THE ROLE OF A STARTER CULTURE (LATIC ACID BATERIUM) AND SACCHAROMYCES CEREVISIAE IN THE PREPARATION OF AKAMU (ogi or pap)

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 ﾿