ABSTRACT
This work evaluated the quality properties of high-fibre bread with no-added sugar from flour blends of orange fleshed sweet potato, tiger nut, wheat and date fruit. The proximate, functional, physical properties and β-carotene of flour and bread was analyzed. The proximate composition, moisture content of the flour ranged from 16.67% (WOTD2) to 18.93% (WOTD5), ash 1.75 (WOTD2) to 2.15 % (WOTD5), crude fibre 2.47 % (WOTD2) to 2.93 % (WOTD5), protein 10.41 % (WOTD5) to 12.16 % (W1), dry matter 81.07 % (WOTD5) to 84.44 % (W1), fat 4.45 % (WOTD5) to 6.67 % (W1), carbohydrate 78.09% (WOTD2) to 80.07 % and energy value 417.77 % (WOTD2) to 401.93 % (WOTD2). Functional properties, bulk density ranged from 0.72 (g/ml) to 0.76 (g/ml), oil absorption capacity 2.75 ml/g (WOTD5) to 2.05ml/g (WOTD2), water absorption capacity 3.10 ml/g (WOTD2) to 3.70ml/g (WOTD5), foam stability 91.17 ml/g (WOTD2) to 94.44 ml/g (WOTD5), foam capacity 13.64 ml/g (WOTD2) to 16.37ml/g (WOTD5), wettability 41.00s WOTD2 to 56.50s WOTD5, gelatinization temperature 58.43 0C WOTD2 to 65.82 0C WOTD5 and gelatinization capacity 3.20 % WOTD2 to 4.88 % WOTD5. The β-carotene ranged from 2468.90 (WOTD2) to 5290.80 (WOTD5). In conclusion, the protein, fat and crude fibre contents of both the flour blends increased as orange fleshed sweet potato flour substitution increased. The partial substitution of wheat flour with orange fleshed sweet potato flour considerably improves the physicochemical and physical properties of the flours, especially protein, ash, fiber and energy, as well as functional properties. The values obtained show that the bread are good sources of energy, most nutrients are within range of the Recommended Dietary Allowance.
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 the study 1
1.2 Statement of the problem 3
1.3
Justification of the study 3
1.4 Objectives
of the study 4
CHAPTER
2: LITERATURE REVIEW
2.1 Description of wheat grains 5
2.1.1
Nutritional and health benefits of wheat grains 6
2.1.2 Processing
and food applications of wheat grains 7
2.2 Orange‐fleshed
sweet potato 8
2.2.1 Nutritional value and therapeutic benefits of
orange‐fleshed sweet potato 8
2.2.2 Antinutrient factors of orange fleshed sweet
potato 10
2.2.3 Processing and utilization of orange fleshed
sweet potato 11
2.3
Description of Tigernut 13
2.3.1 Nutritional value and health benefits of tiger
nut 14
2.3.2 Antinutritional factors in tigernut 16
2.3.3 Processing and utilization of tiger nut 17
2.4 Composite flour 19
2.5 Overview of bread 20
2.6 Sugar and its effect in bread 21
2.7 Overview of date palm: A sugar alternative 23
2.8
Nutritional and health benefits of dietary fibre 24
2.8.1 Effect of dietary fibre on shelf-life of bread 25
CHAPTER 3: MATERIALS AND METHODS
3.1 Sources
of raw materials 27
3.2 Sample
preparation 27
3.2.1
Processing of tiger-nut flour 27
3.2.2
Processing of date fruit pulp flour 27
3.2.3
Processing of orange-fleshed sweet potato flour 27
3.3 Formulation of composite flour 34
3.4 Production of bread 35
3.5 Methods of analyses 37
3.6 Determination of functional properties of
flour 37
3.6.1 Bulk density 37
3.6.2 Water
absorption capacity 37
3.6.3 Oil
absorption capacity 38
3.6.4 Foam capacity and stability 38
3.6.5 Swelling
index 38
3.6.6 Gelatinization temperature and time 39
3.6.7 Wettability 39
3.7 Determination of proximate composition of
bread samples 39
3.7.1
Moisture content 40
3.7.2
Crude protein 40
3.7.3
Ash 41
3.7.4 Fat 41
3.7.5
Crude fiber 42
3.7.6
Carbohydrate 43
3.7.7 Energy value 43
3.8 Determination of physical properties of
bread 44
3.8.1
Determination of bread weight 44
3.8.2 Determination of loaf volume 44
3.8.3
Determination of specific volume (SV) 44
3.8.4
Determination of bread height 44
3.9 Determination of β-carotene of flour and
bread 44
3.10 Sensory
evaluation of bread samples 45
3.11 Experimental design 45
3.12 Statistical analysis 46
CHAPTER
4: RESULTS AND DISCUSSION
4.1
Pictorial representation of bread samples 46
4.2
The functional properties of the Bread samples 47
4.3 The proximate Composition of the
Sample 52
4.4 The beta carotenoid content of the samples 57
4.5
Physical Properties of the Bread Samples 60
4.6
Sensory Evaluation of the Bread samples 62
CHAPTER 5:
CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 65
5.2
Recommendations 66
REFERENCES 67
LIST
OF TABLES
Table 3.1 Flour blends formulation 33
Table
3.2: Recipe for production of bread 34
Table 4.1: Functional properties of the sample 48
Table 4.2: Proximate composition of the samples 53
Table 4.3: Beta carotene composition of the Samples 58
Table 4.4: Physical properties of the bread samples 61
Table 4.5: Sensory evaluation of the bread samples 63
LIST
OF FIGURES
Figure
3.1: Process flow chart for tiger-nut flour
30
Figure 3.2: Flow
chart for the production of date palm pulp flour 31
Figure
3.3: Flow chart for production of orange-fleshed sweet potato flour 32
Figure 3.4: Flow chart for bread
production 35
LIST
OF PLATES
Plate 1: Raw materials
29
Plate 2: Bread made from
100% wheat flour 46
Plate
3: Bread made from 85% Wheat flour, 5% orange fleshed sweet potato flour, 5%
tiger nut flour and 5% date pulp flour 46
Plate
4: Bread made from 80% Wheat flour, 10% orange fleshed sweet potato flour, 5%
tiger nut flour and 5% date pulp flour 46
Plate
5: Bread made from 75% Wheat flour, 15% orange fleshed sweet potato flour, 5%
tiger nut flour and 5% date pulp flour 46
Plate
6: Bread made from 70% Wheat flour, 20% orange fleshed sweet potato flour, 5%
tiger nut flour and 5% date pulp flour 46
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
High fibre snacks are crucial for human
well-being. Main sources of fibre are whole grains, legumes, nuts, fruits and vegetables (Obasi
and Ifediba, 2018). Adequate
intake of fibre results to lower risk for developing type-2 diabetes (Yao et
al., 2014) and
obesity (Choumenkovitch et al.,
2013). Incorporating fibre to staple food products like bread is a
cost-effective means of ensuring that consumers meet the stipulated recommended
daily intake (Li and Komarek, 2017).
Bread
is a fermented snack produced by series of processes involving mixing,
kneading, proofing, shaping and baking (Dewettinck et al., 2008). It is an important staple food in both developing
and developed countries (Aider et al.,
2012). Consumption of bread has increased considerably in recent years (Rinaldi
et al., 2015) due to urbanization,
growing population and a shift in food preferences towards snacks (Ogunjobi and
Ogunwole, 2010). Bread varies in its nutrients depending on the type of
ingredients used in its preparation (Igbabul et al., 2019). It is basically made from wheat flour, yeast, fat,
sugar, salt and water (Oyetayo and Oyedeji, 2017). The fact that sugar possess
high calories with no essential nutrients, thus, causing metabolic problems
like type II diabetes and obesity necessitated its substitution with natural
sweeteners like date fruit (Peter et al., 2017).
Date palm fruit (Phoenix dactylifera)
is a functional crop (Ghinimi et al.,
2017). It possess substantial amount of fibre (Hamza et al., 2014),
antioxidant, flavonoids (Dada et al., 2012), lutein and zeaxanthin
(Farheena et al., 2015). Date fruit is an excellent source of iron, calcium,
magnesium, potassium, but minor source of vitamins A and B2 (Dada et
al., 2012; Farheena et al., 2015). Date fruit contains more than 70
% sugar mainly glucose and fructose (Dada et al., 2012). Sugars from
date fruit are easily digested and can immediately be moved to the blood after
consumption and quickly metabolized to release energy of various cell
activities (Peter et al., 2017).
The use of orange fleshed sweet potato in
bread production has been advocated for as a means of extending the value-chain
of orange-fleshed sweet potato roots and increasing its market space, thus
improving its uptake and utilization (Owade et
al., 2018). Orange-fleshed sweet potato (Ipomoea batatas)
possesses a characteristic attractive sweet taste and eye‐pleasing yellow to orange
colour (Kaguongo, 2012). It is a good source of nondigestible dietary fiber,
minerals, vitamins and antioxidants (Endrias et al., 2016; Rodrigues et al.,
2016). Most varieties of orange-fleshed sweet potato contains 3000 to 16000
µg/1000 g-1 of β-carotene and
this contributes to 250 to 1300 µg/100 g-1 Retinol Activity Equivalents (RAE) (Gurmu et al.,
2014). Orange‐fleshed
sweet potato is appreciated due to its role in eradication of vitamin A
deficiency in developing countries (Kurabachew, 2015; Girard et al., 2017).
Tiger nut (Cyperus esculenta) is an
underutilized perennial crop of the same genus as the papyrus plant (Ogbonna et al., 2013). It is known as “aya” in
Hausa; “akiawusa” in Igbo; “ofio” in Yoruba (Musa and Hamza, 2014). Tiger nut is basically cultivated for its
small tuberous rhizomes, which can be eaten raw, roasted, dried, baked or made
into a refreshing beverage (Musa and Hamza, 2013). They are rich in
carbohydrate and fats but fairly high in proteins. Tiger nut is also rich in
phosphorus, potassium, magnesium and protective nutrients such as dietary fibre
(Suleiman et al., 2018). According to
Richard and Paul (2016), one serving of tiger nuts has a whopping 10 grams of
fiber, providing almost half of the daily requirement. Tiger nuts could play important roles in providing
food security, enhancing livelihoods and improving nutritional status of
vulnerable groups (Suleiman et al., 2018).
1.2 STATEMENT OF THE PROBLEM
Bread
is basically made from ingredients like wheat flour, sugar etc. Importation of
wheat flour represent a major burden on the economy of most countries. This
burden includes loss of foreign exchange, food insecurity, as well as
displacement of local food, with detrimental effects on the agricultural and
technological development of countries like Nigeria (Ohimain, 2014). More so, Nigeria
spends most of its foreign exchange on importation of sugar. This depletes the
country’s foreign exchange reserve (Nwanekezi et al., 2015). Frequent consumption of sugary food products causes
metabolic problems which includes but not limited to type II diabetes and
obesity (Peter et al., 2017).
Vitamin
A deficiency (VAD) constitutes a major nutritional concern in the poor
communities of the developing world. It is a major contributor to the morbidity
and mortality of under-five children and can result in impaired resistance to
infection as well as increased risk of death (Olufunmilola et al., 2018).
High fibre
diets have numerous health benefits like reduction of chances of developing
obesity and type II diabetes (Choumenkovitch et al., 2013;
Yao et al., 2014).
However, most people fall short of the recommended daily requirement of dietary
fibre (Salvin, 2008).
1.3
JUSTIFICATION OF THE STUDY
Bread is a nutritious baked product that
can be consumed by children and adults. Production of bread from blends of orange fleshed sweet
potato, tiger nut, wheat and date fruit pulp will not only encourage improved
cultivation of orange fleshed sweet potato, tiger nut and date fruit but will
also enhance their economic value, reduce over reliance on wheat flour for
bread production, increase the intake of nutrient content of the crops, reduce
loss of foreign exchange used in wheat flour importation and in turn contribute
in curbing food insecurity. Individuals suffering from vitamin A deficiencies,
and those that require high fibre foods, bread producing industries and
dieticians will find bread produced in this study highly valuable. Bread
produced in this study will also be of immense benefit to victims
of metabolic problems like type II diabetes and obesity.
1.4 OBJECTIVES OF THE STUDY
The
main objective of this work was to evaluate the quality properties of
high-fibre bread with no-added sugar from flour blends of orange fleshed sweet
potato, tiger nut, wheat and date fruit.
The specific objectives were to:
i.
produce composite flour from orange
fleshed sweet potato,
tiger
nut, wheat and date fruit.
ii.
determine the functional properties of the
composite flour
iii.
produce bread using the composite flour
iv.
determine the physical properties, proximate
composition,
carotenoid
content and sensory attributes of the bread
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