planting material and labour cost)post-harvset

losses(low yields). Water yam (Dioscorea alata) posses a higher multiplication

ratio and tuber yields as well as better storability than the preferred indigenous

species such as D.rotundata D.alata is popular and prevalent abakaliki agro

ecological zone of ebonyi state Nigeria where it is called ‘Mbala or Noula’ (igbo

names) (Udensi et al.2008) even though D.alata is also eaten boiledit is less

preferred to D.rotundata varieties. D.alata can also be processed into flour and

reconstituted into fufu though generally D.alata contains less sugar and has an

extended shelf-life (Raemackers2001) which ensures availability in times of

scarcity.it is also known for its high nutritional contentwith crude protein content

of 7.4%starch content of 75-84% and vitamin C content of ranging from 13.0-

24.7mg/100g (Osagie.1992).breeders are therefore kein to improve the food

quality of the species as it has good agronomic characteristics.

1.2 STATEMENT OF THE PROBLEMS

The principal problem in yam production that has been identified is the high

cost of seed yam high labour requirement diseases pest as well as high post

harvest losses(Orkwor 1998).another constraint to yam production is the limited

processing technology. About 30% of harvested yam tubers are lost to waste. The

bulkiness of fresh transport and low margins for both farmers and traders are

thus a matter of serious concern in the urban market (Cooke et al.1988).

During the processing of yam through sun-drying methodthe problem

encountered is the loss due to potential contamination of the product variability

in drying time rain damage and so on. Ohweever D.alata fresh texture is usually

not firm as the D.rotundata (white yam) and less suitable than other species for

the preparation of the most popular food product from yam in the west Africa

region(Wireko-manu et al.2011).

Finally during the production of flour from yam in the western part of

Nigeria (the yorubas) the yam flour produced which is called “AMALA” is

normally brownish in colour and dark in nature hence does not have a good

quality and colour. Technologies therefore have been discovered to bring about

the production of yam flour that has a high quality and a good colour and texture.

1.3 OBJECTIVE OF THE STUDY

1.3.0 MOTIVATION

The growing need for the variety of food in Nigeria has become a primary concern

for the urban and rural households in Nigeria. In recent times the concern has

raised much researcher’s interest to do related studies. As reported in many

different studies around the world food security is a common problem.

1.3.1 OBJECTIVES

The present study aims at carryout an experiment on fresh yams optimize the

drying parameters and investigate the effect of drying conditions on the quality of

the yam. To result to this the present study which will address particular issues

food drying could stimulate producers farmers agriculturists educational

practitioners on the phenomenon of drying to enhance the quality of yams to

solve past harvest losses.

1.4 SCOPE OE THE WORK

 To carryout drying experiment on fresh yams and optimize the drying

parameters.

 To determine the effect of drying on the quality properties

 Process the yam samples into chips and carryout approximate analysis of

the fresh and dried samples.

 Production of flour from the yam chips

 Compare flour samples in terms of colour and texture evaluation.