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
- Background of the study 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.
