ABSTRACT
Ugba is a delicacy popular among the Ibo ethnic group of Nigeria, made by the fermentation of boiled seeds of African oil bean (Pentaclethra macrophyllea Benth). The microorganisms and compounds influencing the organoleptice properties of ugba were studied. The pure cultures of these microorganisms isolated from (ugba) sample produced by traditional method, were used in singles and in combinations to ferment African oil bean shreds. The ugba so fermented were analyzed organoleptically and the sensory scores statistically analyzed using analysis of variance at p < 0.05. Compounds in the samples of oil extracted from unfermented African oil bean shreds and ugba samples fermented for 72 hours with the microorganisms (in singles and in combinations) were analyzed by gas chromatograph. The results showed that the following microorganisms were involved in the fermentation of ugba: Staphylococcus saprophyticus, Bacillus pumilus, Bacillus subtilis, and Bacillus licheniformis. The organoleptic tests showed that the sample fermented by a mixed starter culture of Bacillus subtilis and Bacillus licheniformis was generally liked in all parameters tested, which implied overall best. Compounds found in unfermented and fermented ugba were nineteen in number. Out of this number, eleven were found in the unfermented sample, while eight were in the fermented ugba. The best sample contained the following compounds: ethanol, ethyl stearate, ethyl oleate, ethyl linoleate, ethyl phenol and ethyl octanoate (their percentage concentrations ranged from 2.69% for ethyl octanoate to 67.85% for ethanol). These compounds influenced the perceived ugba flavour but had no direct influence on the colour and texture of ugba samples.
TABLE OF CONTENTS
Title page
Certification
Copyright statement
Dedication
Acknowledgement
Table of contents
List of figures
List of tables
List of appendices
Keyword in context
Abstract
CHAPTER ONE
1.0 Introduction
CHAPTER TWO
2.0 Literature Review
2.1.0 Fermented foods
2.1.1 Classification of fermented foods
2.2 Legume-based fermented foods
2.2.1 Effect of flavour on legume-based fermented foods
2.3 African oil bean seeds
2.4 Production of ugba
2.5 Consumption pattern/uses of ugba
2.6 Preservation and storage of ugba
2.7 Fermenting microorganisms and chemical changes during ugba production
2.7.1 Microorganisms in ugba fermentation
2.7.2 Chemical changes during ugba production
2.8 Proximate composition and nutritive value of African oil bean seed
2.9 Toxicology of African oil bean seeds
CHAPTER THREE
3.0 Materials and methods
3.1 Raw materials procurement
3.2 Sorting/cleaning of the African oil bean seeds
3.3 Proximate analysis of African oil bean seeds
3.3.1 Moisture content determination
3.3.2 Crude fat determination
3.3.3 Crude fibre determination
3.3.4 Crude protein determination
3.3.5 Ash content determination
3.3.6 Carbohydrate content determination
3.3.7 Energy value determination
3.4 Production of ugba (control sample): A fermented African oil bean seed
3.5 Isolation, characterization and identification of microorganisms from fermenting African oil bean shreds
3.5.1 Isolation and identification of microorganisms from fermenting African oil bean shreds
3.6 Preparation of starter cultures from pure bacteria isolates
3.6.1 Preparation of ugba using starter cultures
3.6.2 Storage stability of ugba after 72 hours fermentation
3.7 Determination of pH of unfermented and fermented African oil bean samples
3.8 Determination of compounds in unfermented and 72 hours fermented African oil bean shreds
3.9 Sensory evaluation and statistical analysis of the ugba samples
3.9.1 Sensory evaluation of ugba samples
3.9.2 Statistical analysis
3.9.3 Determination of effect of identified compounds on organoleptic properties of ugba
CHAPTER FOUR
4.0 Results and discussions
4.1 The proximate composition of the African oil bean seeds
4.2 Observations during ugba production
4.2.1 Storage stability of preserved ugba samples
4.3 Microorganisms identified from ugba fermentation
4.4 Concentrations of microorganisms involved in ugba production
4.4.1 Concentrations of microorganisms and their effects on production of ugba (control)
4.4.2 Viable counts of bacterial starter cultures used in experiential ugba production
4.5 Compounds contributed by microorganisms during ugba production
4.5.1 Identified compounds in ugba during 72 hours fermentation of African oil bean shreds
4.5.2 Percentage concentrations of compounds identified during ugba production
4.6 Organoleptic properties of ugba fermented with starter cultures of bacteria isolates
4.7 The pH values and organoloeptic characteristics of ugba samples fermented for 72 hours
4.8 Comparison of compounds and organoleptic properties of ugba samples
4.9 Effect of association of starter organisms on quality characteristics of ugba samples
CHAPTER FIVE
5.0 Conclusions and recommendations
5.1 Conclusions
5.2 Recommendations
References
Appendices
