ABSTRACT
The use of composite flour for commercial bread baking purposes and consumption is increasingly gaining much attention in Nigeria. This study investigated and optimized the impact of baking temperature, time, moisture content and mix ratios on bread quality by mixing wheat with composite cassava-soybean flour at ratios; (100:0, 90:10, 80:20, 70:30, 60:40, and 50:50 respectively). Dough of different mix ratios were kneaded and allowed to proof at room temperature and baked at varying temperature and time in order to ascertain the optimal Thermophysical properties. Linear programming model was employed to optimize cost of resources used in baking. Sensory attributes (Taste, Aroma, Aftertaste, Mouthfeel, Crumbcolour, Crustcolour, Texture, Appearance and Overall acceptability) were evaluated, samples were significant at (P<0.05). Increase in cassava-soybean flour substitution level up to 50% wheat replacement produced acceptable bread at 63.22% acceptability. Crumb hardness and crust colour was affected with increased baking temperature and time. Decreases, however, were noted in all sensory attributes as substitution level increased. Baking was carried out at temperature range of 195 to 245oC. Analysis of variance was carried out using SPSS Software Version 16, to determine acceptance level. Central composite design was carried out using Design-Expert Software Version 8, to determine optimal baking temperature, time, moisture content, weight and volume of loaves at various mix ratios, the following results for ≤ 100g mix were deduced; 220oC, 15.06 minutes, 8.87%, 85.45g and 707.15cm3 for 90:10 mix ratio; 220oC, 16.33 minutes, 6.46%, 87.20g and 624.85cm3 for 80:20 mix ratio; 222.50oC, 17.16 minutes, 6.06%, 94.96g and 573.80cm3 for 70:30 mix ratio; 222.50oC, 17.35 minutes, 7.12%, 87.4g and 558.18cm3 for 60:40 mix ratio respectively. This study optimized relevant variables using experimental and analytical procedures. This study has shown the role of thermophysical properties in increased and sustainable food production in Nigeria.
TABLE OF CONTENTS
Approval Page i
Certification ii
Dedication iii
Acknowledgements iv
Abstract v
Table of contents vi
List of Tables ix
List of Figures xi
Nomenclature xiv
1.0 INTRODUCTION
1.1 Problem Statement 2
1.2 Project Aim 2
1.3 Specific Objectives 3
1.4 Scope of Research 3
1.5 Significance of the Study 3
2.0 LITERATURE REVIEW 4
3.0 MATERIALS AND METHODS
3.1 Materials 19
3.2 Methods 19
3.3 Process Technology for Cassava Flour 19
3.4 Process Technology for Soybean Flour 19
3.5 Data Collection Process 22
3.6 Baking experiment 23
3.7 Determination of thermal and physical properties 23
3.8 Optimal drying temperature and time 23
3.8.3 Effects of Natural Drying 24
3.9 Sensory evaluation of bread from blends of wheat/cassava/soybean flours 25
3.11 Linear Programming Model for Cost Optimization 28
3.12 Relations used to obtain energy and labour cost 32
3.13 Thermal analysis of CWCS dough 35
3.14 Process of heat transfer to dough 40
4.0 RESULTS AND DISCUSSIONS
4.1 Temperature 41
4.2 Time 42
4.3 Physical properties of breads from composite flours blends 42
4.4 Moisture content 43
4.5 Mix ratio 43
4.6 Loaf size 43
4.7 Time – Temperature Advantage on the Product
Quality of CWCS Bread 43
4.8 High Quality Cassava Flour (HQCF) 44
4.9 Mix Strength Determination of Dough 44
4.10 Thermal Computations 44 4.11 Data Presentation 47
4.12 Central composite designs of Response Surface Methodology 55
4.13 Effects of central composite design optimality on different mix ratios 68
4.14 Economy of scale of composite wheat, cassava and soybean bread production 70
4.15 Plastic Limit Test 71
4.16 Sensory evaluation of bread samples 73
4.17 Contributions to Knowledge 73
5.0 COST ESTIMATE FOR SETTING UP A CWCS BAKERY IN NIGERIA
5.1 Cost Requirements for Setting up a CWCS Bakery in Nigeria 74
5.2 Break-Even Analysis 75
5.3 Return on Investment 78
6.0 CONCLUSION AND RECOMMENDATIONS
6.1 Conclusion 80
6.2 Recommendations 81
REFERENCES 82
APPENDIX 88
CHAPTER ONE
1.0 INTRODUCTION
In recent time, bread consumption is continuously increasing in many of the developing countries, such as Nigeria.
There are four main reasons for this trend, namely;
- A steadily growing population.
- Changes in eating habits.
- An overall increase in income, which meant that a higher proportion of the income could be spent on fast foods, such as bread. (FAO, 1970).
- Changes in work habits and styles.
In these countries, the wheat flour needed for baking bread, rolls and pastry goods are imported, as the climatic conditions and soil nature do not favour commercial growing of wheat locally, but, the rising importation of wheat has had an increasingly adverse effect on their balance of trade. For these reasons, the Food & Agriculture Organization, FAO and government of these developing countries are collaborating on the possibility of replacing/reducing the wheat content needed for making baked goods and also paste, wholly or partly with flour obtained from locally grown substitutes. Possible sources are tuberous plants rich in starch such as cassava, yam, sweet potatoes, protein-rich flours such as soybean, peanuts and bambara nut and other cereals including maize, rice, millet and sorghum.
Although it is well known that no other crop can achieve the gluten property of wheat, composite flours from other crops have become the subject of numerous studies as possible additives to wheat, particularly for the developing countries. The use of composite flours has the following advantages, namely;
- A saving of hard currency.
- Promotion of high-yielding, native plant species.
- A better supply of protein for human nutrition.
- Better overall use of domestic agricultural production (Bugusu et al., 2001).
The advantages offer great incentives for economic growth and job creation in Nigeria.
Till date, most Nigerians have not been introduced to other types of bread apart from that made from 100% wheat flour. To cut the nation’s expense on wheat importation and find wider utilization for the locally produced cassava tuber, the federal government mandated the use of composite flour for baking. (Shittu et al., 2007). To ensure the commercial success of this composite wheat cassava soy flour technology, systematic studies need to be conducted to fully understand the best way to formulate the composite mixture and to determine the optimal processing conditions required to realize high quality baked products.
Fewer small and medium scale bakeries that use automated devices exist presently in the country (Idowu et al., 2002). The baking duration varied widely among bakers while fueling of ovens and temperature control are done using highly subjective means developed by these bakers through long time baking experience, At present, there is lack of systematic studies to understand the behaviour of composite wheat cassava soy dough under processing conditions encountered in bakeries. Such studies will assist in the design and development of appropriate process for making baked product from composite wheat cassava soy flour and also guide in the design of interim training program for successful application of composite wheat cassava soy flour technology by the bakers in the country.
- Problem Statement
Since 1st January, 2005 when Nigeria enacted a directive that makes inclusion of cassava flour mandatory in order to support the local cassava crop production and reduce importation cost of wheat, several issues still hinder full compliance to this directive. Thermal behavior of the cassava integrand on combined wheat substrate is yet to be understood by bakers. Due to lack of information about; thermophysical properties, mixing strength, fast fermentation and sensory attributes, there is still difficulty in integrating cassava flour into wheat flour for bread baking. Till date, Nigerians still rely heavily on whole wheat flour for bread baking, leaving cassava roots not fully put to use, which leads to huge capital flight waste on importation.
1.2 Project Aim
The quality of composite wheat cassava soybean bread is a function of temperature, time, moisture content and mix formulation of flour used. This study is intended to determine how these thermophysical variables influence the physical properties (volume, density, specific volume etc) and sensory attributes of composite wheat cassava soybean bread.
The research focuses towards getting the optimal mixing ratio, baking time and temperature, moisture content and to prevent fermentation in order to eliminate odour.
1.3 Specific Objectives
This work will formulate improved composite flours from blends of wheat cassava and soybean flour for increased and sustainable production, thus ensuring food security. The specific objectives include to;
- Formulate a mix ratio with correct proportion of composite wheat, cassava and soybean flour.
- Determine the optimal drying temperature and time for high quality cassava flour.
- Determine the influence of the different variables (temperature, time, moisture content and mix ratios) on composite wheat, cassava and soybean bread quality of different mix ratios.
- Determine the optimal mix strength, baking time and temperature for composite flours integration into bread baking in Nigeria.
- Develop an algorithm for minimizing cost of resource utilization for composite wheat cassava and soybean bread production.
1.4 Scope of the Research
This research work, concentrated on the following;
- Drying temperature and time of cassava and soybean flour.
- Baking temperature and time of composite wheat cassava and soybean bread.
- Evaluation of sensory attributes and thermophysical properties of composite wheat cassava and soybean bread.
- Small scale laboratory production of composite wheat cassava and soybean bread.
1.5 Significance of the Study
The results of this research would be a great relieve to Nigerians in particular and Africans at large, who could not afford the high cost of wheat flour and its baked products. This research is geared towards addressing some of the challenges outlined in the problem statement and proffer solutions to them. Integrating composite cassava and soy flour into bread baking is necessary for wider utilization of cassava roots, since cassava production is on the increase and as well the cost of wheat flour, keeping bread off the reach of low income earners.
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