ABSTRACT
Micronutrient malnutrition continues to be a problem in developing countries. Food to food fortification which includes composite flour formulation is one of the methods used to reduce the problem. However, the effectiveness of the composite flours is questionable due to the presence of antinutrients in the raw materials used. Therefore, the current study aimed at developing a nutritious, shelf-stable porridge composite flour from maize, sorghum, grain amaranth, baobab and orange-fleshed sweet potatoes. Nutrient composition data of each ingredient was generated using standard analytical methods and used in the formulation of the composite flours using Nutrisurvey software. To produce various formulations of composite flours with maize and sorghum as the cereal base and grain amaranth, baobab and OFSP as the fortifiers, a completely randomized study design in factorial arrangement with ingredient ratio and extrusion as variables and seven levels was used. Half of each of the formulations were extruded at 160 °C. Nutritional and anti-nutritional profiling followed by sensory evaluation of the composite flours was done. A comparative analysis of acceptability was performed between the best formula and the commercial composites. Stored in kraft paper and plastic containers, the two best formulations, extruded and non-extruded were subjected to real- time shelf-life studies at 20 °C, 30 °C and 40 °C. The data were analyzed using the R Project for Statistical Computing, R-3.6.3 and inferential statistics done by ANOVA and the means separated using Turkey’s HSD test. The protein content (8.99 ± 1.03 g/100 g), beta-carotene content (895.90 ± 346.85 µg/100 g), iron content (11.81 ± 9.73 mg/100 g) and zinc content (1.74 ± 0.18 mg/100 g) were improved by fortification of maize-sorghum blends on average. An increase in grain amaranth increased the phytate content. The protein content, beta-carotene content and antinutrients were decreased by 4.7%,40.9% and 35% respectively by extrusion. Consumer acceptability studies showed that the colour, flavour and overall acceptability of the composites (mean 5.7-7.4 on a 9-point hedonic scale) were affected by formulation, with the most acceptable being those containing more sorghum. The comparative study showed that the new formulations had the potential of being accepted. Compared to plastic, the formulated composites stored in Kraft paper were found to degrade faster. The formulations can retain their quality and safety for six months in various ecological zones in both kraft and plastic. Therefore, locally available ingredients such as grain amaranth, Baobab and OFSP improves the nutrient composition of maize-sorghum composites while processes such as extrusion reduce antinutrients and have a detrimental effect on beta carotene. Extrusion should be used in baby food. Bioavailability studies on zinc and iron should be conducted to ascertain the effectiveness of extrusion on the reduction of antinutrients. Refortification of extruded flours with beta carotene is recommended.The Ministry of Agriculture, Livestock and Fisheries in collaboration with the Ministry Health can promote these local crops for consumption by the Kenyan population to reduce micronutrient malnutrition.
TABLE OF CONTENTS
DECLARATION ii
PLAGIARISM DECLARATION FORM iii
ORIGINALITY REPORT iv
DEDICATION v
ACKNOWLEDGEMENTS vi
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF APPENDICES xiii
ABBREVIATIONS AND ACRONYMS xiv
OPERATIONAL DEFINITIONS xv
GENERAL ABSTRACT xvi
CHAPTER ONE: INTRODUCTION
1.1 Background 1
1.2 Statement of the problem 3
1.3 Justification 3
1.4. Objectives 4
1.4.1 Overall Objective 4
1.4.2 Specific Objectives 4
1.5 Hypothesis 4
CHAPTER TWO: LITERATURE REVIEW
2.1 Maize production and chemical composition 5
2.1.1 Origin, classification and maize production 5
2.1.2 Nutritional value and uses of maize 6
2.1.3 Maize anti-nutrients 8
2.2. Sorghum production and chemical characteristics 8
2.2.1 Origin, distribution, and production of sorghum 8
2.2.2 Uses of sorghum 10
2.2.3 Nutritional composition and anti-nutrients in sorghum 11
2.3 Grain amaranth production, uses and chemical composition 13
2.3.1 Origin, distribution, production, and uses of grain amaranth 13
2.3.2 Nutritional composition and anti-nutrient factors of amaranth grain 14
2.4 Origin, distribution, uses and nutrition value of baobab tree fruit 15
2.5. Orange-fleshed sweet potatoes production, uses and chemical characteristics 16
2.5.1 Origin, distribution, and production of orange-fleshed sweet potatoes (OFSP). 16
2.5.2 Uses, nutritional composition and anti-nutrients of OFSP 17
2.6 Composite flours 18
2.6.1 History, shelf-life and nutritional composition of composite flour 18
2.7 Extrusion cooking 19
CHAPTER THREE: NUTRIENT AND ANTI-NUTRIENT COMPOSITION OF EXTRUDED CEREAL FLOURS FORTIFIED WITH GRAIN AMARANTH,BAOBAB AND ORANGE-FLESHED SWEET POTATO POWDER
3.1 Introduction 24
3.2 Materials and methods 26
3.2.1 Raw material acquisition 26
3.2.2 Sample preparation 26
3.2.3 Formulation of the composite flours 26
3.2.4 Analytical methods 28
3.2.5 Statistical analysis 31
3.3 Results 31
3.3.1 Proximate composition of the raw materials 32
3.3.2 Antinutrient content of raw flours 32
3.3.3 Proximate composition of composite flours 36
3.3.4 Micronutrient and antinutrient content of blended flours 41
3.4 Discussion 47
3.4.1 Nutrition composition of raw material 47
3.4.2 Antinutrient content of raw materials 48
3.4.3 Proximate composition of blended flours 48
3.4.4 Micronutrient and antinutrient content of blended flours 49
3.5 Conclusion 51
3.6 Recommendation 52
CHAPTER FOUR: CONSUMER ACCEPTABILITY OF EXTRUDED MAIZE- SORGHUM COMPOSITE FLOURS FORTIFIED WITH GRAIN AMARANTH, BAOBAB AND ORANGE FLESHED SWEET POTATOES
4.1 Introduction 53
4.2 Materials and methods 55
4.2.1 Sample acquisition 55
4.2.2 Sample preparation 56
4.2.3 Formulation of the composite flours 56
4.2.4 Acquisition of commercial composite flours for comparison 57
4.2.5 Porridge preparation 58
4.2.6 Sensory evaluation 58
4.2.7 Data analysis 62
4.3 Results 62
4.3.1 Sensory attributes of blended cereal flours 62
4.3.2 Comparative sensory quality of blended flours to the conventional flours 68
4.3.3 Clustering of sensory qualities of the blended flours 69
4.4 Discussion 72
4.5 Conclusion 74
4.6 Recommendations 74
CHAPTER FIVE: SHELF STABILITY OF EXTRUDED CEREAL FLOURS FORTIFIED WITH LOCALLY AVAILABLE PLANT MATERIALS
5.1 Introduction 76
5.2 Materials and methods 77
5.2.1 Composite flour formulation 77
5.2.2 Sample collection 79
5.2.3 Shelf-life determination 79
5.2.4 Analytical methods 79
5.2.5 Statistical Analysis 80
5.3 Results 81
5.3.1 Model fitting 81
5.3.2 Effect of temperature on the stability of chemical and microbial quality of blended flour 81
5.3.3 Stability of the nutritional composition and microbial quality during storage 83
5.4 Discussion 86
5.6 Recommendations 88
CHAPTER SIX: GENERAL DISCUSSION, CONCLUSION AND RECOMMENDATION
6.1 General Discussion 89
6.2 General conclusion 92
6.3 General recommendations 93
REFERENCES 95
APPENDICES 113
LIST OF TABLES
Table 3.1: Composite flour formulations 27
Table 3.2: Proximate composition of raw flours used in formulating composite flours 33
Table 3.3: Micronutrient composition of raw flours used in formulating blended flours 34
Table 3.4: Effect of fortification of cereal flours with baobab, orange-fleshed sweet potato and amaranth grain powders on their proximate composition 37
Table 3.5: Effect of interaction between formulation and extrusion on the proximate composition of the composite flours 40
Table 3.6: Effect of extrusion and formulation of cereal flours with baobab, orange-fleshed sweet potato and grain amaranth powder on their micronutrient content 43
Table 3.7: Main effect of extrusion and formulation on tannins and phytate contents of composite flour 44
Table 3.8: Correlation between micronutrients and antinutrients in cereal flours 46
Table 4.1: Composite flour formulations 56
Table 4.2:Commercial composites for comparison 57
Table 4.3: Descriptive sensory lexicon developed by the sensory evaluation panel to evaluate the quality of porridge 59
Table 4.4: Main effect of formulation on the sensory attributes of non-extruded composite flours 64
Table 4.5: Effect of the interaction between extrusion and formulation on sensory attributes of blended cereal flours 66
Table 4.6: Comparison of the formulated flour against conventional flour retailed in the market 69
Table 5.3: Effect of temperature on the nutritional composition and microbial quality 82
Table 5.4: Effect of period of storage on nutritional and microbial quality of blended flour 84
Table 5.5: Effect of the interaction between packaging material and period of storage on Moisture, protein and yeast and mould counts 85
LIST OF FIGURES
Figure 3.1: Antinutrient content of raw flours used in formulating blended flours. The error bars indicate the standard error of the mean. 35
Figure 3.2: Effect of extrusion on the proximate composition of fortified cereal flours. 38
Figure 3.3: Effect of the interaction between extrusion and formulation on the phytate content of blended flours. 45
Figure 3.4: Effect of the interaction between extrusion and formulation on the tannin content of blended flours. 46
Figure 4.1: Main effects of extrusion on the sensory scores of blended cereal flours. The error bars represent the standard error of the mean. 65
Figure 4.2: Principal components explaining data variability of the sensory scores for the formulated flour blends 68
Figure 4.3: WSSplot for clustering of the sensory attributes of cereal flour blends 70
Figure 4.4: Clustering of the sensory attributes of blended flours 71
Figure 4.5: Proportion of the sensory scores of blended flours loading into the clusters. 71
Figure 4.6: Principal Component Analysis plot of the sensory attributes of blended flours 72
Figure 5.1: Composite flour development flow diagram 78
Figure 5.1: Stability of fibre content of blended flour at different temperatures of storage 83
LIST OF APPENDICES
Appendix 1: F-values for ANOVA test on the nutritional composition of blended flour 113
Appendix 2: AIC model fitting for ANOVA tests on the nutritional composition of blended flour 114
Appendix 3: Sensory consent form 115
Appendix 4: Sensory evaluation form 116
ABBREVIATIONS AND ACRONYMS
AOAC Association of Official Analytical Chemists
AAS Atomic Absorption Spectrophotometry
ANOVA Analysis of Variance
ASLT Accelerated Shelf Life Testing
CDC Center for Disease Control
CFU Colony Forming Units
FAO Food and Agriculture Organization
FFA Free Fatty Acids
HPLC High-Performance Liquid Chromatography
ISO International Organization for Standardization
LSD Least Significant Difference
OFSP Orange Fleshed Sweet Potatoes
RDA Recommended Daily Allowance
SSA Sub-Saharan Africa
WFP World Food Program
WHO World Health Organization
OPERATIONAL DEFINITIONS
Composite flour: a mixture of flours from cereals, tubers and vegetables with or without wheat.
Extrusion: a high-temperature short-time food processing method in which a moistened food material is plasticized and cooked in a barrel under high pressure and temperature and discharged at atmospheric pressure through a die.
Shelf life: length of time a product is stored without becoming unfit for use.
Sensory evaluation: use of human senses to provide information on how food products are perceived.
ABSTRACT
Micronutrient malnutrition continues to be a problem in developing countries. Food to food fortification which includes composite flour formulation is one of the methods used to reduce the problem. However, the effectiveness of the composite flours is questionable due to the presence of antinutrients in the raw materials used. Therefore, the current study aimed at developing a nutritious, shelf-stable porridge composite flour from maize, sorghum, grain amaranth, baobab and orange-fleshed sweet potatoes.
Nutrient composition data of each ingredient was generated using standard analytical methods and used in the formulation of the composite flours using Nutrisurvey software. To produce various formulations of composite flours with maize and sorghum as the cereal base and grain amaranth, baobab and OFSP as the fortifiers, a completely randomized study design in factorial arrangement with ingredient ratio and extrusion as variables and seven levels was used. Half of each of the formulations were extruded at 160 °C. Nutritional and anti-nutritional profiling followed by sensory evaluation of the composite flours was done. A comparative analysis of acceptability was performed between the best formula and the commercial composites. Stored in kraft paper and plastic containers, the two best formulations, extruded and non-extruded were subjected to real- time shelf-life studies at 20 °C, 30 °C and 40 °C. The data were analyzed using the R Project for StatisticalComputing, R-3.6.3 and inferential statistics done by ANOVA and the means separated using Turkey’s HSD test.
The protein content (8.99 ± 1.03 g/100 g), beta-carotene content (895.90 ± 346.85 µg/100 g), iron content (11.81 ± 9.73 mg/100 g) and zinc content (1.74 ± 0.18 mg/100 g) were improved by fortification of maize-sorghum blends on average. An increase in grain amaranth increased the phytate content. The protein content, beta-carotene content and antinutrients were decreased by 4.7%,40.9% and 35% respectively by extrusion. Consumer acceptability studies showed that the colour, flavour and overall acceptability of the composites (mean 5.7-7.4 on a 9-point hedonic scale) were affected by formulation, with the most acceptable being those containing more sorghum. The comparative study showed that the new formulations had the potential of being accepted. Compared to plastic, the formulated composites stored in Kraft paper were found to degrade faster. The formulations can retain their quality and safety for six months in various ecological zones in both kraft and plastic.
Therefore, locally available ingredients such as grain amaranth, Baobab and OFSP improves the nutrient composition of maize-sorghum composites while processes such as extrusion reduce antinutrients and have a detrimental effect on beta carotene.
Extrusion should be used in baby food. Bioavailability studies on zinc and iron should be conducted to ascertain the effectiveness of extrusion on the reduction of antinutrients. Refortification of extruded flours with beta carotene is recommended.The Ministry of Agriculture, Livestock and Fisheries in collaboration with the Ministry Health can promote these local crops for consumption by the Kenyan population to reduce micronutrient malnutrition.
CHAPTER ONE
INTRODUCTION
1.1 Background
Micro-nutrient malnutrition is one of the major contributors to the global disease burden and affects more than 2 billion people (CDC, 2018). Vitamin A deficiency, iron deficiency and other minerals, such as zinc, are the most common types of micronutrient malnutrition in Africa. Some of the approaches used to help mitigate the issue are fortification and composite flours, but fortified foods are expensive, whereas composite flours are inexpensive alternatives.
Composite flour refers to a mix of cereals such as maize, millet or sorghum, legumes such as soybeans, peas or beans, root tubers such as yams and sweet potatoes and vegetables with varying concentrations of wheat or non-wheat flours (Ekunseitan et al., 2017). FAO introduced the composite flour technology in 1964 intending to replace wheat with other crops such as maize, yam, and cassava (Noorfarahzilah et al., 2014), among others. Owing to their good nutritional composition and ability to boost the functional properties of other products, they are being replaced with other cereal flours (Ndagire et al., 2015). While composite flours are nutritionally rich, the nutrients in some of the raw material used may not be accessible due to anti-nutrients. Extrusion not only decreases antinutrients but also increases iron bioavailability and kills microorganisms. The shelf life of the end product can be impacted by materials that have a high-fat content. Products with higher nutrients than the recommended dietary allowance (RDA) may also be developed if the formulations are not carefully done.
Cereals are the Poaceae family's edible grains and are a staple food and the main source of carbohydrates for most countries. In Kenya, maize, for example, is the staple food (Singh & Kumar, 2016). Flours of sorghum and maize are used in Kenya to make porridge and ugali. Sorghum is a rich source of protein, fibre and the vitamin B complex but also contains anti-nutrients such as tannins. Compared to sorghum and wheat, maize is high in fatty acids and higher quantities of lysine, which makes it a preferable cereal.
Amaranth (Amaranthusspp) is a leafy vegetable that originated in the United States and is one of the earliest domesticated food crops. The grains are rich in the amino acid lysine that is lacking in other grains. Grains are also a good source of protein, fibre, calcium, iron and vitamin C, as well as a good source of potassium, vitamin A, riboflavin and niacin. (Department of Agriculture, 2010).
The Baobab or monkey tree (Adansoniadigitata) is a deciduous tree widely distributed in sub- Saharan Africa (Abdulkarim&Bamalli 2014). Its fruit is rich in vitamin C,pro-vitamin A and minerals such as iron, magnesium, manganese, calcium, zinc, sodium, and phosphorus (Adubiaro et al., 2011). This makes it a good fortifying agent to fix micronutrient malnutrition.
Sweet potatoes are nutritious root tubers. One of the varieties, the orange-fleshed sweet potato (OFSP) is a great source of beta-carotene which is a vitamin-A precursor and polyphenols (Rodrigues et al., 2016) and can therefore be used as a sustainable method of preventing blindness (Honi et al., 2018).
To improve the quantity and quality of cereal nutrients, a great deal of effort has been made. Some of the strategies used to enhance the nutritional quality and organoleptic properties of foods based on cereals are fortification and supplementation. While they are rich in minerals, cereals and legumes have anti-nutritional factors that make them inaccessible. Extrusion is one of the methods of food production that can help minimize the anti-nutrients but also damage the nutrients. It induces protein denaturation, for example, and research is therefore required to determine the conditions of extrusion that can create a healthier product with fewer anti-nutrients.
1.2 Statement of the problem
Micronutrient deficiency is one of the major contributors to the global health burden, with vitamin A, iron and zinc being the most important and 2 billion individuals being affected (CDC, 2018). Composite flours have been used to help alleviate the problem, but because of antinutrients such as tannins and phytates contained in the raw materials used, their effectiveness is questionable. The antinutrients form metal-ion complexes that make them biologically unavailable, especially Zn, Ca and Fe. Some of the techniques traditionally used to minimize the amount of antinutrients in cereals are milling, roasting, germination, fermentation, boiling and soaking, but they affect the nutrient composition of the composite flours. Extrusion is a better choice because, if performed under the correct processing conditions, it not only decreases antinutrients but also increases protein digestibility and iron bioavailability. Therefore, this project seeks to develop a nutritious extruded porridge composite flour that will help reduce micronutrient malnutrition in children below the age of five.
1.3 Justification
If adopted, this project will provide processors and producers with details on the specifications for the extrusion process that produces nutritious composite flours. When adopted by farmers, diversification in the use of maize, sorghum, baobab fruit, grain amaranth and OFSP will be enhanced. Government agencies would also benefit from using this data to make policies to minimize anti-nutrients, such as declaring the extrusion of all baby flours. The project would enhance the awareness of researchers interested in the formulations of composite flour.
1.4. Objectives
1.4.1 Overall Objective
To develop and evaluate the quality of extruded cereal flours fortified with, grain amaranth, baobab andOFSP.
1.4.2 Specific Objectives
i. To determine the nutrient and anti-nutrient composition of cereal flours fortified with Grain Amaranth, Baobab and OFSP
ii. To determine the acceptability of the formulated composite flours as compared to the market composites
iii. To determine the shelf stability of the most acceptable composite flours
1.5 Hypothesis
i. There is no difference in the Nutrient composition and antinutrient composition of extruded and non-extruded cereal flours fortified with Baobab, OFSP and Grain Amaranth.
ii. There is no difference in the acceptability of the formulated composites compared to the market composites.
iii. There is no difference in shelf stability of extruded and non-extruded cereal flours fortified with Baobab, OFSP and Grain Amaranth.
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