ABSTRACT  

This study was to determine the microbiological and biochemical changes during fermentation of sorghum bicolor using Saccharomyces cerevisiae. The bacteria species isolated from the fermented sorghum samples, were identified based on their morphological characteristics, pigmentation on media, microscopy, biochemical and sugar fermentation methods while the yeast (Saccharomyces cerevisiae) used for the fermentation of sorghum was isolated using pour plate technique on Sabouraud Dextrose Agar (SDA). This study revealed that mean viable microbial counts varied as the time of fermentation increased. However the viable counts on the fermented sorghum sample were seen to decrease from the fermentation period of 0 hours to fermentation period of 72 hours. The total viable counts on Lactic acid bacteria revealed more counts (6.4x108) at the end of fermentation period (72hours) compared with single cultures. The physical analysis of the fermented sorghum samples in this study also revealed that pH, Temperature and Titratable acid slightly increased by fermentation interval from 0 hour to 72 hours of fermentation respectively. The proximate composition of the fermented sorghum samples revealed that the moisture content, crude fiber, crude protein and crude fat of the samples were high, and This study also revealed Lactobacillus spp as being the most widely distributed and frequently occurring isolates with a high percentage occurrence of 7(42.27%) while Saccharomyces cerevisiae 4(24.26%) was the most widely distributed among fungal species. this could improve the nutritional quality of sorghum. Therefore, the results reported could serve as a starting point to understand the microbiological and biochemical processes in the fermentation of sorghum using Saccharomyces cerevisiae with the aim of improving the efficiency of the process.

TABLE OF CONTENTS

Title Page i

Certification iii

Dedication iv

Acknowledgement v

Table of Contents vi

List of Tables viii

Abstract ix

CHAPTER ONE

1.0 Introduction 1

1.1 Aim and Objectives 3

CHAPTER TWO

2.0 Literature Review 4

2.1 Sorghum 4

2.2 History of Fermented Foods 4

2.3 Fermentation of Foods 5

2.4 Fermentation Process 6

2.4.1 Natural Fermentation 6

2.4.2 Back Slopping 7

2.4.3 Controlled Fermentation 7

2.5 Alcoholic Fermentation 7

2.5.1 Traditional Alcoholic Beverages 8

2.6 Types of Fermented Cereal Foods 9

2.6.1 Tarhana 9

2.6.2 Togwa 9

2.6.3 Ogi 9

2.6.4 Yosa 10

2.6.5 Balao balao 10

2.6.6    Burukutu 10

2.7 Microorganisms Involved In Fermentation Process 11

2.1 Lactic Acid Bacteria 12

2.2 Fermentation by Lactic Acid Bacteria Homofermentation and Heterofermentation 12

2.3 Taxonomical Classification of Lactic Acid Bacteria 13

2.4 General Position of Specific Lactic Acid Bacteria 13

2.4.1 Lactobacillus 13

2.4.2 Streptococcus 14

2.4.3 Pediococcus 14

2.5 Occurrence of Lactic Acid Bacteria in Nature 14 

2.6 Saccharomyces cerevisiae 15

CHAPTER THREE

3.0 Materials and Methods 16

3.1 Sample Collection and Sources of Commercial Yeast 16

3.2 Isolation of Yeast from Palm Wine 16

3.3 Characterization of Yeast Isolates 16

3.4 Laboratory Preparation of Burukutu (Fermentation of Sorghum) 16

3.5 Microorganism Used As Starter Culture 17

3.5.1 Preparation and Inoculation 17

3.5.2 Assessment of Fermentation 17 

3.6 Biochemical Analysis 17

3.6.1 pH 17

3.6.2 Total Titratable Acidity (TTA) 17

3.6.3     Temperature                                                                                                               17

3.7 Proximate Analysis 18

3.7.1 Mineral Content Determination 18

3.8 Microbiological Analysis  18

CHAPTER FOUR

4.0 Results 19

CHAPTER FIVE

5.0 Discussion and Conclusion

5.1 Discussion 28

5.2 Conclusion 33

References