ABSTRACT
Composite breads were made by supplementing wheat flour (WF) with chemically modified African yam bean starch (AYBS) and Cassava starch (CS) after the starch were produced from the cleaned seeds and roots using hammer milling system. The blends (WF/AYBS/CS 80/10/10, 80.83/10.83/8.33, 85/10/5, 82.5/10/7.5, 82.5/12.5/5, 80/13.5/6.5, 80.83/13.33/5.83, 82.50/12.5/5, 81.67/11.67/6.67, 80/12.5/7.5, 81/13.5/5.5, 83.33/10.83/5.83, 80/15/5, 84.5/10/5.5) was obtained from the D-Optimal Mixture Design of Response Surface Methodology. The Functional properties of the flour/ starch blends, Physical and Sensory evaluation of the bread was determined and subjected to Statistical Analysis of Variance (ANOVA) using models comprising the Mean, Linear mixtures, Quadratic, Special cubic and Cubic and the general acceptability determined using spider plot design of Microsoft Excel System. The models and the model terms (interactions) were judged for significance at 95% confidence intervals (p<0.05). The flour/ samples had functional properties ranging from 5.66 to 7.44 pH, 6 to 8.85%w/n Least gelation concentration, 60 to 72 0C Gelation temperature, 3.86 to 4.84 % Moisture content, 0.43 to 0.52 g/cm3 Bulk density, 61 to 74.42 ml/g Water absorption capacity, 66 to 77.5 ml/g Oil absorption capacity, 2 to 5.75 % Swelling power, 1.15 to 8.1 % Swelling volume, 28.51 to 62.5 % Solubility and 15.55 to 26.25 cp Viscosity. The physical properties of the bread samples range from 0.7 to 3.2 cm Oven spring, 3.5 to 6.4 cm Height, 266.7 to 442.05 g Weight, 254.71 to 764.14 cm3 Loaf volume, 0.74 to 2.34 cm3/g Specific volume and 0.43 to 1.36 g/cm3 Bulk density. The sensory evaluation results showed that all the bread samples had high rating for all the parameters evaluated except 85/10/5% of AYBS and CS supplementation. The 84.5/10/5.5% and 80/12.50/7.5% of AYBS and CS supplementation compared better than other substitution levels which were generally acceptable as they were neither liked nor disliked by the judges. The result for the optimization of all the attributes evaluated for adequate models and model terms suggested that the blend 82.00/10.88/7.13 of AYBS and CS supplementation will satisfy all the desirable goals for optimization with the desirability value of 0.68.
TABLE OF CONTENTS
Title
page i
Declaration ii
Certification iii
Dedication iv
Acknowledgments v
Table
of contents vi
List
of tables ix
List
of figures x
List
of plates xii
Abstract xiii
CHAPTER 1: INTRODUCTION
1.1 Background
of the Study 1
1.2 Statement
of The Problem 3
1.3 Justification 4
1.4 Objectives 5
CHAPTER 2: LITERATURE
REVIEW
2.1 Wheat
(Triticum aestivum) 6
2.1.1 Utilization
and nutritional quality of wheat 6
2.2 The African
yam bean 7
2.2.1 Nutritional
value of African yam bean 8
2.2.2 Economic
importance of African yam bean 10
2.2.3 Factors
militating the utilization of African yam bean 10
2.2.4 Detoxification
of African yam bean 12
2.2.5 African
yam bean products and utilization 13
2.3 Cassava (Manihot esculenta Muell) 15
2.3.1 Description of cassava 16
2.3.2 Origin
of cassava 16
2.3.3 Economic
importance 18
2.3.4 Nutritional
profile 19
2.3.5 Uses
of cassava 20
2.4 Starch
modification 21
2.4.1 Compositions
of natural starch 21
2.4.2 Reactions
of natural starch under basic conditions 23
2.4.3 Esterification
of starch 26
2.5 Composite
flour 30
2.5.1 Baking
31
2.6 Optimization 32
2.6.1 Statistical
optimization; response surface methodology 35
2.6.2 Response
surface functions 37
CHAPTER 3: MATERIALS
AND METHODS
3.1 Materials/
sources of materials 38
3.2 Sample
preparation 39
3.2.1 Preparation
of modified starches 41
3.2.2 Production
of wheat flour 42
3.2.3 Experimental
design 43
3.2.4 Determinant
of adequacy (significance) of models 44
3.2.5 Optimization
process 45
3.2.6 Formulation
46
3.3 Functional
properties of the starch – flour samples 46
3.3.1 Determination
of pH 47
3.3.2 Determination
of ash content 47
3.3.3 Least gelation concentration 47
3.3.4 Determination
of moisture content 48
3.3.5 Bulk density (BD) 48
3.3.6 Water absorption capacity (WAC) 48
3.3.7 Oil absorption capacity (OAC) 49
3.3.8 Determination
of swelling volume, swelling power and solubility 49
3.3.9 Determination
of viscosity 50
3.4 Physical characteristics of bread 50
3.4.1 Height
determination 50
3.4.2 Oven spring 50
3.4.3 Loaf
weight 50
3.4.4 Loaf
volume 50
3.4.5 The
specific volume 51
3.4.6 The bulk density 52
3.5 Sensory
evaluation 52
3.6 Statistical
analysis 52
CHAPTER 4: RESULTS AND
DISCUSSIONS
4.1 Functional
properties of the flour – starch samples 53
4.1.1 pH of
the starch samples 53
4.1.2 Least gelation
concentration (LGC) 57
4.1.3 Gelation
temperature (GT) 59
4.1.4 Moisture
composition 62
4.1.5 Bulk
density 65
4.1.6 Water absorption
capacity (WAC) 68
4.1.7 Oil
absorption capacity (OAC) 70
4.1.8 Swelling
power (SP), swelling volume (SV) and solubility (S) 73
4.1.9 Viscosity 78
4.2 Physical
characteristics of the bread samples produced from the flour –
starch
blends 82
4.2.1 Bread
height 82
4.2.2 Oven
spring 85
4.2.3 Loaf
weight 86
4.2.4 Loaf
volume and specific volume 88
4.2.5 Bulk
density 92
4.3 Sensory
evaluation of the bread samples produced from the
flour
– starch blends 93
4.3.1 Appearance 94
4.3.2 Crumb
and crust 97
4.3.3 Taste 99
4.3.4 Aroma 101
4.3.5 Determination of general acceptability of
the bread produced from
flour – starch composite 103
4.4 Optimization
of the functional properties of the flour/ starch blends, sensory
and
physical characteristics of its composite bread 106
CHAPTER 5: CONCLUSION
AND RECOMMENDATIONS
5.1 Conclusion 109
5.2 Recommendations 109
References 110
Appendix
129
LIST OF TABLES
3.1: Mixture formulations of wheat: AYB: cassava blends
from D-optimal 43
model of response surface methodology
3.2: Goals of optimization process 45
4.1:
Functional compositions of the flour – starch blend 55
4.1a:
Mixture linear model for pH 56
4.1b:
Mixture cubic model for least gelation concentration 58
4.1c:
Mixture linear model for gelation temperature 61
4.1d:
Mixture quadratic model for moisture composition 64
4.1e:
Mixture linear model for bulk density 67
4.1f:
Mixture special cubic model for water absorption capacity 69
4.1g:
Mixture special cubic model for oil absorption capacity 72
4.1h:
Mixture linear model for swelling power 75
4.1i:
Mixture linear model for swelling volume 75
4.1j:
Mixture cubic model for solubility 76
4.1k: Mixture
linear model for viscosity 79
4.2: The physical analyses
of composite bread samples produced from 83
flour – starch
4.2a:
Mixture linear model for bread height 84
4.2b:
Mixture linear model for oven spring 85
4.2c:
Mixture cubic model for loaf weight 87
4.2d:
Mixture special cubic model for specific volume 89
4.2e:
Mixture linear model for loaf volume 90
4.2f:
Mixture quadratic model for bulk density 92
4.3: The sensory evaluation
of composite bread samples produced from 95
flour
– starch blends
4.3a:
Mixture cubic model for appearance 96
4.3b:
Mixture cubic model for crumb and crust 98
4.3c:
Mixture cubic model for taste 100
4.3d:
Mixture cubic model for aroma 102
4.3e:
General acceptability of the flour/ starch composite bread 104
LIST
OF FIGURES
2.1: Chemical structures of amylose and
amylopectin 22
2.2:
Nitration of starch 27
2.3:
Acylation by carboxylic acid chloride 29
3.1: Flow chart for the production of
native cassava starch 39
3.2: Schematic diagram for the production
of African yam bean starch 40
3.3: Flow chart of modified starches 41
3.4:
Flow chart for the production of wheat flour 42
4.1:
3D Plot showing the effect of wheat flour, african yam bean starch and 56
cassava starch on pH
4.2:
3D Plot Showing the Effect of Wheat Flour, African Yam Bean Starch and 59
Cassava Starch on Lgc
4.3:
3D plot showing the effect of wheat flour, African yam bean starch and 62
cassava starch on gelation
temperature
4.4:
3D plot showing the effect of wheat flour, African yam bean starch and 65
cassava starch on moisture
composition
4.5:
3D plot showing the effect of wheat flour, African yam bean starch and 67
cassava starch on bulk density
4.6:
3D plot showing the effect of wheat flour, African yam bean starch and 70
cassava starch on water absorption
capacity
4.7:
3D plot showing the effect of wheat flour, African yam bean starch and 72
cassava starch on oil absorption
capacity
4.8:
3D plot showing the effect of wheat flour, African yam bean starch and 76
cassava starch on swelling power
4.9:
3D plot showing the effect of wheat flour, African yam bean starch and 77
cassava starch on swelling volume
4.10:
3D plot showing the effect of wheat flour, African yam bean starch and 77
cassava starch on solubility
4.11:
3D plot showing the effect of wheat flour, African yam bean starch and 80
cassava starch on viscosity
4.12:
3D plot showing the effect of wheat flour, African yam bean starch and 84
cassava starch on bread height
4.13:
3D plot showing the effect of wheat flour, African yam bean starch and 86
cassava starch on oven spring
4.14:
3D plot showing the effect of wheat flour, African yam bean starch and 88
cassava starch on loaf weight
4.15:
3D plot showing the effect of wheat flour, African yam bean starch and 91
cassava starch on loaf volume
4.16:
3D plot showing the effect of wheat flour, African yam bean starch and 91
cassava starch on specific volume
4.17:
3D plot showing the effect of wheat flour, African yam bean starch and 93
cassava starch on bread density
4.18:
3D plot showing the effect of wheat flour, African yam bean starch and 96
cassava starch on appearance
4.19: 3D plot showing the effect of wheat flour, African yam
bean starch and 98
cassava
starch on crumb and crust
4.20: 3D plot showing the effect of wheat flour, African yam
bean starch and 100
cassava
starch on Taste
4.21: 3D plot showing the effect of wheat flour, African yam
bean starch 102
and cassava
starch on Aroma
4.22: Spider plot showing the general acceptability of
bread samples 105
4.23:
Plot of desirability of the optimized blend (Desirability = 0.68) 107
LIST OF PLATES
3.1:
Wheat grain 38
3.2:
African yam bean 38
3.3:
Cassava 38
4.1: A: 80% Wheat: 10% AYB Starch: 10%
Cassava Starch, B: 80.83% Wheat: 81
10.83%
AYB Starch: 8.33% Cassava Starch, G:
80.83% Wheat: 13.33% AYB
Starch:
5.83% Cassava Starch, H: 82.5%
Wheat: 12.5% AYB Starch: 5%
Cassava
Starch, M: 80% Wheat: 15% AYB
Starch: 5% Cassava Starch,
N: 84.5% Wheat: 10%
AYB Starch: 5.5% Cassava Starch
4.2: C: 85% Wheat: 10% AYB Starch: 5%
Cassava Starch, D: 82.5% Wheat: 10% 81
AYB
Starch: 7.5% Cassava Starch, I:
81.67% Wheat: 11.67% AYB Starch:
6.67%
Cassava Starch, J: 80% Wheat: 12.5%
AYB Starch: 7.5% Cassava Starch
4.3: E: 82.5% Wheat: 12.5% AYB Starch: 5%
Cassava Starch, F: 80% Wheat: 81
13.5%
AYB Starch: 6.5% Cassava Starch, K:
81% Wheat: 13.5% AYB Starch:
5.5%
Cassava Starch, L: 83.33% Wheat:
10.83% AYB Starch: 5.83% Cassava
Starch
4.4: A: 80% Wheat: 10%
AYB Starch: 10% Cassava Starch, B:
80.83% Wheat: 108
10.83%
AYB Starch: 8.33% Cassava Starch, C:
85% Wheat: 10% AYB
Starch:
5% Cassava Starch, D: 82.5% Wheat:
10% AYB Starch: 7.5% Cassava
Starch,
E: 82.5% Wheat: 12.5% AYB Starch: 5%
Cassava Starch, F: 80%
Wheat:
13.5% AYB Starch: 6.5% Cassava Starch
4.5: K: 81% Wheat: 13.5% AYB Starch: 5.5%
Cassava Starch, L: 83.33% 108
Wheat:
10.83% AYB Starch: 5.83% Cassava Starch, M:
80% Wheat: 15% AYB
Starch:
5% Cassava Starch, N: 84.5% Wheat:
10% AYB Cassava Starch:
5.5%
Starch
4.6: G: 80.83% Wheat: 13.33% AYB Starch:
5.83% Cassava Starch, H: 82.5% 108
Wheat:
12.5% AYB Starch: 5% Cassava Starch, I:
81.67% Wheat: 11.67%
AYB
Starch: 6.67% Cassava Starch, J: 80%
Wheat: 12.5% AYB Starch: 7.5%
Cassava
Starch
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
It
is paramount to understand the nutrient, functional, toxic substances and the
anti-physiological substances composition and organoleptic properties of
locally available foods in any community or country. Adequate background
information and the usage of local foods can go a long way in aiding to solve
the problem of food unavailability and eliminate malnutrition. Reports
established that fighting against malnutrition in developing countries should
likely be centered on the adequate use of mixtures of cereals, tubers and
legumes indigenous to her (Nnam, 2003). Urbanization has been found to cause people
to forget their traditional foods and patronize convenient foods which are most
of the times nutritionally inadequate and unpurchaseable.
Starch
is the mostly used biodegradable polymer whose usage has been found to be
increasing geometrically in many branches of industry because of its respective
physicochemical properties (Yu et al., 2010).
It occurs naturally in grains, fruits, roots and tubers of most plants which
also act as their major storage material. It can be found in potatoes, corn,
wheat and rice using separation process method. Chemically, starch is made up of
two polysaccharides of note: the linear amylose type, wherein the units of 𝛼-𝐷
glucopyranose are linked with 𝛼 (1→4)–glycosidic
bonds, and the branched amylopectin whose additional 𝛼 (1→6)
glycosidic bonds are contained in the carbon chain (Biliaderis, 1991; Kaur et al., 2012).
Report
has it that native starches despite the fact that their sources are undesirable
many applications in the industry because of the chemical compositions inherent
in them are not able to withstand some condition of processing such as maximum
temperature (causes inadequate thermal resistance), diverse pH, and higher
shear rate (causes inadequate shear resistance) (Singh et al., 2007), loss
of viscosity, high tendency of retrogradation, syneresis and thickening power during
cooking and storage especially at low pH. Studies indicated that native
starches produce pastes of poor stability which thereby decreases their shelf
stability (stability during storage) which causes shrinkages and release of
water from the matrices (Tester et al., 2004). To improve on the
desirable functional properties and overcome its limitations, native starches
are often modified. Modification (alteration of the chemical and physical components
to improve structural characteristics) can be used to improve significantly the
inherent poor physicochemical properties of native starches improving its
utilization by specific industries (Cock, 1982; Miyazaki et al., 2006).
Starch
modification can be classified into four major classes namely: physical,
chemical, enzymic and biological modifications. Among these modification methodologies,
the chemical type is the most used process (Daramola and Osanyinlusi, 2006).
Chemical modification process of starch involves the treatment of native starch
with specific chemical reagents. This definition includes acetylated, oxidized,
pyrodextrinized, hydroxypropylated and cross-linked starches (Kaur et al., 2004).
The
grain size of the starch also affects its reactivity. The larger the grains
are, the higher the susceptibility to modification. This is because the larger
the grains, the easier the external factors access to them (Lewandowicz and
Mączynski, 1990).
Recently
there is great shift of interest to the physical modifications of starch (like radiation
as well as high and low temperature treatment conditions), on the industrial
perspective, chemical modifications are still the most frequently used. Among
the lists are three basic reactionswhich includes: oxidation, esterification,
and etherification (Tomasik and Zaranyika, 1995; Tomasik and Gladkowski, 2001).
One such legume and tuber of interest is African yam bean (Sphenostylis
stenocarpa) (AYB) and cassava (Manihot
palmata Muell).
African
yam beans (AYB) are an herbaceous leguminous plant occurring throughout
tropical Africa {United States Department of Agriculture (USDA), 2007}. It is widely
grown as a minor crop coupled with yam and cassava. African Yam Bean can serve
as a security crop; it has the capacity to supply year-round protein
requirements if grown on a large amount {World Health Organization (WHO), 2002}.
African yam beans (AYB) are highly nutritious with high amounts of protein, fibre,
mineral and contents. Its protein content has been found to be similar to that
of some major and commonly consumed legumes. Its amino acid profile compares,
if not better than those of cowpeas, soy beans and pigeon peas (Obizoba and
Souzey, 1989; Ene-Obong and Carnovale, 1992; Uguru and Madukaife, 2001). It
contains high metabolic energy, low true protein digestibility (62.9%) and
moderate mineral content. The amino and fatty acids contents are comparable to
those of most edible pulses (Nwokolo, 1987; Uguru and Madukaife, 2001).
It contains a higher water absorption capacity when compared to cowpeas
(Achinewhu and Akah, 2003).
The
most common starchy food sources are wheat, corn, cassava/tapioca, rice and potato.
Cassava has been reported as second only to sweet potato as one of the most
important starchy root crops in the tropics (Grace, 1977). It is grown widely
as food crop majorly for food and commercial purposes. In Nigeria, cassava is a
staple food for both rural and urban areas and in recent years it has been
transformed from being a subsistent crop to an industrial cash crop. The major
use of cassava is the traditional food processing in the house or in
small-scale cottage operations. Apart from the traditional foods, there is
great demand for cassava products which include raw materials like modified
starches for the food, beverages, pharmaceutical and textile industries amongst
others. Currently, increased production of cassava chips is being advocated for
export and incorporation of 10% cassava flour into wheat flour as composite for
bread baking (Bertolini et al.,
2001).
1.2 STATEMENT OF THE PROBLEM
Studies
have shown that in spite of the good attributes of African yam bean, it is
underutilized and rarely consumed in urban and rural areas in Nigeria. Its
current status as a minor crop means that its potential is largely unexploited.
Successful productions have been done with Wheat has been the most suitable
flour for baking due to its gluten compositions, but it has been ascertained
that wheat is not in relative abundance and hence partial replacement of some
proportions of the wheat up to 30% is highly recommended. Modified African yam
bean and cassava starches developed from native crops should serve as a better
substitute.
Different
authors have tried to understand what kind of modification is responsible for
the baking properties of the cassava starch. Some attributed this property to
the enzyme and the partial acid modifications of the starch as well as the
presence of some bacterial exopolysaccharides produced during the fermentation
(Camargo et al., 1988; Lacerda et al., 2005). However, these factors
have not been proved to be responsible for the baking behaviour. Others stated
that the UV wavelengths as well as the lactic acid fermentation are essential
for the baking expansion ability of the starch (Bertolini et al., 2001; Vatanasuchart, 2005). However, in their study with
cassava starch samples using native, fermented sun-dried and oxidized starches,
Demiate et al. (2000) associated the
high expansion of the baking characteristics to the carboxylate groups on the
chemically treated starches. As the structural modification of sun-dried starch
were made detectable by the oxidation, it may be possible to obtain other
sensory and functional potentials of the fermented starch by some other form of
modifications.
1.3 JUSTIFICATION
The
study would provide information on the functional and sensory properties of
chemically modified African yam bean (AYB) and cassava starches. The wheat/ starch bread made from
African yam bean and cassava would be a form of dietary diversification, which
will enhance African yam bean and
cassava food use and contribute to ensuring food security and sustainability in
Nigeria. It may also stimulate local
production and create employment for rural population. It will also minimize
the level of post-harvest losses, which may be useful to food industries,
institutes and homes on improving the methods of processing and preservation of
products made from indigenous food materials. The study would serve as baseline information for researchers in this area.
1.4 OBJECTIVES
The
main objective of this study was to evaluate and optimize the physicochemical properties
of wheat flour and chemically starches from modified African yam bean and
cassava.
Specific
objectives are to:
a. Produce
starches from African yam bean and cassava and to chemically modify the
starches using esterification (acetylation) method to improve their qualities
b. Formulate
composite blends of African yam bean and cassava starches and wheat flour at
different substitution levels obtained from optimal mixture model of response
surface methodology (RSM)
c. Determine
the functional properties of the wheat – starch composite flour blends
d. Produce
bread from wheat – starch composite blends
e. Determine
the physical characteristics and the sensory properties of the breads produced
from the formulated blends
f. Optimization
of the formulated blends
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