ABSTRACT
Samples of Acacia senegal (AS), and Anacardium occidentale (AO) and Khaya senegalenses (KS) gums were analyzed for physicochemical parameters (colour, pH, solubility in water/ethanol, total dissolved solid, solubility, wave length of maximum absorption, salinity and conductivity), functional groups ( FTIR analysis), chemical constituents (GC/MS analysis) and rheological parameters. Effect of blending on the analyzed parameters for various combinations of the gums (100: 00, 80:20, 60:40, 50:50, 40:60, 20:80 and 00:100 of AS:AO, AS:KS and AO:KS, respectively) were also studied. The results of the analyses indicated that physicochemical parameters of the gums and their various composites were markedly different from the parameters obtained for the crude gum or the average of the two. The existence of interaction between the blended gums was confirmed by the spectra obtained from FTIR analysis. The spectra indicated that the wave number and intensity of IR absorption by the gum blends were shifted significantly and in some cases, some of the functional groups that were found in the original gums before blending were missing, while in others, new functional groups were formed. GC/MS results of the blended gums revealed three fold observations. Firstly, similar compounds that were found in the parent gums were identified but with different concentrations. Secondly, new compounds were found and thirdly, some of the compounds were missing. Rheological analysis was basically carried out to estimate the intrinsic viscosity and Hugginʼs constants for the studied gums and the various blends. Hugginʼs parameters displayed remarkable increment due to the blending and the range of values obtained for the Huggins constant, showed no aggregation in either of the gums or their combinations.
TABLE
OF CONTENTS
Cover
page i
Title
page ii
Declaration iii
Dedication iv
Certification v
Acknowledgements vi
Table of contents vii
List of Tables xi
List of Figures ivx
List of Plates xv
Abstract xvi
CHAPTER
1: INTRODUCTION
1.1 Background of the Study
1
1.2
Statement of the Problem 3
1.3
Aims and
Objectives of the Study
3
1.4
Justification
for the Study
4
1.5
Scope and
limitation 4
1.6 Plant Gums Chosen for the Study 5
1.6.1 Khaya
senegalensis (KS) Gum 5
1.6.2 Anacardium occidentale (AO) Gum 5
1.6.3 Acacia
senegal (AS) Gum 6
CHAPTER
2: LITERATURE REVIEW
2.1 Gums 7
2.1.1 Origin of gums 8
2.1.2 Classification of gums 8
2.1.3 Sources
of gums 9
2.2 Plant
gums 10
2.2.1. Gum
Karaya 10
2.2.2 Gum Albizia 10
2.2.3 Gum Arabic 11
2.2.4 Gum Tragacanth 11
2.2.5 Gum Anogeissus
leiocarpus 12
2.2.6 Gum from Albizia ferruginea 12
2.2.7
Ficus platyphylla 12
2.2.8 Gum Ghatti 13
2.3 Applications
of Gums 13
2.3.1 Gums as pharmaceutical
and food additives 14
2.3.2 Gums as
corrosion inhibitors 16
2.4 Functional Properties of Gums 17
2.4.1` Physical
properties of gums 18
2.5 Analytical Methods for Polymers 19
2.5.1 Measurement of viscosity: 19
2.5.2 Physiochemical Analytical Methods 20
2.5.3 Spectrophotometry methods 21
2.5.3.1 Absorption spectrophotometry 21
2.6 Composition
of Gums 22
2.7 Physicochemical
Composition of Plant Gums 24
2.8 Studies on Polymer Rheology 25
2.9 literature
on Rheology of Gums 29
2.10 Studies
on GC-MS, FTIR of Gums 34
2.11 Effect
of Electrolyte on Gum Solution 36
2.12 Effect
of pH on Viscosity of Gums 38
CHAPTER 3: MATERIALS AND METHODS
3.1 Materials 41
3.2 Tapping
of Gums 41
3.3 Purification
of the Gum 45
3.4 Physiochemical
Analysis 45
3.4.1
Determination of solubility in various solvents 45
3.4.2 Determination
of the pH 46
3.4.3 Turbidity (by absorption method) 46
3.4.4 Determination
of wavelength of maximum absorption 46
3.5
Elemental Analysis 47
3.5.1 Preparation
of stock solution of lead (1000 ppm) 47
3.5.2 Preparation
of stock solution of zinc (1000 ppm) 47
3.5.3 Preparation
of stock solution of iron (1000 ppm) 47
3.5.4 Preparation
of stock solution of magnesium (1000 ppm) 48
3.5.5
Preparation of stock solution of sodium (1000 ppm) 48
3.6 Chemical Analysis 48 3.7 FTIR Analysis 49
3.8 GC-MS
Analysis 49
3.9 Determination
of the Intrinsic Viscosities of the Gum Mucilage 50
3.10 Quality
Assurance and Control 50
CHAPTER 4: RESULTS
AND DISCUSSION
4.1 Physicochemical
Parameters 51
4.2 Elemental
Composition 59
4.3 FTIR Study 62
4.4 GCMS Study 87
4.5 Rheology 97
CHAPTER 5: CONCLUSIONS
AND RECOMMENDATION 100
References
Appendices
LIST
OF TABLES
Pages
4.1.1: Physicochemical parameters of Acacia senegal
(AS),Anacardium
occidentale (AO) and Kahaya senegalenses (KS) gums 52
4.1.2: Physicochemical
parameters of AS:AO gum blends 53
4.1.3: Physicochemical
parameters of AS: KS gum blends 54
4.1.4: Physicochemical
parameters of AO: KS gum blends 55
4.2.1:
Elemental composition of 50:50 blends of
AS, AO and KS gum
Composites 61
4 3.1: Frequencies
and peaks of IR absorption by AS gum 63
4.3.2: Frequencies
and peaks of IR absorption by AO gum 64
4.3.4: Frequencies
and peaks of IR absorption by KS gum 65
4.3.5: Frequencies
and peaks of IR absorption by 80:20 blend of AO and
AS
gums 66
4.3.6:
Frequencies and peaks of IR absorption
by 60:40 blend of AO and
AS gums 67
4.3.7: Frequencies
and peaks of IR absorption by 50:50 blend of AO and
AS gums 68
4.3.8: Frequencies and peaks of IR absorption by
40:60 blend of AO and
AS gums 69
4.3.9:
Frequencies and peaks of IR absorption
by 80:20 blend of AO and
AS gums 70
4.3.10: Frequencies and intensity of IR absorption
80:20 blend of AS and
KS gums 74
4.3.11: Frequencies and intensity of IR absorption
60:40 blend of AS and
KS gums 75
4.3.12: Frequencies and intensity of IR absorption
50:50 blend of AS and
KS gums 76
4.3.13: Frequencies and intensity of IR absorption
60:40 blend of AS and
KS gums 77
4.3.14: Frequencies and intensity of IR absorption
20:80 blend of AS and
KS gums 78
4.3.15: Frequencies and intensity (in bracket) of IR
absorption by various
composites
of AS and KS gums
79
4.3.16:
Frequencies and intensity of IR absorption by 80:20 blend of AO
and
KS gums 81
4.3.17:
Frequencies and intensity of IR absorption by 60:40 blend of AO and
KS gums 82
4.3.18:
Frequencies and intensity of IR absorption by 50:50 blend of AO and
KS
gums 83
4.3.19:
Frequencies and intensity of IR absorption by 40:60 blend of AO and
KS gums 84
4.3.20:
Frequencies and intensity of IR absorption by 20:80 blend of AO and
KS gums
85
4.3.21:
Frequencies and intensity (in bracket) of IR absorption by various
composites
of AO and KS gums 86
4.4.1: Characteristics of
suggested compounds identified from GC-MS of
AS gum 89
4.4.2: Characteristics of
suggested compounds identified from GC-MS of
AO gum 90
4.4.3: Characteristics of suggested compounds identified from GC-MS of
KS gum 91
4.4.4: Characteristics of
suggested compounds identified from GC-MS of
AS:KS composite 94
4.4.5: Characteristics of
suggested compounds identified from GC-MS of
AO:KS composite 95
4.4.6:
Characteristics
of suggested compounds identified from GC-MS of AS:AO composite 96
4.5.1: Hugginʼs parameters for the studied gums and
their composites 99
LIST
OF PLATES
Pages
3.1 Photographs
of crude gum samples
42
3.2: Photograph of KS plant 43
3.3 Photograph
of AO plant 44
4.1: Photograph
of purified gum samples
56
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE
STUDY
Plant gums are organic
substances collected from trunks or branches of the trees immediately or after physical
damage of the plant by cutting of the branch or the bark or as a result of
bacterial or fungal attack (Ahmed et al.,
2009). Generally, gums are made of high molecular weight compounds containing carbon,
hydrogen, oxygen and nitrogen as the main chain. Gums form colloidal solutions
in an appropriate solvent or swelling agent. According to Ahmad et al. (1994), most plant gums are
polyelectrolytes, which is a class of polymers that bear a large number of
ionizable groups on the main chain. Gums
have different applications in different industries. For instance, Albizia lebbeck and some Albizia zygia gums have been found to act
as natural emulsifiers for food and pharmaceuticals (Mhinzi, 2002). According
to de Paula et al. (2001), Albizia lebbeck gum exudate is also used
as an alternative for Arabic gum in mining industries. Guar and some other gums
are used in the mineral processing and mining industry (Ma and Pawlik, 2007). In
food industries, xanthan and locust
bean gums are used as thickening agents (Higiro et al., 2006). In the froth
flotation of platinum ores, guar gum is applied to regulate effect of naturally
inorganic waste minerals and talc. The function of polysaccharide is for adsorption
on talc surface which makes it soluble in water.
In the pharmaceutical firms, the functions of
Guar gum are of great importance for monitoring the drug release when ingested,
such as in the treatment of colorectal cancer and in oral rehydration solutions
(ORS) for treatment of cholera in adults (Pablyana et al., 2007). Guar gum, used
in drug is applied externally, as synthetic cervical mucus and as a visco-
supplementation agent in osteoarthritis treatment. Detarium senegalense (Gmelin gum) has been stated to be vital in food
and pharmaceutical industries, for modification of food texture and controlling
drug release respectively (Wang et al.,
1997).
The numerous uses of gums
have been found to be based on their functional properties such as physicochemical
properties, rheological properties, nutritive content, mineral element content
and phytochemical. For instance, irrespective of its suitable rheological properties, Albizia
lebbeck gum cannot be used as a food additive due to its high aluminum and
tannins level (de Paula et al.,
2001). Pablyana et al. (2007) explained that the existence of protein in
polysaccharides can stimulate an inflammation response in cells, which can prevent
the applications of gums in pharmacology. Interfacial rheology of gums has been
found to be a vital process in studying gums properties (Elmanan et al., 2008). Fenugreek gum is generally applied as thickening, water sustaining
agent, in food industries due to its high manose and galactose contents which increases
its viscosity in aqueous solution (Youssef et
al., 2009). Similarly, Rinaudo (2001) stated that the numerous applications
of gum exudates are as a result of their water sustaining ability which produces
gels, foams or highly viscous solutions. These characteristics depend on the
chemical property of gum exudates polysaccharides and their structures in the appropriate
solvent. Besides, the conformation of a
polymer system is determined by the temperature, acetyl and pyruvate content, ionic
strength and pH (Khouryieh et al.,
2007). Higiro et al. (2006), also explained
that Xanthan gum produce an association with galactose and mannose. These characteristics
enhance its application in food industry as a gel thickening agent. Menon
(2003) also found out that an important tool for determining the process
ability and applications of exudate gums is their rheological properties.
Considering the numerous
applications carried out form plant gums, several studies have been conducted
on physicochemical, rheological, proximate, cationic and polyelectrolyte
compositions of some gums. However, literature is scanty of detail properties
of composite gums produced from Acacia senegal
(AS) and Anacardium occidental (AO) and Khaya senegalenses (KS) gum exudates.
1.2 STATEMENT OF
THE PROBLEM
Gums are widely applied in some
industries including pharmaceuticals, food, binding/adhesive, pulp/paper,
metallurgical and other fields. However, several researches have led to the
conclusion that the specific application of a given gum is based on its
physicochemical, functional, rheological and other properties. An individual
gum hardly meets the requirements for all necessary applications due to their
unique properties. Therefore any approach that can be adopted to modify these
properties for better utilization will certainly enhance the applications of gums
in various aspects. Hence this research seeks to modify some physicochemical,
rheological and spectroscopic properties of some gums through blending in order
to overcome the problem of scarcity and enhance their application for
industrial and other uses.
1.3 AIMS AND OBJECTIVES
This study is aimed at characterization
and the modification of the functional properties of various composite gums
produced from Acacia senegal
(AS), Anacardium occidentale (AO) and Khaya
senegalenses (KS) gums. This aim shall be
achieved through the following objectives:
- To
obtain Acacia senegal (AS), Anacardium occidentale (AO) and Khaya
senegalenses (KS) gums from local
plantations within Nigeria,
- To
produce various composites gums using different proportions of Acacia senegal (AS), and Anacardium occidentale
(AO) and Khaya senegalenses (KS) gums blends (i.e. 80:20, 60:40, 50:50,
40:60 and 20:80).
- To
carry out physicochemical analysis on Acacia senegal (AS), and Anacardium occidentale (AO) and Khaya senegalenses (KS)
gums and their blends.
- To
carry out spectroscopic analysis (GCMS and FTIR) on Acacia senegal (AS), and Anacardium occidentale (AO) and Khaya
senegalenses (KS) gums and their
blends.
- To
identify and analyze functional properties of the studied gums that are affected
by blending.
- To
carry out rheological analysis on Acacia senegal (AS), and Anacardium occidentale (AO) and Khaya senegalenses (KS)
gums and their blends.
- To
offer useful recommendations based on the results of the study.
1.4 JUSTIFICATION FOR THE STUDY
Recently, there is a
global increase in the demands for gums as a result of its various utilizations
in pharmaceuticals and food industries, based on its physiochemical and
rheological properties. This leads to a high cost and scarcity of gums.
Consequently, there is a greater need to evaluate such characteristics in our
local plant gums to serve as a substitute with better qualities and a data base
for further analysis.
1.5 SCOPE AND
LIMITATION OF THE STUDY
This research work was designed to determine the
physicochemical parameters, spectroscopic
analysis (GCMS and FTIR), elemental analysis and viscometeric behaviors of AS, AO and KS gums
exudates and their blends (i.e. 80:20,
60:40, 50:50, 40:60 and 20:80).
1.6 PLANT GUMS CHOSEN FOR THE STUDY
1.6.1 Khaya
senegalenses gum (KS)
Khaya senegalenses
is usually known as African mahogany in English, ‘Homra’ by the Arabs, ‘Dalehi’
by the Fulanis, ‘Madaci’ by the Hausas, ‘ono’ by the Igbos, ‘ ukpa’ by the
Annangs and ‘ogonowo’ by the Yorubas. It belongs to the Family of Meliaceae Arnold and Dewet (1993). Khaya
senegalensis is a plant of about 15-30 meters in height and 1m width. It is
characterized by its constant greenish crown. The crown has darkish shiny
pinnate leaves and characteristic round dark grey capsules. The bark is dark
grey with small reddish tinged scales. The plant is widely distributed in the
riverine forest and is scattered within the highest rainfall savannah
woodlands. In the first year of growth, the seedlings develop a strong deep tap
root which makes it most drought resistant of all khaya species (Aspinall and Bhattacharjee 1970). The plant can be
planted in swampy regions as it is very resistant to flooding. It is the
dominant specie in most of its range except when removed by logging. Khaya plant is planted as an ornamental
tree. Aspinall and Bhattacharjee ( 1970), reported that Khaya gum is colourless to light brown gum, containing high
branched polysaccharides such as Dextro-galactose, Levo-rhamnose, Dextro-galacturonic
acid and 4-O- methyl-Dextro-glucoronic acid.
1.6.2 Anacardium occidentale (AO)
Anacardium occidentale tree is commonly called cashew tree. The tree grows to a height
of about 12 m but rarely exceeds 6 m on lateritic coastal sandy areas. The
leaves of the plants are simple, alternate, glabrous, and obovate-rounded at
the ends. The bark contains a profuse bitter brown fluid (resin), which turns
brownish when exposed to the atmosphere. Anacardium
occidentale gum has been found to be useful in the production of permanent
ink used for marking and printing on fabrics while the resin is used as a
varnish and preservative for fishnets. The stem of the plant can also yield an
amber-coloured gum, which dissolves partially in water forming a jelly-like
mass. It is also used in plywood, woodwork, panels, and bookbinding as an
adhesive (Elamin, 1990).
1.6.3 Acacia senegal (AS).
Acacia senegal
also known as Senegalia senegal,
Gum acacia, Gum arabic, Senegal gum and Sudan Gum Arabic, is a moderate spiky deciduous tree
belonging to the Acacia family (Mhinzi,2003) . It was introduced to
Sub- Saharan Africa from west coastal India.
In Nigeria, it is located in Kanya Babba village in Bubura local Government
Area of Jigawa State, etc. It is 5-12 meters tall and a width of about
30 cm. Acacia Senegal produces the world's best quality Arabic gum known as Hashab gum. A. Senegal gum is used in pharmaceuticals, food additive, crafts
work, and in cosmetics. It is obtained by tapping the bark ( Elamin, 1990).
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