ABSTRACT
This study was carried out to determine the proximate, vitamins, mineral, anti-nutrients and sensory properties of three varieties of garden egg stews (S.macrocarpon, S.aethiopicum-oval and S.aethiopicum-round). It was carried out using an experimental design. The stews were produced from three varieties of garden eggs and analysed to obtain their chemical and sensory properties. The results obtained were subjected to statistical analysis of variance (ANOVA) and means were separated using Duncan multiple range test and judged at 5% significant confidence level (p>0.05). The results showed that the moisture content of the stews were high ranging from 61.02% to 8.45%. Sample M200 had the highest values for protein (6.26%). There were significant differences in the crude fibre, ash, carbohydrates and energy content of the stews. The calcium content was higher than other elements ranging from 10.63 to 61.05mg/100g while, the lowest of the mineral is zinc. Sample A201 had the highest value in almost all the minerals analyzed while, G202 had the lowest values. The vitamin contents of the stews revealed high amounts of beta carotene ranging from 8.75µg/100g in sample G202 to 37.7µg/100g in sample M200. There were also significant levels of thiamine, riboflavin and niacin (0.12-0.4, 0.11-0.20 and 0.30-0.33mg/100g respectively). Vitamin E had the lowest value (0.03-0.07mg/100g). Sample M200 had the highest value for thiamine (0.41mg/100g) while sample G202 had the lowest value (0.12g/100g). Sample A201 had the highest value for niacin (0.48g/100g) while sample G202 had the lowest value (0.30mg/100g). There were significant differences in the vitamin contents of all the stew samples (P>0.05). The anti-nutrients screening revealed that the stews contained safe levels of tannins, saponins, phytates, alkaloids and flavonoids. The garden egg stews contains appreciable amounts of dietary fibre. The result of this study showed that garden eggs had appreciable amounts of bioactive substances and nutritive components which would justify its wide use as a stew condiment.
TABLE OF CONTENTS
Title Page i
Certification ii
Dedication iii
Acknowledgments iv
Table of Content v
List of Tables x
List of Figures xi
Abstract xii
CHAPTER 1
INTRODUCTION
1.0 Background of the study 1
1.1 Statement of problem 3
1.2 Objective of the study 4
1.2.1 General objective of the study 4
1.2.2 Specific objectives of the study 4
1.3 Significance of the study 5
CHAPTER 2
LITERATURE REVIEW
2.1 Brief history of egg plants 6
2.2 General development of eggplant 7
2.3 General characteristics of garden egg 10
2.4 Nutrient composition of garden egg 10
2.4.1 Anti-nutritional factors in egg plant 12
2.4.1.1 Glycoalkaloids 12
2.4.1.2 Tannin 14
2.4.2 Dietary fibre 14
2.5 Health benefits of dietary fibre 14
2.6 Health benefits of eggplants 15
2.7 Uses of eggplant 18
CHAPTER 3
MATERIALS AND METHODS
3.1 Experimental design 22
3.2 Sample collection 22
3.3 Development of stew recipe and methods 22
3.3.1 Garden eggs sample preparation 22
3.3.2 Garden egg stew recipe 24
3.3.3 Procedure for garden egg stew preparation 25
3.3.4 Tomatoes stew recipe 26
3.3.5 Preparation of tomato stew 26
3.4 Chemical analysis 27
3.4.1 Proximate composition 27
3.4.1.1 Determination of moisture content 27
3.4.1.2 Ash content 28
3.4.1.3 Crude fibre content 29
3.4.1.4 Protein content 29
3.4.1.5 Fat content 30
3.4.1.6 Carbohydrate content 31
3.4.1.7 Energy content 31
3.4.2 Vitamins analysis 32
3.4.2.1 Determination of vitamin B1 (Thiamine) 32
3.4.2.2 Determination of vitamin B2 (Riboflavin) 33
3.4.2.3 Determination of vitamin E 34
3.4.2.4 Beta-carotene content determination 34
3.3.3 Mineral content 35
3.4.2.1 Determination of calcium 35
3.4.2.2 Determination of iron content 36
3.4.3.3 Determination of sodium and potassium 36
3.4.3.4 Determination of zinc 37
3.4.3.4 Determination of phosphorus 38
3.4.4 Antinutrients 39
3.4.4.1 Determination of tannin 39
3.4.4.2 Flavonoid determination 40
3.4.4.3 Determination of alkaloid 41
3.4.4.4 Determination of saponin 41
3.4.4.5 Determination of phytate 42
3.4.5 Dietary fibre 43
3.5 Sensory evaluation 44
3.6 Statistical analysis 45
CHAPTER 4
RESULTS AND DISCUSSION
4.1 Proximate composition of the stew samples 46
4.2 Mineral composition of the stew samples 49
4.3 Vitamin composition of the stew samples 52
4.4 Anti-nutrient composition of the stew samples 54
4.5 Dietary fibre composition of the stew samples 57
4.6 Sensory evaluation of the stew samples 59
CHAPTER 5
CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 62
5.2 Recommendations 62
References 64
Appendix i
Appendix ii
LIST OF TABLES
Table 3.1 Recipe for garden egg stew 24
Table 3.2 Recipe for tomato stew 26
Table 4.1 Proximate composition of the stew samples 46
Table 4.2 Mineral content of the stew samples 49
Table 4.3 Vitamin composition of the stew samples 52
Table 4.4 Anti-nutrient composition 54
Table 4.5 Dietary fibre composition 57
Table 4.6 Sensory scores of the stew samples 59
LIST OF FIGURES
Figure 3.1 Flowchart for preparation of blended garden egg 23
CHAPTER 1
INTRODUCTION
1.0 Background of the study
Solanum, a widespread plant genus of the family Solanaceae, has over 100 species which are indigenous to Africa and several of these have been developed as vegetables (Ojimelukwe, 2019). Solanum aethiopicum fruits showed significant amounts in its chemical constituents and the fruit contains good amounts of phytochemicals and nutritive components including vitamins and minerals (Eze et al., 2014).
Garden egg (Solanum gilo) is one of the most important members of the genus solanum cultivated in West Africa. Most people prefer its fruits to those of other aubergine types because the fruits of the former are less susceptible to blacken on peel. The eggplants form part of the traditional sub-Saharan African culture. The fruits, said to represent blessings and fruitfulness, are offered as a token of goodwill during visits, marriages and other social events. They are eaten raw and also when boiled or fried as ingredient of stews, soups and vegetable sauces (Ayodele, 2018).
Wide variation exist within the vegetative and fruit characters both within and between the African eggplant species including variations in characters like diameter of corolla, petiole length, leaf blade width, plant branching, fruit shape, and fruit color (Osei et al., 2010). Local names for Solanum aethiopicum in Nigeria include: garden egg (Hausa: Dauta; Igbo: afufa or añara; Yoruba: Igbagba). It is a highly valued constituent of the Nigerian foods and indigenous medicines; it is frequently consumed by both rural and urban families. The fruits are offered as a welcome gesture during visits, marriages, funerals and other social events. They are eaten raw and may also be boiled or fried and used as ingredient of stews, soups and vegetable sauces (Ossamulu et al., 2014).
Nutritionally, the plant contains various nutrients and phytonutrients such as nasunin and chlorogenic acids, which are good antioxidants. It is also a good source of fibre and is low in calories, fat and sugar. Eggplant is also high in bioflavonoids, anthocyanin (Nimenobo et al., 2017). Ossamulu et al., (2014) reported that eggplant fruits generally have high moisture content, high concentrations of saponins, alkaloids and tannins.
Sensory evaluation of vegetables brings about very valuable information on their quality characteristics, level of acceptability with a consequence on adoption potential and sensory traits of vegetables are the main factors that determine consumer satisfaction (Eze et al., 2012).
Garden eggs are used in many native cuisines of the world. Whether you choose to grill it, roast it, sauté it, or blend it into smooth dips, you will still have a better chance to enjoy them because the recipes are versatile. Eggplant stew or sauce is another simple delicious way to enjoy these vegetables; it is a good substitute to fried tomato stew. It can be eaten with boiled yam, boiled sweet potatoes, boiled rice or boiled plantains (Etim, 2017).The proximate, vitamins, mineral anti-nutrients and sensory evaluation of three varieties of eggplant stews was evaluated in this study.
1.1 Statement of the Problem
Micronutrient deficiencies form an important global health issue with malnutrition affecting key development outcomes including poor physical and mental development in children, vulnerability or exacerbation of disease, mental retardation, blindness and general losses in productivity and potentials (Ritchie et al., 2017).
Micronutrient deficiency is one of the major problems encountered in Nigeria with alarming prevalence of micronutrient deficiencies that has persisted over the decades (Anjorin et al., 2019).
Chronic non communicable diseases is a global health problem and is linked in part to dietary factors and low fruits and vegetable intake has been associated with higher rates of cardiovascular disease (WHO, 2013). Notable among these chronic diseases are cardiovascular diseases, stroke, hypertension, diabetes and some type of cancers. It has become a global health issue which threatens Sub-Saharan Africa including Nigeria. A study revealed a high prevalence of non-communicable diseases risk factors among Nigerian civil servants and that overall inadequate fruits and vegetable intake as well as physical inactivity were the commonest risk factors (NCBI, 2018).
Fruits and vegetable provides dietary fibers vital for the optimal functioning of the gastrointestinal tract (Slavin, 2008). Fruits and vegetable intake is associated with reduced risk of cardiovascular diseases which supports public health recommendations to increase fruit and vegetable intake for the prevention of cardiovascular diseases, cancer and premature mortality (Dagfinn et al., 2017).
The above problems motivated the researcher to undertake the study on production of stews from different varieties of garden egg as well as determine their nutrient composition and their contributions especially in the fight to reduce micronutrient deficiencies and chronic non Communicable diseases.
1.2 Objectives of the study
General objective:
To determine the chemical composition and sensory properties of stews made from three varieties of garden egg.
Specific objectives
The specific objectives were to:
1. Prepare stews from three varieties of garden egg.
2. Determine the proximate composition of the stews.
3. Determine the vitamins, minerals, and anti-nutrients composition of the stews.
4. Assess the sensory attributes of the garden egg stews.
1.3 Significance of the study
This study will provide information on the chemical composition of stews made from different varieties of garden egg which will motivate people to increase the consumption of garden egg and invariably increasing cultivation of garden egg.
The result of this work will be relevant to nutritionists and dietitians in educating the public on the importance of consuming garden egg and its use in the management of diet related diseases especially chronic diseases.
Families with both low and high income will also benefit because they can grow it in their farms and complement it with other foods, prepare it into stew to provide variety in family menus.
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