ABSTRACT
Lactic acid bacteria (LAB) have been used for the fermentation of food and feed products since ancient days and today their major applications are still in the food industry as starter cultures, where they have been known to improve the nutritional quality of the foods. This study was aimed at determining the contribution of Lactic Acid Bacteria to improve the nutritive value of fermented Pentaclethra macrophylla enriched with Brewer’s yeast. Four LAB species were isolated from Pentaclethra macrophylla of which were Lactobacillus fermentum, Streptococcus lactis, Lactobacillus plantarum, and Leuconostoc mesenteroides based on morphological, biochemical and physiological characteristics. Leuconostoc mesenteroides was the most abundant LAB observed in this study with 43.75% occurrence in the studied samples while Lactobacillus fermentum was the least abundant with 12.5%. The study showed the ability of LAB and Brewer’s yeast to contribute to the fermentation of Pentaclethra macrophylla seeds. This was carried out using the colorimetric method of vitamin determination by Madhavi and Jyothi., (2016). The result showed the concentration of vitamin B2 in unfermented Pentaclethra macrophylla seeds to be 0.0292mg/ml. The concentration of vitamin B2 in fermented Pentaclethra macrophylla seeds (Ugba) with LAB starter culture was 0.0489mg/ml while the concentration of vitamin B2 in Ugba fermented with only Brewer’s yeast was 0.0275mg/ml and that fermented with both LAB and Brewer’s yeast was 0.0522mg/ml. The ability of the LAB isolates and Brewer’s yeast to produce riboflavin can serve as a method of enriching ugba and also fortifying other fermented foods. Hence, using LAB and Brewer’s yeast combined as a starter will be a preferred option than the traditional starters.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgments iv
Table of contents v
List of tables vii
Abstract viii
CHAPTER ONE
INTRODUCTION 1
1.1 Aim
and Objectives of the Study 5
1.1.1 Aim 5
1.1.2 Objectives 5
CHAPTER TWO
LITERATURE REVIEW 6
2.1 Fermentation 6
2.1.1 Importance of fermentation 8
2.2 Fermented Foods 10
2.2.1 Ugba and its importance 12
2.3 Lactic acid bacteria 18
2.3.1 African Oil Bean Tree (Pentaclethra macrophylla) 19
2.3.2 Importance of African Oil Bean Tree (Pentaclethra macrophylla) 22
2.4 African Oil Bean Seed 24
2.4.1 Chemical Composition of the Seed 24
CHAPTER THREE
MATERIALS AND METHODS 26
3.1 Source of
Raw Material 26
3.2 Materials 26
3.3
Preparation of Ugba 27
3.4 Preparation
of Homogenate Ugba Samples 27
3.5 Inoculation
of Samples 27
3.6 Colony
Count of Isolates 27
3.7 Characterization
and Identification of Isolates 28
3.8 Isolation
of Lactic Acid Bacteria 28
3.8.1 Phenotypic Characterization 28
3.8.2 Biochemical Characterization 29
3.8.2.1 Gram
Staining 29
3.8.2.2 Catalase
Test 29
3.8.2.3 Spore Stain Test 30
3.8.2.4 Citrate Test 31
3.8.2.5 Carbohydrate Fermentation Test 31
3.8.2.6 Exopolysaccharide production 32
3.8.3 Physiological Characterization of Lactic
Acid Bacteria 32
3.8.3.1 Growth at Different Temperatures 32
3.8.3.2 Salt Tolerance Test 32
3.8.3.3 Growth at Different pH 32
3.9 In Vitro/ Laboratory Fermentation of Ugba Using Lab Isolates for
Vitamin 33
Production
3.10 Colorimetric Analysis for Determination of
Vitamin B2 33
CHAPTER FOUR
RESULTS 33
CHAPTER FIVE
DISCUSSION, CONCLUSION AND RECOMMENDATION 39
5.1 Discussion 39
5.2 Conclusion
and Recommendation 42
References 44
Appendix I 51
LIST
OF TABLES
|
TABLE
|
TITLE
|
PAGE
|
|
2.1
|
Traditionally Fermented
Foods in Nigeria
|
11
|
|
2.2
|
Uses
of Pentaclethra macrophylla Benth
in West African.
|
18
|
|
4.1
|
Morphological,
Biochemical and Physiological Characteristics of Lactic Acid Bacteria
Isolated from Pentaclethra macrophylla
|
36
|
|
4.2
|
Carbohydrate
Fermentation Profile of Lactic Acid Bacteria Isolated from Pentaclethra macrophylla
|
37
|
|
4.3
|
Occurrence of LAB
Isolates in Fermented Pentaclethra
macrophylla
|
38
|
|
4.4
|
Vitamin B2 (Riboflavin) Content
in Unfermented Pentaclethra macrophylla
and fermented Pentaclethra macrophylla with different
starter cultures
|
38
|
CHAPTER ONE
INTRODUCTION
In
Africa many species of trees serve as sources of food and for medicinal
purposes to indigenous people.The African oil bean (Pentaclethra macrophylla Benth) is a leguminous woody plant
(subfamily: Mimosoideae) that occurs naturally in the humid lowlands of West
tropical Africa Endemic to relatively acid soils, the species holds promise of
a good alley farming crop because of its soil improvement properties.The
African oil bean is planted mainly because of its edible seed which has been
found to be highly nutritious with adequate amounts of proteins and calories
that meet the recommended daily allowances. The seed is usually consumed via
fermentation to ‘ugba’ a highly nutritious condiment and snack food. It could
also be consumed via roasting, as an alternative to fermentation. Both the
fermented and roasted products are found to retain the seed nutrients and
improve on their digestibility.(Victor et
al.,2003)
Pentaclethra macrophylla
(African oil bean) produces its seeds used for ugba production from a perennial
legume tree. The trees are often planted along the sides of roads as shade
trees and around communities as cash crops. African oil bean is a tropical tree
crop found mostly in the Southern rain forest zone of West Africa and has been
cultivated since 1937. It belongs to the leguminosae family and sub-family
Mimosoideae. African oil bean tree grows to about 21 meters in height and to
about six meters in girth and it is well branched, forming crown-like canopy.
The leaves have stout angular petiole. The compound leaves are usually about 20
centimeters large and covered with rusty hairs. The flowers are creamy,
yellowish or pinkish-white and sweet smelling. The main flowering season is
between March-April after which the pods (brown and woody when matured) open by
explosive mechanism, dispersing the seeds and curls up, releasing about eight
flat, glossy brown seeds measuring about 5-7 cm in diameter and weighing between
15-20g.
In
Nigeria, it thrives in the eastern and western parts. Ugba is the Igbo name for
the fermented African oil bean seeds. It is called Apara by the Yoruba’s and
Ukana by the Efiks. Ugba, a product of alkaline fermentation of oil bean seeds
(Pentaclethra macrophylla) is very
popular among the Ibos and other ethnic groups in southern Nigeria. The African
oil bean seed is fermented and consumed especially in eastern states of
Nigeria. The fermented product Ugba (old Imo State) or Ukpaka (Old Anambra
State) is eaten alone or with other ingredients like stockfish, garden egg,
sliced tapioca or can be mixed with vegetable popularly known as Africa salad
in the Eastern part of Nigeria . The oil bean seeds contain 8-10% carbohydrate
and 4748% of fatty acid. About 75% of the total oil in the seed is made up of
unsaturated fatty acids, predominantly oleic and linoleic acid. The
pharmacological importance derivable from its seeds, roots, bark and leaves are
of benefit in the treatment and management of obesity, itching, heart problems,
high blood pressure(Ajugwo et al.,2013)
Lactic acid bacteria (LAB) are a group of related
bacteria that produce lactic acid as a result of carbohydrate fermentation.
They comprise a clade of Gram positive, usually non motile acid tolerant
microorganisms. They are generally non-spore forming, non-respiring cocci,
coccobacilli or rods. LAB growth lowers both the carbohydrate content of the
food that they ferment and the pH due to the lactic acid production. Certain LAB
strains have been reported to be highly antagonistic to biofilm forming S.aureus (Ammor et al., 2006). LAB strains
are potentially promising because they generate bactericidal bioactive peptides
(bacteriocins) and enzymes that are able to control biofilm formation and
growth of pathogens (Millette et al.,
2006)
Lactic acid bacteria exert strong antagonistic
activity against many microorganisms, including food spoilage organism and
pathogens. Some strains may contribute to food preservation of fermented food
by producing bacteriocins (Brink et al.,
1994). The major parameters involved in bacterial growth inhibition are the pH,
which decreases by the production of organic acid, nutrient competition,
hydrogen peroxide and antibiotic production. S.aureus is a Gram positive
coccus, non-motile non-spore forming facultative anaerobic which appears as
grape like clusters. It is a common pathogen associated with hospital acquired
diseases which causes major problem for public health. One of the major causes
of staphylococcal enterotoxin is vomiting and diarrhea when ingested and is
responsible for staphylococcal food poisoning.(Nostro et al., 2002)
Lactic acid bacteria strains play a key role of
maturation in fermented meat products. Of course, lactic acid bacteria strains
can use as starter cultures have some important characteristic feature but this
feature are not always adequate to make sure the sensory qualities, which are
found in traditional meat product like pastrami or sausage. For this reason,
extension activities are necessary like as lipolytic and proteolytic activity.
Similarly, proteolysis and lipolysis activity contribute to the aroma and
textural properties of pastirma. Traditionally lipolysis was thought to be
related to bacterial lipase activity. Some lactic acid bacterial strains have
the ability to produce various lipolytic enzymes groups and generally these
production in question are extracellular. As a general thing, biochemical and
physicochemical parameters like temperature, pH, and presence of lipids,
inorganic salts, nitrogen and carbon source influence efficiency of lipase
enzymes produced by lactic acid bacteria extensively(Dincer and Kivanc, 2017)
The lipolytic activity of LAB has been more
extensively researched in several areas of food production. Nevertheless,
lipolytic activity of LAB isolated from pastırma has not been investigated up
to now. The present work aims to screening for liypolytic activities of lactic
acid bacteria representing the geniuses Lactobacillus,
Enterococcus, Pediococcus, Leuconostoc
and Weissella isolated from pastırma
and aims to determinate the possibilities of using this strains industrially. (Dincer
and Kivanc, 2017).
1.1 Aim and Objective
1.1.1 Aim
This
work is aimed identifying the contribution of lactic acid bacteria to improve
the nutritive value of fermented Pentaclethra
macrophylla enriched with brewer’s yeast.
1.1.2 Objective
The
objectives of this work are:
1. To
isolate ,characterize and identify the microorganisms present in fermented Pentaclethra macrophylla
2. To
determine the contribution of lactic acid bacteria on fermented Pentraclethra macrophylla
3. To
identify the nutritive value of Pentaclethra
macrophylla enriched with brewer’s yeast
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