MICROBIAL PROFILE OF FERMENTING DAWA DAWA (AFRICAN LOCUST BEANS)

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Dawa dawa is known as a nutritious rich condiment all over Nigeria. is utilized as delicacy, used as food seasoning, flavour enhancer and aroma. In this study three samples of fresh African locust bean were subjected to 5 days of fermentation. The mean heterotrophic bacterial counts during the 5 days of fermentation ranged from 1.3 x 101 CFU/g at the start of fermentation to 7.66 x 1010CFU/g on the 5th day of fermentation, fungal counts ranged from 1x 102 CFU/gat the start of fermentation to 9.1 x 104 CFU/g on the 5th day of fermentation. Mean fungal counts ranged from 1x 102 CFU/gat the start of fermentation to 9.1 x 104 CFU/g on the 5th day of fermentation. 15 bacterial isolates were identified to include: Lactabacillus plantarium 4(26.67%), Bacillus cereus 2(13.33%), Bacillus subtilis 1(6.67%), Enterobacter sp. 2(13.33%), Leuconostoc sp. 3(20%) and Micrococcus luteus 1(6.67%). 9 fungal isolates were identified to include: Aspergillus fumugatus 3(33.33%), Penicillium sp. 3(33.33%), Rhizopus sp. 1(11.11%) and Aspergillus niger 2(22.22%). The presence of Bacillus ceases after 3 days (72 hours) of fermentation. Lactobacillus sp. and Leuconostoc were more persistent in occurrence as the both appeared in day 2,3 and 4. This study also reveals the fermentation of dawa dawa to be an alkaline process as pH ranged from 5.82 at 0 hour to 9.57 at 120 hours. Correlational analysis using Microsoft EXCEL 2007 revealed a positive correlation between pH of dawa dawa and its bacterial loads, pH and fungal loads, time of fermentation and pH. However, there was a negative correlation between pH and Titratable acidity. Bacillus cereus which can produce enterotoxins that can cause flatulence and diarrhea if consumed can be hazardous. Extension of the fermentation time could lead to the succession of more pathogenic microorganisms in unhealthy numbers to the detriment of potential consumers.

TABLE OF CONTENTS

TITLE PAGE                                                                                                    i

CERTIFICATION                                                                                           ii

DEDICATION                                                                                                iii

ACKNOWLEDGEMENTS                                                                            iv

ABSTRACT                                                                      v

TABLE OF CONTENTS                                                                                vi

LIST OF TABLES                                                                                          vii

LIST OF FIGURES                                                                                        viii

CHAPTER ONE: INTRODUCTION

  1. Background of the study                                                                         1
    1. Objectives of the study                                                                            1

CHAPTER TWO: LITERATURE REVIEW

2.1    Nutritional composition of African locust bean                                                3

2.2    Preparation of dawa dawa condiment                                                   6

2.2.1 Depulping                                                                                              7

2.2.2 Boiling                                                                                                   8

2.2.3 Steaming                                                                                                8

2.2.4 Dehulling                                                                                               8

2.2.5 Separation                                                                                              9

2.2.6 Fermentation                                                                                          9

2.3 Bacteria associated with fermentation of African locust bean                 12

2.4 Fungi associated with fermentation of dawa dawa                                  13

CHAPTER THREE: MATERIALS AND METHODS

3.1    Materials                                                                                                15

3.1.1 Glassware                                                                                               15

3.1.2 Equipment                                                                                              15

3.1.3 Media and reagents                                                                                16

3.2    Sample collection and processing                                                          16

3.3    Determination of the pH and Titratable acidity of dawa dawa                        17

3.4    Isolation of dawa dawa fermenting fungi                                 18

3.5    Identification of dawa dawa fermenting fungi                                     18

3.5.1 Gram staining                                                                                         19

3.5.2 Motility test                                                                                           20

3.5.3 Catalase test                                                                                           21

3.5.4 Methyl red-voges proskaeur test (MR-Vp)                                            22

3.5.5 Sugar fermentation test                                                                          23

3.5.6 Indole test                                                                                              24

3.5.7 Citrate test                                                                                             25

3.5.8 Urease test                                                                                             25

3.5.9 Oxidase test                                                                                           26

CHAPTER FOUR: RESULTS

4.1    Bacterial and Fungal count during the process of dawa dawa fermentation   27

4.2    Organoleptic changes and frequency of isolates during the

         fermentation of dawa dawa                                                                   28

4.3    Correlation and scatter plot of physicochemical parameters                 31

CHAPTER FIVE: DISCUSSION AND CONCLUSION

5.1    Discussion                                                                                              35

5.2    Conclusion                                                                                             37

REFERENCES                                                                                              38

LIST OF TABLES

TABLE 1: Proximate composition of raw African locust bean and Dawadawa               5

TABLE 2  Mean bacterial and fungal count, pH and titratable acidity of fermenting dawadawa                                                                            27

TABLE 3: Organoleptic changes of dawa dawa samples observed

during fermentation                                                                            29

TABLE 4: Percentage frequency of bacterial isolates                                   

TABLE 5: Percentage frequency of fungal isolates                                       30

LIST OF FIGURES

FIGURE 1: Scatter plot and correlation of pH of dawa dawa and Log10 of bacterial count (CFU/g)

FIGURE 2: Scatter plot and correlation of pH of dawadawa and Log10 of fungal count (CFU/g)

FIGURE 3: Scatter plot and correlation of pH dawadawa and fermentation time

FIGURE 4: Scatter plot and correlation of pH dawadawa and its Titratable acidity

CHAPTER ONE

INTRODUCTION

1.1 Background of the study

Locust beans condiment (iru- Yoruba, Daddawa- Hausa, Ogiri- igbo), is utilized as delicacy, used as food seasoning, lanet enhancer and aroma. It is produced locally and can be purchased in local.markets all over Nigeria (Adeoye et al., 2018). African locust bean with botanical name Parkia bigblobosa is a leguminous plant found in the savanna region of Nigeria. It’s botanical name was given to it by Robert Brown, a Scottish botanist in 1826 (Abdoulaye, 2012). Parkia bigblobosa seeds is known as Iyere in Yoruba land while the fermented seed is called “iru” (Ojewumi et al., 2018). Iru or dawadawa is also consumed in.many different countries having different names such as dawadawa in Nigeria and Ghana. Afintin and Sonru in Benin Republic, not to in Senegal and Soumbala in Burkinafaso. Furthermore, it is called natto in Japan and Kinema in Nepal (Ojewumi et al., 2018). Fermentation is the biological conversion of complex substrate such as starch or sugar into simple compounds by microorganisms (Ojewumi et al., 2018). It can also be defined as the production of energy from food without using oxygen.