ABSTRACT
The de-bittering process is traditionally applied to Bitter leaves (Vernonia amygdalina) to enhance palatability. Effects of de-bittering process on the nutrient composition, carotenoid content and profile of Vernonia amygdalina was evaluated in this research work. V. amygdalina leaves were treated by washing with water, salt water, boiling and sundrying. The fresh leaves contained the highest quantities of Beta-carotene, phytochemical, vitamins and minerals. Washing with water and salt depleted the Total Beta-carotene contents of the leaves from (169.51 to 9.15)µg. Boiling with water actually increased the Total Beta-carotene contents from (169.51 to 178.05)µg. All the treatments except de-bittering with water only significantly reduced the Total Beta-carotene contents (169.51 to 24.89)µg but the most drastic was de-bittering using salt water (169.51 to 9.15)µg. The water soluble vitamins were reduced more by the boiling of the leaves in water: B9 (0.96 to 0.57)mg, B12 (0.35 to 0.22)mg and Vit C (40.31 to 26.13)mg. The mineral content were also significantly reduced by boiling: Fe (3.62 to 1.07)mg, Zn (2.55 to 1.78)mg, Cu (1.27 to 0.72)mg and Mg (69.33 to 58.84)mg. V. amygdalina samples were found to be a very good source of iodine (50.50mg/100g) and de-bittering with water did not reduce the iodine content significantly. Phytochemicals were least reduced by the sundrying process (29% for Tannins, 14% for flavonoid, 16% for saponins and 19% for phenols. De-bittering of V. amygdalina to improve its palatability leads to the loss of nutrients, while boiling in water improves the beta carotene content, it leads to loss of water soluble vitamins.
TABLE OF CONTENTS
Contents
Pages
Cover page
Title page i
Certification ii
Declaration iii
Dedication iv
Acknowledgment v
Table of content vi
List of tables ix
List of figures x
List of plates xi
Abstract xii
CHAPTER 1: INTRODUCTION
1.1 Background of study 1
1.2 Statement of the problem 2
1.3 Justification 2
1.4 Objective 3
CHAPTER 2: LITERATURE REVIEW
2.1 Vernonia amygdalina as a
green leafy vegetable 4
2.1.2 Food uses of Vernonia
amygdalina for man 4
2.1.3 Food uses of V. amygdalina for animal feed 5
2.2 Medicinal uses of Vernonia
amygdalina 5
2.2.1 Antibacterial properties 6
2.2.2 Antiparasitic activity 6
2.2.3 Antimalarial/antiplasmodial activity 7
2.2.4 Anticancer and cytotoxic effect 7
2.2.5 Liver protection 9
2.2.6 Antidiabetic effect 9
2.2.7 Hypolipidemic effect 11
2.3 Biological activities of nutrient and phytochemicals found in Vernonia amygdalina 11
2.3.1 Beta-carotene (BC) 11
2.3.2 Tannins 12
2.3.3 Flavonoid 13
2.3.4 Phenol 13
2.3.5 Saponin 13
2.4 Mineral 14
2.4.1 Copper (Cu) 14
2.4.2 Iron (Fe) 15
2.4.3 Magnesium (Mg) 16
2.4.4 Zinc (Zn) 17
2.4.5 Iodine (I) 17
2.5 Vitamins 18
2.5.1 Pro Vitamin A 18
2.5.2 Vitamin B9 19
2.5.3 Vitamin B12 19
2.5.4 Vitamin C 20
CHAPTER 3: MATERIALS AND METHODS
3.1 Source of Material 22
3.2 Sample Preparation 22
3.3 Determination of Nutrient and Phytochemicals 29
3.3.1 Determination of Beta-carotene 29
3.3.2 Determination of Tannins 31
3.3.3 Determination of Phenol 31
3.3.4 Determination of Flavonoid 32
3.3.5 Determination of Saponin 32
3.4 Determination of Minerals 33
3.4.1 Determination of Iron 33
3.4.2 Determination of Magnesium 33
3.4.3 Determination of Zinc 33
3.4.4 Determination of Copper 34
3.4.5 Determination of Iodine 34
3.5 Determination of Vitamins 35
3.5.1 Determination of Vitamin A 35
3.5.2 Determination of Vitamin B9 36
3.5.3 Determination of Vitamin B12 (Cyanocobalamin) 36
3.5.4 Determination of Vitamin C 36
3.6 Statistical Analysis 37
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Effects of different processing treatments on the nutrients
composition of Vernonia amygdalina leaves 38
4.1.1 Pro-vitamin A content 38
4.1.2 Folate (Vitamin B9) content 38
4.1.3 Vitamin B12 content 39
4.1.4 Vitamin C 39
4.2.1 Iron (Fe) content 41
4.2.2 Zinc (Zn) content 41
4.2.3 Copper (Cu) content 42
4.2.4 Magnesium (Mg) content 43
4.2.5 Iodine (I) content 43
4.3 Effect of different processing treatments on the phytochemical content of Vernonia
amygdalina leaves 45
4.4
Effect of different processing treatments on the Total Beta-carotene content of
Vernonia amygdalina leaves 48
4.5 Carotenoid profile of Vernonia
amygdalina leaves given different de-bittering treatments 51
CHAPTER 5: CONCLUSION 57
References 58
Appendix 76
LIST
OF TABLES
Tables
Pages
3.1
Treatments given to Vernonia amygdalina samples
28
4.1
Effect of de-bittering treatments on the vitamin content of
Vernonia
amygdalina leaves 40
4.2
Mineral content of Fresh and processed Vernonia amygdalina
leaves
44
LIST
OF FIGURES
Figures Pages
4.1
Phytochemical content of fresh
and processed Vernonia amygdalina
leaves 47
4.2 Total
beta-carotene
content of fresh and
processed Vernonia
amygdalina leaves 50
4.3 Carotenoid profile of fresh Vernonia amygdalina leaves 52
4.4. Carotenoid
profile of V. amygdalina leaves
de-bittered by squeeze-washing
with water 53
4.5 Carotenoid
profile of V. amygdalina leaves
de-bittered by squeeze-washing
with water and salt 54
4.6 Carotenoid
profile of boiled V. amygdalina leaves 55
Figure 4.7
Carotenoid profile of V. amygdalina leaves reduced in size and
sundried 56
LIST
OF PLATES
Plates
Pages
3.1 Sample 1: Fresh Bitter leaves 23
3.2 Sample 2: De-bittered by squeezing-washing of fresh bitter leaves in
water 24
3.3 Sample 3: De-bittered by squeezing-washing of fresh bitter leaves in
water
and salt. 25
3.4 Sample 4: De-bittered by boiling of fresh bitter leaves in water 26
3.5 Sample 5: Fresh bitter leaves reduced in size and sundried 27
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND
OF STUDY
Bitter leaf (Vernonia amygdalina)
is a shrub that grows upto 10m tall with leaves of about 6mm in diameter and
elliptic in shape. It grows throughout tropical Africa and has been
domesticated in various parts of West Africa including Nigeria, where it is
locally used as vegetable in soups (Etim et
al., 2012; Habtamu and Melaku, 2018). It is known as "bitter
leaf" in English (Okokon and Onah 2004), "Grawa" in Amharic,
"Ewuro" in Yoruba,"Etidot" in Ibibio, "Onugbu" in
Igbo, "Ityuna" in Tiv, "Oriwo" in Edo and
"Chusar-doki" or "Shuwaka" in Hausa (Egedigwe, 2010).
V. amygdalina
is found commonly in tropical West Africa and had a lot of bitter principles in
every part of the plant which is due to anti-nutritional factors like
alkaloids, saponins, tannins and glycosides (Bonsi et al., 1995).
V. amygdalina has been reported to
demonstrate antihelmitic
and antimalarial
properties (Abosi and Raseroka, 2003), antidiabetic and antihypertensive
properties (Oboh, 2003), antitumorigenic properties (Izevbigie et al., 2004), analgesic and antipyretic
activities (Tijjani et al., 2017),
hypoglycemic and hypolipidaemic effects in experimental animals (Nwanjo, 2005).
The presence of
alkaloids, steroids, glycosides, flavonoids, tannins, saponins, phlobatannins,
and phenolics in the extracts of V.
amygdalina are responsible for its antimicrobial actions (Taleb-contini et al., 2003; Mandalari et al., 2007; Nenaah, 2013; Jasim et al., 2015; Al-Harbi et al., 2017; Jin et al.,2017).
In some African
countries including Nigeria, this plant species is traditionally used to treat
many ailments including diabetes (Akah and Okafor, 1992), malaria, helminth
infections, fever (Magadula and Erasto, 2009), promote wound healing (Adetutu et al., 2011) and to treat microbial
infections (Noumedem et al., 2013).
Also, the Hausa tribe of the northern part of Nigeria used the root and twig of
V. amygdalina to treat stomach-ache
and gastrointestinal troubles (Akinpelu, 1999). It is also prescribed to
nursing mothers as it improves lactation (Anibijuwon et al., 2012).
They are also
used as local medicine or herb against parasites. The plant is well known for
its antidiabetic and antihypertensive properties, and also used in the
treatment of headache and fever (Oboh, 2003).
The leaves of bitter leaf are very bitter because of the presence of
antinutritional components such as alkaloids, saponins, glycosides and tannins.
The leaves are therefore treated by washing and cooking before eating as soup
and medicine (Oboh, 2005).
1.2
STATEMENT OF THE PROBLEM
Bitter leaf is a plant product with good potentials for promoting good
health when used as foods.
Bitter leaf has a characteristics odour and a bitter taste which is not
palatable to consumers. De-bittering is a process in which the unique bitter
juice and anti-nutritional components in leafy vegetables are removed to
enhance palatability. There are various primitive and innovative methods of
de-bittering utilized by various ethnic groups/people. The interest of this
work is to study the effect of different de-bittering/processing methods on the
beta carotene, phytochemicals, vitamins and minerals content of bitter leaf and determine the
processing method that leads to better retention of nutrients especially the
antioxidants (Beta Carotene, Vitamin A, and Vitamin C) and blood building micronutrients.
1.3
JUSTIFICATION
The bitter taste of V. amygdalina hinders people from consuming
it despite its perception as a medicinal and nutritive food. Therefore, the
need to enhance palatability of the leaves and ensure the retention of
nutrients and phytochemicals that is relevant to the health of individuals.
Many researchers have worked on bitter leaf including determination of its phytochemicals and some
aspects of its composition but no work has been done to determine the effect of
de-bittering treatments on the nutrient composition, carotenoid contents and profile of bitter leaf, hence
the basis for this research work.
1.4 OBJECTIVE
The main
objective of this research work is to determine the effects of different
de-bittering treatments on
the nutrient composition, carotenoid
content and profile of bitter
leaf.
The specific
objectives are:
i.
To process the bitter leaf samples.
ii.
To determine the beta-carotene content and profile of
the fresh and processed
bitter leaves.
iii.
To determine the phytochemical content of the fresh and processed bitter leaves.
iv.
To determine the vitamin and mineral contents of the fresh and processed bitter leaves.
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