CONTRIBUTION OF YEAST IN MAIZE FERMENTATION

ABSTRACT

The contribution of yeast in maize fermentation for ogi production was studied. Maize seeds were fermented for 72hrs and sub-samples were collected and analyzed every six hours. Quality characteristics of the fermenting liquor was determined including microbial load and flora. Obtained results shows that the bacterial load was in the range from 1.13×106 cfu/ml to 2.05×106 cfu/ml while the fungal load ranged from 2.3×103 cfu/ml to a maximum of 5.41×103 cfu/ml. The bacterial load reduced to 1.59×106 cfu/ml while the fungal load reduced to 2.1×103 cfu/ml. Bacterial flora of the fermenting liquor consisted of Lactobacillus sp, Staphylococcus sp, Streptococcus sp, Bacillus sp, Pseudomonas sp, while the fungal load consisted of Yeasts sp, Aspergillus sp, Fusarium sp, and Rhizopus sp. The contribution of yeast was assessed by test on the ability to produce enzymes. Obtained results also show that the yeast isolates demonstrated enzyme acttivties in the form of amylase, lipase, and protease activity. Amylase activity was in the range of 3.3 enzyme units to 20.81 enzyme units from the first day to the third day. Lipase activity was in the range of 1.43 to 2.87 enzyme units of the same period while protease activity was in the range of 6.20 to 7.53 enzyme units of the same period. It was concluded that major contribution of yeast in the fermentation, lies with the enzymatic hydrolysis of the carbohydrate during the fermentation with the accompanied by-products including organic acids, alcohol etc.

TABLE OF CONTENTS

Tile page

Certification

Dedication

Acknowledgement

Table of contents

List of Tables

List of Bar Charts

Abstract

CHAPTER ONE

 1.0 Introduction

1.1 Background of Study

1.2 Aims and Objectives

CHAPTER TWO

2.0 Literature Review

2.1 Yeast

2.2 Fermented Maize

2.3 Yeast and Indigenous Fermented Foods

2.4 Prospect of Yeast in Fermented Foods

CHAPTER THREE

3.0 Materials and Methods

3.1 Sample collection

3.2 Sample and Media Preparation

3.2.1 Sample Preparation

3.2.2 Media Preparation

3.3 Fermentation of Maize

3.4 Determination of Microbial Load of Fermenting Maize Liquor

3.5 Isolation and identification of Microbes

3.6 Characterization of Isolates

3.6.1 Characterization of Fungi Isolates

3.6.1.1 Colony features

3.6.1.2 Structural features

3.6.2 Characterization of Bacteria Isolation

3.6.2.1 Colony features

3.6.2.2 Structural features

3.6.2.3 Biochemical Tests

3.6.2.4 Sugar Utilization Test

3.7   Identification of Isolates

3.8   Evaluation of Yeast Contribution

CHAPTER FOUR

4.0 Results and Discussion

4.1  Results

4.2 Discussion

CHAPTER FIVE

5.0 Conclusion and Recommendation

5.1 Conclusion

5.2 Recommendation

References

Appendix

 LIST OF TABLES

4.1 Microbial Load of Fermenting Liquor

4.2 Bacterial Isolates from 72hr Fermenting Maize Liquor

4.3 Fungal Isolates from 72hr Fermenting Maize Liquor

4.4 Enzyme activity of Fermenting Maize Liquor

LIST OF BAR CHART

Bacterial Load Bar Chart                                                                                                  22

Fungal Load Bar  Chart                                                                                                    23                              

CHAPTER ONE

INTRODUCTION

1.1 BACKGROUND OF THE STUDY

 Yeasts are microorganisms of great importance and economic interest due to their application in both traditional and modern biotechnology (Orbera, 2004). Lanchance et al., (1998) and Yarrow, (1998) reported yeasts to be one of the most employed biocatalyst in biotechnology being the common microorganisms associated with fermented foods. Also, yeasts have been used as probiotics in humans for many years because they exert some influence on the intestinal flora (Czerucka et al., 2007, Kumura et al., 2004). Some available research reports (Adams, 1999, Nout, 2001, Hansen, 2002) show that cultures and species of yeasts involved in fermented foods, do not pose health risk and as such are generally recognized and designated as GRAS- Generally Recognised As Safe-organisms.

The contribution of yeasts (and other microorganisms) in food fermentation vary with the type of food, environment, species of organisms, length of fermentation etc. Due to the fact that some of the organisms (including yeasts) associated with food fermentation, have long history of safe use in foods, they are sometimes implemented as protective cultures (probiotics) to antagonize the growth of some spoilage and pathogenic microorganisms in foods (Chiang, et al., 2000). According to Greppi et al., (2013), the roles of yeast in fermented indigenous foods and the dynamics of the yeasts, are poorly studied. However, possible roles of yeasts, in fermented foods  has been listed (Jespersen, 2003). Romano et al., (1997) reported contribution of yeasts in organoleptic properties of fermented food products while Haefner, et al., (2005) and Hjortmo, et al.,(2005) reported their upgrading of nutritional value of fermented foods. Similarly the roles of yeasts with probiotics effects, their contribution to human health and detoxification of mycotoxins has also been reported (Mumy, et al., 2008, Pesbersen, et al., 2012, Shetty,  2007).

“Akamu” also called “Ogi” is a product of fermentated maize and is widely consumed in the length and breath of Africa (Amaokoromo, 2011). The product of fermentation of maize

(Akamu) is sold in different forms including as wet cakes which could be reconstituted into a porridge called “pap”. Many different species of microorganisms have been implied in the fermentation of maize to produce ogi.  Mbalarem-Aniebo and Udemgba, (2012), isolated many different bacteria species including Staphylococcus, Lactobacillus, Corynebacteria, Enterobacter, Bacillus, Micrococcus, as well as fungi of the species of Aspergillus, Fusarium, Rhizopus, and yeasts of Saccharomyces species.

Since yeast occur in a wide range of fermented foods of plant and animal ingredients (Kofi, et al., 2005) and fermented foods are essential components of diets in many developing countries (Sourabh,  2011), an understanding of yeasts in the fermentation of indigenous food is desirable for full appreciation and implementation in domestic as well as individual food productive techniques. Against this background, this project work seeks to study the contribution of yeasts in the fermentation of maize to produce Akamu.

1.2 AIMS AND OBJECTIVES

The objective of this project work is generally to study the contribution of yeasts in the fermentation of maize to produce Akamu-an indigenous common breakfast food. The objectives includes specifically the following:

i. Determination of microbial load of the fermenting maize liquor at quarter hourly intervals.

ii. Isolation, characterization and identification of yeasts flora in the fermenting liquor.

iii. To evaluate the contribution of yeasts during the fermentation period with regards to enzyme activity, substrate degradation and or modification.

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