Table of Contents
Title page i
Certification ii
Dedication iii
Acknowledgement iv
Table of contents v-vi
CHAPTER ONE
Background of study 1
Statements of problem 2
Significance of study 3
Scope of study 4
Aims and objectives 4
Research questions 5
CHAPTER TWO
Literature review 6
Species of yam 6
Production 11
Harvesting 14
Storage 16
Methods of yam storage 18
Toxicity 20
Nutritional value 21
Phytochemicals 26
Consumption of yam in Africa 26
Yam flour 34
Chemical composition of yam flour 34
Methods of processing yam flour 35
CHAPTER THREE
Materials and methods 39
Sample collection 39
Materials 39
Reagents 40
Sterilization of materials 41
Sample preparation 41
Determination of moisture content of yam samples 42
Preparation of media 43
Preparation of Eosin Methylene Blue Agar (EMBA)
Medium 43
Preparation of MacConkey Agar medium 44
Preparation of Manitol Salt Agar medium 45
Preparation of Sabouraud Dextrose Agar medium 45
Inoculation of the media 46
Aerobic Bacteria count using nutrient Agar 46
Isolation of Bacterium 46
Identification of isolates 47
References 51
Lists of tables
Table 1: Nutritional value of Yam (raw) per 100g (3.0oz) 24
Table 2: composition of some Nigeria yam species 25
CHAPTER ONE
INTRODUCTION
1.0 Background of Study
Yam according to Library Congress, United State of America (2011) “is the common name for some plant species in the genus Dioscorea (family Dioscoreaceae) that form edible tubers. These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa, Asia, Latin-America, the Caribbean and Oceania. There are many cultivars of yam. Although some varieties of sweet-potato (Ipomoea batatas) are also called yam in parts of the United States and Canada, sweet potato is not part of the family Dioscoreaceae but belongs in the unrelated morning-glory family Convolvulaceae”.
Yams are monocots, related to lilies and grasses. Native to Africa and Asia, yam tubers vary in size from that of a small potato to over 60 kilograms. There are over 600 varieties of yams and 95 percent of these crops are grown in Africa. Yams are a monocot (a plant having one embryonic seed leaf) and from the Dioscoreaceae family (Schultheis and Wilson, 2008). Calverly (2014) said “Yam tubers can grow up to 1.5 meters (4.9 feet) in length and weigh up to 70 kilograms (154 lb) and 3 to 6 inches high. The vegetable has a rough skin which is difficult to peel, but which softens after heating. The skins vary in colour from dark brown to light pink the majority of the vegetable is composed of a much softer substance known as the “meat”. This substance ranges in colour from white or yellow to purple or pink in mature yams; there are many cultivars of yam throughout the humid tropics”.
According to Izekor and Olumese (2010), “yam is an important dietary element for Nigerian and West African people. It contributes more than 200 calories per person per day for more than 150 million people in West Africa, and is an important source of income”. They also said “yam is an attractive crop in poor farms with limited resources. It is rich in starch, and can be prepared in many ways. It is available all year round, unlike other, unreliable, seasonal crops. These characteristics make yam a preferred food and a culturally important food security crop in some sub-Saharan African countries”.
1.1 Statement of Problems
- Microorganisms have posed a lot of threat in our society by causing several known or/and unknown diseases. This is majorly noticed from consumption of unhygienic prepared food, which leads to food poisoning, food infection etc.
- As a Microbiologist, this tends to give me a great concern and interest, since there is a high increase rate in the consumption of yam and its products like yam flour.
- It is necessary therefore to isolate and identify microorganisms from commercially sold yam flour especially those from the rural community of Eke Oko, Afor Umunze and Eke Awgbu of Anambra State considering the unwholesome unhygienic manner these flours are prepared using unsterilized tools and water.
- Thus the knowledge of the microorganism fauna of yam flours will assist individuals to know the medical consequences of consuming such product if contaminated.
1.2 Significance of the Study
- To make people aware of what they should expect if they insist on consuming commercially prepared yam flour from unhygienic
- To remove fear from yam flour consumers as to whether the yam flour usually bought is free from microorganisms or not.
- To know whether the commercial yam flour has microorganisms and if it does, to know the species.
- This project will enlighten the masses that no matter how clean a yam flour may be, it may contain microorganisms if not produced in hygienic
1.3 Scope of Study
- The isolation and identification shall be done by biochemical tests like catalase, coagulase, indole etc.
- The isolation and identification period will not be more than 48-72hours so as to get the right results. After the isolation and identification process, we may get microorganisms free commercial yam flour or vice versa.
1.4 Aims and Objectives
- To know how hygienic the commercially sold yam flour can be.
- To isolate some of the microorganisms associated with yam flour especially those ones sold commercially in the market in Eke Oko, Afor Umunze and Eke Awgbu of Anambra State considering the unwholesome unhygienic manner these flours are prepared using unsterilized tools and water.
- To identify the various microorganisms by their names and species.
- To make people aware of what they should expect in commercially sold yam flour without packaging.
1.5 Research Questions
- What are the compositions of yam flour?
- What are the benefits of consuming yam flour?
- Could there be microorganisms present in yam flour sold at Eke Oko, Afor Umunze and Eke Awgbu?
- What will be the solution to any problem discovered?
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