ABSTRACT

Ogi is a traditional fermented food produced from maize and serves as breakfast foor the majority of the population and is a good food choice for the sicks. This study was carried out to develop an appropriate starter culture for its controlled fermentation in order to improve the safety and quality of the product. In this work, starter cultures of Lactobacillus brevis, Lactococcus cremoris and Saccharomyces cerevisiae were used to prepare ogi hence comparing it with the spontaneous type. The lactic acid bacteria (LAB) and yeast were isolated from nunu and palmwine using de Mann Rogosa and Sharpe (MRS) agar and Sabouraud Dextrose Agar (SDA) respectively. A suspension of the organisms was made from their pure isolates after sub-culture before inoculating into the fermenting vessels containing the sterile ogi. The maize samples were fermented for three days and physico-chemical and microbiological changes was determined during the fermentation. The lactic acid bacteria (LAB) and yeast involved during the fermentation of maize for the production of ogi were quantified. (ANOVA, P=0.05) indicated the significant difference between the physic-chemical parameters and the sensory evaluation test. There was significant drop in the final pH values of the four preparation from 5.54 to 4.31. Mean while respective titratable acidity (TTA) increased on average from 0.03 up to 0.09g/L. The total viable count of bacteria increased from 4.2x 105 to 1.28x106 while the total fungal count increased within narrow ranges from 3.2x 105 to 6.1 x 105. This work showed that ogi prepared with the LAB and yeast (starter culture) fermented within three days of the fermentation compared to the traditional spontaneous one as it ranked highest with regard to sensory evaluation and received overall acceptability of 7.

TABLE OF CONTENTS

Title page i

Certification page ii

Dedication

Acknowledgements iv

Table of contents v

List of Tables

Abstract ix

CHAPTER ONE

1.0    INTRODUCTION

1.1 Ogi Production and Consumption 1

1.2 Aims and Objectives 4

CHAPTER TWO

2.0 LITERATURE REVIEW

2.1 Maize   Grain 5

2.2  Traditional Fermented Cereal-Based Foods in West Africa 6 

2.2.1 Ogi

2.2.2 Abolo

2.2.3 Banku

2.2.4 Koko

2.3 Starter Culture

2.3.1 Moulds

2.3.2 Yeasts

2.3.3 Bacteria 12

2.4 Attributes of Starter Culture 13

2.4.1 Desirable Properties of Starter Culture 13

2.5 Starter Cultures in Africa Cereal Fermentation 14

2.5.1 Use of Starter Cultures in Maize Fermentation 15

2.5.2 Use of Starter Cultures in Ogi Preparation 16

2.6    Lactic Acid Bacteria 17

2.6.1 The Role of Lactic Acid Bacteria in Fermentation 18

2.6.2 Microorganisms Involved in the Lactic Acid Fermentation 20

2.7 Methods used for the identification of lactic acid bacteria 23 

2.7.1 Conventional Taxonomy 23 

2.7.2 Numerical Taxonomy 24

2.7.3 DNA Based Techniques 24

2.8 Role of Yeasts in Maize Fermentation 25

2.8.1 Saccharomyces cerevisiae 26

2.8.2 Candida krusei 26 

CHAPTER THREE

3.0 MATERIAL AND METHODS

3.1    Materials 28

3.2    Preparation of the starter cultures 28

3.3 Characterization of Bacterial Isolates 29

3.3.1 Gram Staining 29

3.3.2 Biochemical Test 29

3.4    Preparation of Inoculum for Controlled Fermentation  30

3.5    Preparation of Ogi Using the Starter Culture 30

3.6 Microbiological Counts 30

3.7 Measurement of pH of the Ogi Samples 31

3.8 Measurement of Total Titratable Acidity (TTA) 31

CHAPTER FOUR

4.0 RESULTS

4.1 Morphological and Biochemical Characteristics of the Bacteria Isolates 32

4.2 Microbial Load of Ogi Samples during Fermentation 32

4.3 pH And Titratable Acidity of Ogi during Fermentation 32

4.4 Sensory Evaluation Test (Organoleptic Characteristics) 32

CHAPTER FIVE

5.0 DISCUSSION, CONCLUSION AND RECOMMENDATIONS

5.1 Discussion 39

5.2 Conclusion and Recommendation 42

References 43

LIST OF TABLES

TABLE                            TITLE                                                                                PAGE

2.1 Traditional Lactic Acid Cereal- Based Fermented Foods and Beverages 30

4.1       Morphological and Biochemical Characteristics of the Bacteria Isolates 24

4.2 Microbial Load of Ogiduring Fermentation 25

 4.3 pH and Titratable Acidity Values of Ogi during Fermentation         26

4.4 Sensory Evaluation Test 27