CHARACTERIZATION AND STARTER CULTURE POTENTIALS OF LACTIC ACID BACTERIA ASSOCIATED WITH THE FERMENTATION OF COMBINED GRAINS SORGHUM BICOLOR AND PENNISETUM GLAUCUM USED FOR KUNU ZAKI PRODUCTION

ABSTRACT

The study aimed at the Characterization and starter culture potentials of lactic acid bacteria during the fermentation of Sorghum biocolor and pennisetum glaucum for kunu-zaki, to determine the physicochemical properties of kunu-zaki, to enumerate microorganisms associated with kunu-zaki and isolate and characterize lactic acid bacteria from kunu zaki and to determine physiochemical properties of kunu-zaki and to isolate other microorganisms associated with kunu-zaki production. The media used was De Man Rogosa and Sharpe (MRS) Agar in culturing lactic acid bacteria, manufacturer description 67.1g into 1000ml of distilled water. Nutrient Agar in culturing bacteria, manufacturer description 28g into 1000ml of distilled water, MacConkey Agar in culturing coliform, manufacturer description 47g into 1000ml of distilled water, malt extract Agar in culturing yeast, manufacturer description 50g into 1000ml of distilled water (de Man 1960). Starter cultures are added to the raw materials in large numbers and incubated under optimal conditions. In common controlled-fermented products such as Sauer kraut and yoghurt. Lactic acid is produced by the starter culture bacteria to prevent the growth of undesirable microorganisms in non-sterile raw materials and these culture bacteria helps to make the products shelf-stable. These starter culture bacteria derived in the course of these study were Lactobacillus casei, Lactobacillus brevis, Lactobacillus fermentum, Lactobacillus plantarum etc. They help in the fermentation process of kunu-zaki.

TABLE OF CONTENTS

Title page                                                                                                                    i

Certification                                                                                                                ii

Dedication                                                                                                                   iii

Acknowledgments                                                                                                      iv

Table of contents                                                                                                        v

List of tables                                                                                                               vi

List of figures                                                                                                             vii

Abstract                                                                                                                       viii

CHAPTER ONE:

1.1       Introduction                                                                                                    1

1.2       Aim and Objective of the Study                                                                     2

1.2.1 Aim                                                                                                                    2

1.2.2 Objectives                                                                                                          3

CHAPTER TWO:    LITERATURE REVIEW

2.1       Fermentation of Cereal based Foods                                                              4

2.2. Some beneficial attributes of African fermented cereal-based foods                        9

2.2.1. Shelf-life extension and improved nutritional and sensory properties                        10

2.2.2. Inhibition of pathogenic microorganisms in fermented foods.                         10

2.2.3. Production of bacteriocins by lactic acid bacteria                                           12

2.2.4.   Toxic, antinutritional and indigestible compounds incereal foods                        13

CHAPTER THREE

3.1 Sample Collection                                                                                                18

3.2       Glasswares and Media Used                                                                           18

3.3 Determination of Ph                                                                                             19

3.4 Microbiological analysis                                                                                      19

3.4.1 Enumeration of total bacteria                                                                            19

3.4.2 Enumeration of total coliform                                                                           20

3.4.3 Enumeration of Yeasts                                                                                      20

3.4.4    Enumeration of lactic acid bacteria                                                                20

3.4.5    Isolation of Lactic Acid Bacteria                                                                    21

3.4.6 Characterization of lactic acid bacteria                                                             21

3.4.6.1 Morphological characterization                                                                     21

3.4.6.2 Biochemical Characterization                                                                        22

3.4.6.3 Physiological characterization                                                                       23

3.4.7 Identification of lactic acid bacteria                                                                  24

3.5       Safety Properties of LAB                                                                               24

3.5.1    Haemolysis Test                                                                                             24

3.5.2    Antibiotic Resistance Pattern                                                                         25

3.6       Rate of Acid Production                                                                                 25

CHAPTER 4

4.1       RESULT                                                                                                        26

CHAPTER 5

5.1       Discussion                                                                                                       33

5.2       Conclusion                                                                                                      35

5.3       Recommendation                                                                                            35

REFERENCES                                                                                                         36

LIST OF TABLES

Tables                                                                                                 pages

1: pH and Microbial Counts of Kunun-zaki                                       27

2: Morphological Characteristics of Lactic Acid Bacteria Isolated from Kunu-zaki                   28

3: Biochemical and Physiological Characteristics Lactic Acid bacteria Isolated from Kunu-zaki                                             29

4: Haemolytic test of lactic acid bacteria isolated from Kunu-zaki   30

5: Antibiotic Resistance Pattern of Lactic acid bacteria isolated from Kunu-zaki                   31

LIST OF FIGURES

Figure                                                                                         page

1:         Acidification rate by lactic acid bacteria isolated from kunu-zaki                        32

CHAPTER ONE

1.1                                                        INTRODUCTION

In rural and informal settlements of Africa, where electricity and sanitary facilities are not available, fermented sorghum and maize are frequently used as weaning foods because they are inexpensive, can be stored for long periods at ambient temperature and do not require re-heating  before consumption (Wood, 1992).During fermentation, raw materials are converted to food products (by bacteria, yeasts and molds). In a natural fermentation, the conditions are set such that the desired microorganisms grow preferentially and produce metabolic by-products, which give the unique characteristics of the food. In many cases, fermentation contributes to the digestibility and nutritional value of the final product (Towo, 2006). When the yield is unstable and where the desired microorganisms might not grow, or where pathogenic microorganisms might also grow, a controlled fermentation is used. In a controlled fermentation, the fermentative microorganisms are isolated, characterized and then maintained for further use and termed a starter culture. Starter cultures are added to the raw materials in large numbers and incubated under optimal conditions.

In common controlled-fermented products such as sauerkraut and yoghurt, lactic acid is produced by the starter culture bacteria to prevent the growth of undesirable microorganisms in the non-sterile raw materials and these culture bacteria helps to make the products shelf-stable (Onyango et al., 2004).

The consumption of fermented foods has increased greatly since 1970. This includes common foods like yoghurt, buttermilk and fermented sausages as well as ethnic foods such as “Kefir”,

“Kumiss”, “Togwa”, “Tofu”, “Ogi”, “Mageu”, “Kenkey” and others (Board et al., 1995). One of the reasons for the increase in the consumption of fermented foods is because consumers consider these foods to be healthy and natural. The consumption of live cells of desirable microorganisms and their metabolic products in fermented foods does not cause panic or distress in the safety-concerned consumers. These foods have been around for thousands of years and therefore have withstood the test of time (Onyango et al., 2004).

Fermentation is an effective method of food preservation. The process of fermentation by lactic acid bacteria (LAB) is capable of lowering the pH to below 4 in food products. Traditional fermented food, especially maize, sorghum and dairy products represent an important part of the diet of peri-urban and rural communities in South Africa and other developing countries. The use of these products manufactured with non-defined cultures or by back slopping practices is however, steadily declining due to improvement in socio-economic status of people in the society that is taking place (Beukes et al., 2001). These beneficial microorganisms, especially the LAB are selected from the natural biodiversity of microorganisms and represent a unique genetic

resource for food technology and biotechnology for future development in the region (Beukes et

al., 2001).

1.2       Aim and Objective of the Study

1.2.1 Aim

The aim of this study is to evaluate the starter culture potentials of lactic acid bacteria isolated from Kunu zaki.

1.2.2 Objectives

The objective are:

1.     To determine the physicochemical properties of kunu zaki

2.     To enumerate microorganisms associated with kunu zaki

3.     To isolate and characterize lactic acid bacteria from kunu zaki

4.     To determine the starter culture potentials of selected LAB isolates

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