TABLE OF CONTENTS

Title Page    –         –         –         –         –         –         –         –         –         i

Certification –         –         –         –         –         –         –         –         –         ii

Dedication   –         –         –         –         –         –         –         –         –         iii

Acknowledgment –         –         –         –         –         –         –         –         iv

Table of Contents  –         –         –         –         –         –         –         –         v

CHAPTER ONE

1.0     Introduction           –         –         –         –         –         –         –         1-3

CHAPTER TWO

2.0     Description of Yam         –         –         –         –         –         –         4-5

2.1     Yam Cultivation    –         –         –         –         –         –         –         5-6

2.2     Species of Yam      –         –         –         –         –         –         –         6-10

2.3     Nutritional Benefits of Yam      –         –         –         –         –         10-12

2.4     Health Benefits of Yam   –         –         –         –         –         –         12-13

2.5     Toxicity of Yam    –         –         –         –         –         –         –         13-14

CHAPTER THREE

3.0     Microbial Spoilage of yam        –         –         –         –         –         15-16

3.1     White Yam Rot (Dioscorea rotundata)         –         –         –         16-18

3.2     Diseases of Yam    –         –         –         –         –         –         –         18-19

3.3     Micro Organisms Associated with Yam Spoilage    –         –         19

3.3.1  Rhizopus stolonifer          –         –         –         –         –         –         19-20

3.3.2  Fusarium oxysporum       –         –         –         –         –         –         20-21

3.3.3  Aspergillus niger   –         –         –         –         –         –         –         21-22

3.3.4  Bacillus subtilis     –         –         –         –         –         –         –         22-23

3.3.5  Geotichum candidum       –         –         –         –         –         –         23

3.6     Control of yam rot Diseases       –         –         –         –         –         23-25

CHAPTER FOUR

4.0     Summary and Conclusion

4.1     Summary     –         –         –         –         –         –         –         –         26-27

4.2     Conclusion –         –         –         –         –         –         –         –         27

             References

CHAPTER ONE

1.0     INTRODUCTION

Diseases caused by foodborne pathogens constitute a worldwide public health problem and preventing them is a major goal of societies. Microbiological foodborne diseases are typically caused by bacteria or their metabolites, parasites, fungi, virus or toxins (The International Commission on Microbiological Specification for Foods ICMSF (2006).

Yam (Dioscorea Spp) are root crops which are grown for their edible tubers. They provide the staple carbohydrate food in many parts of West Africa. Nigeria alone produces 21, 814 million tons of yams per year, making it to the world’s largest yam producer (Okigbo, 2004). This region accounts for over 60% of the world yam production. Yam has many importance cultural values attached to it, especially during weddings and other social and religious ceremonies. In many farming communities in Nigeria and other West African Countries, the size of yam enterprise that one has is a reflection of one’s social status. Due to the importance attached to yam, many of these communities celebrate yam festival annually (Awoniyi et al., 2006). Yam is eaten in various forms, cooked or boiled, friend, pounded etc. and is a staple food in the menu of many Nigerians.

Lack of good storage and processing facilities cause a lot of wastage of agricultural produces such as tubers, roots, pulses, fruits and vegetable crops. Specifically, storage is one of the critical problems limiting yam production. According to Okigbo (2004), an estimate of 56% of yam is lost to rot after six months of storage. These loses are due to pathological problems brought about by bacteria, fungi and nematodes (Booth, 1974).

Roots and tubers bruised or otherwise damaged during harvesting may undergo early infestation with moulds and viruses which may in turn lead to rotting. In most countries, several traditional methods of storage are in use. However, losses in these types of storage are in use. However, losses in these types of storage are very high and may be attributed to a number of factors such as: Infestation of yam by scutellonema (Yam nematode), fungi or bacterial rots, rodents, insect, or aflatoxin B, in dried yam chips. Bankole and (Mabekoje, 2004) showed that Aspergillus and Penicillium were the two prevalent genera of fungi, and that the number of colony forming units of the two genera in the yam chips studied exceeded the tolerance limits in foodstuffs specified by the international commission on Microbiological specifications for foods (ICMSF, 1996).