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Table of Contents

Title page




Table of contents




Background of study

Statements of problem

Significance of study

Scope of study

Aims and objectives

Research questions



Literature review

Species of yam




Methods of yam storage


Nutritional value


Consumption of yam in Africa

Yam flour

Chemical composition of yam flour

Methods of processing yam flour



Materials and methods

Sample collection



Sterilization of materials

Sample preparation

Determination of moisture content of yam samples

Preparation of media

Preparation of Eosin Methylene Blue Agar (EMBA) medium

Preparation of MacConkey Agar medium

Preparation of Manitol Salt Agar medium

Preparation of Sabouraud Dextrose Agar medium

Inoculation of the media

Aerobic Bacteria count using nutrient Agar

Isolation of Bacterium

Identification of isolates





Lists of tables

Table 1: Nutritional value of Yam (raw) per 100g (3.0oz)

Table 2: composition of some Nigeria yam species






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). 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 color from dark brown to light pink (Calverly, 2014). Calverly said “the majority of the vegetable is composed of a much softer substance known as the “meat”. This substance ranges in color from white or yellow to purple or pink in mature yams; there are many cultivars of yam throughout the humid tropics.



  • 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.


  • To make people aware of what they should expect if they insist on consuming commercially prepared yam flour from unhygienic source.
  • 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 and whether they are beneficial or detrimental.


  • To isolate microorganisms from yam flour sold at Eke Oko, Afor Umunze and Eke Awgbu and then identifies the various microorganisms by their names and species.
  • The isolation and identification shall be done by biochemical tests like catalase, citrate, oxidase etc.
  • This project will enligheten the masses that no matter how clean a yam flour may be, it may contain microorganisms if not produced in hygienic way.
  • 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.


  • To isolate and identify 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. Besides, knowledge of the microorganism fauna of yam flours will assist individuals to know the medical consequences of consuming such product.
  • To know how hygienic the commercial yam flour sold can be.
  • To identify and isolate the detrimental microorganisms present in commercially sold yam flour.


  • 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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