ABSTRACT

This work was aimed at determining the occurrence of aflatoxin producing fungi in three (3) foods: Rice (Oryza sativa), Maize (Zea mays) and Groundnut (Arachis hypogaea) sold in and around Umudike, Abia State, Nigeria. Samples were randomly collected from sellers in three (3) different markets (Umudike, Ahiaeke and Amawom). Serial diluted samples were plated on saboraud dextrose agar using spread plate methods and incubated at 25⁰C for five (5) days, after which fungal growth and mycotoxin production were evaluated using standard method. Results obtained showed the presence of five (5) fungal species: Aspergillus niger, Aspergillus flavus, Penicillum species, Fusarium species and Yeasts. Fungal isolates showed varied occurrence: Aspergillus niger (88.9%), Aspergillus flavus (66.7%), Penicillum (66.7%), Fusarium (44.4%) and Yeasts (100%). The occurrence of A. niger  in foods showed varying occurrence; rice (66.7%), maize (100%) and groundnut (100%), while A. flavus had 33.3%, 66.7% and100% in seeds respectively. The corresponding values for Penicillum were 33.3%, 100% and 66.7% whereas Fusarium recorded 0%, 33.3% and 100% for the same seeds. Yeasts were present in all the samples (100%). The gross occurrence of aflatoxin detected in foods were:  maize (22.2%), groundnut (22.2%) and 0% in rice. The quantitative analysis shows Aflatoxin content ranged 37.76µg/kg to 60.72µg/kg with mean values of 39.80% in maize and 57.01% in groundnut. The variations in the occurrence of fungi, detection of aflatoxin in the seeds and the concentrations of aflatoxin in the foods were noted and it was observed that consumers of these foods are exposed to potential harmful effects. More aflatoxins were in the groundnut than in the maize and rice. Based on the findings, it was therefore recommended that there should be public enlightenment on the incidence of mycotoxins in our foods presently and the high risk associated with it. 

TABLE OF CONTENT

Title page                                                                                                                                i

Certification                                                                                                                            ii

Dedication                                                                                                                               iii

Acknowledgements                                                                                                                iv

Table of contents                                                                                                                    v

List of tables                                                                                                                           vii

List of figures                                                                                                                         viii

Abstract                                                                                                                                   ix

CHAPTER ONE

1.0       Introduction                                                                                                                1

1.1       Aim and Objectives                                                                                                    3

CHAPTER TWO

2.0       Literature Review                                                                                                       4

2.1       Aflatoxin Producing Fungi                                                                                         4

2.2       The Health Implications of Aflatoxins in Humans and Animals                               4

2.3       Food Grains that can be Contaminated with Aflatoxin                                              6

2.4       Major Diseases (Disease Classification) Caused by Aflatoxin Consumption            8

2.5       Factors favourable for the Occurrence of Aflatoxins in Food Grains                        10

2.6       Aflatoxin in Contaminated Maize                                                                              11

2.7       Possibilities of Maize Being Contaminated by Aflatoxin Producing Fungi              14

2.8       Aversion of Aflatoxins in Maize                                                                                15

2.9       Aflatoxin Contamination in Groundnut                                                                    17

2.10     Prevention of Aflatoxins in Groundnut                                                                      18

2.11     Aflatoxin in Rice (Oryza sativa)                                                                                 19

CHAPTER THREE

3.0       Materials and Methods                                                                                               21

3.1       Source of Materials                                                                                                     21

3.2 Sampling, preparations                                                                                                     21

3.2.1 Sampling and sample preparation                                                                                  21

3.2.2 Media preparation                                                                                                          21

3.3       Isolation of fungi contaminants of the seeds                                                              22

3.3.1. Characterization of fungi isolates                                                                                 22

3.3.2. Identification of fungi isolates                                                                                      23

3.4       Determination of aflatoxin                                                                                         23

3.4.1. Extraction of aflatoxin                                                                                                  23

3.4.2 Preparation of thin layer chromatography plate                                                                        24

3.4.3 Detection of Aflatoxin                                                                                                   24

3.4.4    Determination of aflatoxin content                                                                           25

CHAPTER FOUR

4.0       Results                                                                                                                        28

CHAPTER FIVE

5.0         Discussion, Conclusion and Recommendation                                                         33

5.1         Discussion                                                                                                                 33

5.2         Conclusion                                                                                                                 35

5.3         Recommendations                                                                                                     35

References                                                                                                                  36