ABSTRACT
The objectives of this research were to evaluate the chemical composition and sensory evaluation of sorghum flour (SF) and bambara groundnut flour (BF) on the quality of wheat bread. Bambara groundnut and Sorghum seeds were processed into flour and mixed with wheat flour in the ratio of 5:15:80, 5:20:75 and 25:25:50 for bread production. The breads were prepared by the straight dough method. Four samples of bread were produced and denoted as Sample G, H, I and J respectively. Sample G served as control with 100% wheat flour, while Sample H to J consists of composite wheat-sorghum-bambara groundnut flours in ratio of 80:15:5, 75:20:5 and 50:25:25% respectively. Analysis such as functional and chemical evaluation of flour blends were carried out to determine its suitability for bread and other confectioneries. Chemical composition, sensory properties and physical characteristics such as weight, volume and specific volume were evaluated. The result of the proximate composition showed that carbohydrate content decreased significantly (p<0.05) with increase in sorghum and bambara groundnut flour blends varying from 79.52.16 to 74.07%. The moisture, protein, ash, crude fibre and fat contents of the bread samples generally increased significantly (p˃0.05) with increase in sorghum and bambara groundnut flours. Sorghum flour only showed significantly (p<0.05) higher water holding capacity than wheat flour and bambara groundnut flour blends respectively. The physical properties of the bread loaves were evaluated. The loaf volume of composite breads decreased significantly (p<0.05) from 260.0 to 1.44cm3. Samples H to J showed a significant increase (p<0.05) in weight and specific volumes of the bread samples of 293.5-312.5g and 0.08-0.70cm3/g respectively. The mineral (Mg and P) contents of the bread samples decreased significantly (p<0.05) with increased percentages of Sorghum flour and Bambara groundnut flour in the bread. The result of the sensory properties showed that there was significant (p<0.05) difference in the taste, flavor, crumb colour and overall acceptability of the 100% wheat bread and from composite samples. The 100% wheat bread recorded the highest scores in all the parameters evaluated. However, all other samples were well accepted. Sample J showed a decrease in the values of taste, flavor and overall acceptability of the bread samples with increasing levels of sorghum and bambara groundnut flour.
TABLE
OF CONTENTS
Title page i
Declaration
ii
Certification
iii
Dedication
iv
Acknowledgements
v
Table of Contents
vi
List of Tables
x
List of Figures
xi
List of Plates
xii
Abstract xiii
CHAPTER 1: INTRODUCTION
1.1
Background of study
1
1.2 Background information
4
1.3 Justification
4
1.4 Statement of problem
5
1.5 Objectives
6
CHAPTER 2:
LITERATURE REVIEW
2.1 Wheat
7
2.1.1 Nutrient
composition of wheat 7
2.1.2 Wheat
processing
9
2.2 Sorghum 10
2.2.1 Nutrient
composition of sorghum
10
2.2.2 Sorghum
utilization 13
2.2.3 Sorghum
processing
13
2.3 Bambara groundnut 14
2.3.1 Nutrient
composition of bambara groundnut
15
2.3.2 Utilization
of bambara groundnut
18
2.3.3 Bambara
groundnut processing
19
2.4 Bread
21
2.4.1 Bread making
ingredients
21
2.4.1.1. Wheat
flour
22
2.4.1.2 Composite
flour
23
2.4.1.3 Yeast
24
2.4.1.4 Salt
25
2.4.1.5 Water
26
2.4.1.6 Sugar
27
2.4.1.7 Fats and
oil
27
2.4.1.8 Milk
powder 28
2.4.1.9
Emulsifier
28
2.4.2
Bread making process
29
2.4.2.1
Mixing
29
2.4.2.2 Proofing
30
2.4.2.3 Baking
31
2.4.3 Bread making methods
32
2.4.3.1 Straight
dough method
32
2.4.3.2 Sponge
dough method
33
2.4.3.3 Mechanical
dough method 33
2.5 Sensory properties of bread
34
2.5.1 Bread flavor
34
2.5.2 Bread texture
35
2.5.3 Colour 35
CHAPTER 3 MATERIAL AND METHODS
3.1 Raw material
procurement
36
3.2 Sample preparation
36
3.2.1 Production of
sorghum flour
36
3.2.2 Preparation
of bambara groundnut flour
36
3.2.3 Blend
formulation of composite flour and other ingredients for bread Production 38
3.3 Proximate analysis 39
3.3.1 Moisture
content determination
39
3.3.2 Ash content determination 40
3.3.3 Crude protein
content determination
41
3.3.4 Fat content determination 41
3.3.5 Crude fibre content
determination
42
3.3.6 Carbohydrate
content determination 43
3.4 Analysis of
functional properties of flours
43
3.4.1 Determination
of bulk density of flour 43
3.4.2 Determination
of foaming capacity of flours
44
3.4.3 Determination
of water and oil absorption capacity of flours
44
3.4.4 Determination
of emulsion stability of flours
45
3.5 Production of
bread
46
3.6 Mineral content
determination
48
3.6.1 Calcium and
magnesium contents determination 48
3.6.2 Phosphorus
content determination
49
3.7 Evaluation of
physical properties of bread
49
3.8 Evaluation of
sensory properties of bread
50
3.8.1 Sensory evaluation
50
3.8.2 Statistical analysis
51
CHAPTER 4
RESULT AND DISCUSSION
4.1 Proximate
composition
52
4.1.1 Proximate
composition of flour blends
52
4.1.2 Proximate
composition of bread samples 57
4.2 Functional
properties of flour blends
61
4.3 Physical
characteristics of bread samples 64
4.4 Mineral
contents of bread samples
67
4.5 Sensory
characteristics of wheat sorghum bambara groundnut breads 70
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1
Conclusion
72
5.2
Recommendations
72
References
74
Appendices 83
List
of abbreviations
84
LIST OF TABLES
2.1 Composition of wheat products per 100g
edible portion
9
2.2 Nutrient content of whole kernel and
its fraction of sorghum grains 12
2.3
Mineral composition of sorghum grains (mg/100) 12
2.4 Proximate composition of different
varieties of bambara groundnut seeds flour and seed coat
17
2.5 Mineral composition of raw bambara
groundnut (mg/100) nut 17
2.6 Comparison of nutrient composition of
some grain legumes 18
2.7 Fatty acid composition of bambara
groundnut oil
18
3.1Percentage proportion of
wheat-sorghum-bambara groundnut composite flour and recipe formulation for
bread production
39
4.1 Proximate composition of flour and blends
54
4.2 Proximate composition of wheat sorghum
and bambara groundnut Bread Samples (%) 56
4.3 Functional properties
of flour and blends 60
4.4 Physical properties
of bread samples
63
4.5 Mineral composition of the bread samples 68
4.6
Sensory properties of bread samples
69
LIST OF FIGURES
2.1 Flowchart for different processes of
preparation of bambara groundnut flour
20
3.1 Flowchart for production of sorghum flour 37
3.2 Flowchart for production of bambara
groundnut flour 38
3.3
Production of wheat sorghum-bambara groundnut flour bread 47
LIST OF PLATES
1.
Bread samples
66
2.
Bread crumb samples
66
CHAPTER
1
INTRODUCTION
1.1 BACKGROUND
OF STUDY
Bread
is defined as a confectionary baked product produced from flour, yeast, salt,
sugar and water. It involves a series of processes such as mixing, kneading,
proofing, shaping and baking (Dewettinck et al., 2008). Bread and other wheat containing baked
products are staple confectionary food in developed and developing countries.
Bread contains various nutrients such as carbohydrate, protein, fibre, vitamins
and minerals in the diets of many people worldwide (Aider et al., 2012). It is naturally low in protein and nutritionally not
a balanced diet because it is low in lysine, an essential amino acid. The
consumption of bread in Nigeria is on a steady increase because it is a ready-to-eat
food normally consumed at breakfast, and sometimes at dinner. Bread has been
one of the most appealing food products due to its nutritional characteristics
and ready-to-eat convenience (Angelino et
al., 2017). Emphasis is now made on healthy bread with protein, increased
dietary fibre intake, high resistant starch, low calorie and carbohydrate
content of baked goods.
Wheat (Triticum
aestivum), is the third most important cereal crop after maize and rice
with world production of 695 million metric tons annually (Zhang et al., 2018). Among the cereal flours,
wheat is extensively used for bread making among other uses. The unique bread
making properties of wheat flour are due to its gluten protein when hydrated,
it forms strong cohesive dough which retains gas and produces a light aerated
baked product (Delcour and Hoseney, 2010). Wheat importation has led to a huge
loss of currency and increased retail price of baked products. Due to the high
cost and high demand for wheat flour based goods, efforts are being directed
toward developing, evaluating and providing alternative formulations of flour
for bread and cookie making.
Sorghum is a cereal in the semi-arid regions of the world,
where it is an important food and feed crop. Sorghum was grown in over 44 million hectares around the
world in 2004 and the total world production was 60 million tons thereby
considering it as the fifth most important cereal in the world (FAO Statistical
database-FAOSTAT, 2010). Although, this production is only about 11-12% of each
of the major cereals such as maize, rice and wheat, the food potential of
sorghum resides in the ability of the plant to grow well in the semi-arid
regions of the world. The USA is a major producer of sorghum but the grain
is not consumed as human food except for a very small fraction as animal
fodder, whilst in Africa and Indian, the grain is a major food
source. Grain sorghum contains phenolic compounds like flavonoids which
have been found to inhibit tumour development. The starches and sugars in
sorghum are released more slowly than in other cereals and hence it could be
beneficial to diabetics (Poquette et al.,
2014). It has the potential to be processed into starch, flour, grits and
flakes and used to produce a wide range of industrial products. It can also be
malted and processed into malted foods such as beverages and beer. Sorghum
could play a pivotal role in agricultural improvement in some of the poorest
countries of the world if relevant scientific work is carried out to produce
the yield, quality and knowledge required by locally-based industries. With the
aid of proper processing technology, equipment and methods, it would be
possible to enhance the nutritional and aesthetic value of sorghum products.
Among the legumes widely cultivated in Nigeria, Bambara
groundnut (Vigna subterranea) is an
indigenous grain legume crop grown mainly by subsistence women farmers in drier
parts of sub-saharan Africa (FAO, 2001). Adu-Dapaah and Sangwan (2004),
reported that Bambara groundnut seed is completely balanced food because it
contains high iron content of 4.9-48mg/100g, compared to a range of
2.0-10.0mg/100g for most legumes, protein 18.0-24.0% with high lysine and
methionine contents, ash 3.0 to 5.0 %, fat 5.0-7.0, fibre 5.0-12.0%, potassium
1144-1935mg/100g, sodium 2.9-12.0mg/100g, calcium 95.8-99mg/100g, carbohydrate
51-70%, oil 6-12% and energy 367-414kcal/100 mg. Bambara groundnuts are
usually eaten as snack in immature stage. The dried matured seeds are boiled,
grilled or roasted. The matured dry seeds are often milled into flour and used
in the preparation of akpekpa, moimoi, okpa, akara, canned bambara
nut. Bambara groundnut could be used to complement cereal grains in order
to provide a balanced amino acid profile. Nigeria has unfavorable climatic
condition for wheat cultivation but suitable for tropical crops such as
legumes, roots, tubers and cereals. Therefore, consumption of cereal based
foods like biscuits, bread and other baked products requires development of an
adequate substitute for wheat (Kudre and Benjakul, 2013).
Composite flour technology initially referred to the process
of mixing wheat flour with cereals and legume flour to make use of raw
materials such as bread and biscuits to produce high quality products in an
economical way. According to Mohammed et
al., (2011) composite flour technology has many advantages which includes;
it plays a vital role to complement the deficiency of essential nutrients;
saves hard currency; promote high yielding local
plant species and enhances overall use of domestic agriculture. In selecting the components
to be used in composite flour blends, the materials should preferably be
readily available, culturally acceptable and provide increased nutritional
potentials. Ideally, the foods produced should look and taste like traditional
foods (Akobundu et al, 1998). The
production of composite flours using various crops for confectionary and bakery
goods have been carried out by many researchers, among which are; corn, barley
and cassava (Khalil et al., 2000),
legume flour (Sadowska et al., 2003),
peanuts and sunflower seed (Fagbemi et
al., 2005); coconut flour (Trinidad et
al., 2006). All these ingredients will impart characteristic colors,
texture and nutritional value which may be favourable in bakery products,
recipes and other food products. However very little information is available
on the composite flour of wheat/sorghum/bambara groundnut for bread production.
The Utilization of these local crops in baked products could lead to economic
enhancement through reduction of importation costs of wheat flour. In addition,
use of local crops like sorghum and bambara groundnut (Vigna subterranea) in baking will enable cheap and nutritious baked
products to become available and affordable to many.
1.2 BACKGROUND INFORMATION
This
study is targeted at exploring the best combination and potential of sorghum
and bambara groundnut flour with a mixture of wheat as composite flour in the
production of bread in order to improve the nutritional requirement or
qualities and other quality characteristics such as texture, flavor, taste,
weight and appearance which are essential parameters in the determination of
good a quality bread.
1.3 JUSTIFICATION
Bread
is an important staple food made mostly from flour that is widely consumed
throughout the world. Therefore, it is important to produce bread of good
quality characteristics that could be generally accepted and meet the daily
nutritional requirement as stipulated by the World Health Organization (WHO)
(Pomeranz, 1990). Sorghum and bambara groundnuts are potential crops to be
evaluated by blending with wheat flour for products with increased baking
qualities, human nutrition and reduced costs of production. As a result,
import costs of raw materials will be significantly reduced and malnutrition
arrested especially among Nigerian children. This research work is therefore
been carried out to evaluate the chemical composition and sensory qualities of
bread samples made from wheat-sorghum-bambara groundnut flour blends as
compared to non-blended wheat flour (control). To exploit the potentials of
sorghum, bambara groundnut and wheat composite flour in the production of bread
thereby improving it overall qualities. Encourage cultivation of sorghum and
bambara groundnut, so as to encourage it's use and nutritional value that is
desirable in our food, thereby promoting the health status of the society.
1.4
STATEMENT OF PROBLEM
Due
to the economic situation of wheat importation in Nigeria, population increase,
post harvest losses in our local food, inadequate nutritional qualities of the
sub-standard bread products in most areas of the country, the problem of
malnutrition among young Nigerian children, most Nigerians now go for plant
protein sources of food, bread with high nutritive value that would satisfy the
desiring qualities of the consumer in terms of size, weight and volume. It is
now therefore, very important to go into research and investigate these plant
materials such as Bambara groundnut and sorghum and how it can be processed
into varied products such as bread. Again, there is need to encourage wheat
substitution by looking into the suitability of flours like sorghum and bambara
groundnut for bread making, since Nigeria spend a lot in importation of wheat,
which cannot be grown here due to our weather. Therefore, to produce a good
quality bread, there is need to exploit the nutritional qualities of sorghum
and bambara groundnut in bread production, as it will go a long way in
eliminating malnutrition, reduce post harvest losses, minimize importation of
wheat, and promote a healthy society (Ogundipe, 1989). Finally, cereals in
general are deficient in essential amino acid like lysine and tryptophan. On
the other hand, legumes are deficient in sulphur containing amino acids like
methionine and cystine but rich in tryptophan and lysine. Therefore, there will
be a desirable pattern of essential amino acids of high biological value when
cereals and legumes are combined (Nnam, 2001).
1.5
BROAD OBJECTIVE
In
the light of the above, this thesis was designed to produce bread from
composites of wheat, sorghum, and bambara groundnut, thus enhancing the use of
underutilized indigenous crops in ensuring food security, combat hunger,
enhanced health, increase farming and economic activities leading to wealth
creation, thereby improving the overall quality.
The
specific objectives of this work are to:
1.
To produce flours from sorghum and bambara groundnut grains
2.
To evaluate the functional properties and chemical
composition of wheat, sorghum and bambara groundnut flour blends.
3.
To produce bread from
blends and evaluate the chemical composition and sensory properties of wheat,
sorghum and bambara groundnut bread.
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