ABSTRACT
The study was undertaken to determine the physicochemical, nutritional, chemical and sensory properties of yoghurts produced from blends of soybean and mung bean milks. Soybean and mung bean milks were blended at different ratios (100:0, 80:20, 50:50, 20:80 and 0:100) and used to produce yoghurts while 100% cow milk was used to produce the control. Physicochemical, antinutrient, and sensory evaluations were conducted on the yoghurt formulations. The results of the physicochemical properties were in the range of 11.04-14.71 (11.69)% Total solid, 1.105-1.137 (1.069)g/cm3 Specific gravity, 5.80-5.98 (5.53)% pH, 0.61-0.65 (0.75)% Total titratable acid and 9.85-11.23 (10.45)% Brix; proximate composition were in the range of 85.28-88.96 (88.47)% moisture, 1.92-2.04 (1.13)% ash, 0.12-0.22% (0.00) fibre, 0.91-2.00% (2.84)% fat, 3.25-4.31% (5.59)% protein, and 2.57-8.41 (2.95)% carbohydrate; minerals were ranged from 46.76-65.83 (208.28) Ca, 22.40-30.80 (13.60) Mg, 40.64-122.27 (54.47) K, 17.94-43.89 (58.53) Na and 88.93-166.24 (34.67)mg/100g Phosphorus; Vitamins were ranged from 14.50-17.93 (9.84)IU/100g vitamin A, 0.11-0.14 (0.07) thiamine, 0,03-0.04 (0.13) riboflavin, 0.15-0.32 (0.07) niacin and 0.27-2.15 (0.00)mg/100g vitamin C; Phytochemicals were ranged from 0.087-0.173 (0.000)% flavonoids, 0.117-0.153 (0.000) phenols, 0.000-0.073 (0.000) tannins and 0.020-0.107 (0.000)mg/100g alkaloids; while antinutrient contents were in the range of 1.91-2.45 (0.00)mg/g trypsin inhibitor, 0.05-0.11 (0.00)% phytate, 0.02-0.04 (0.00)% saponin and 3.08-5.05 (0.00)mg/g haemagglutinin. The plant-based yoghurts recorded acceptable sensory characteristics, although incorporating mung bean milk at a level above 50% resulted in low sensory quality compared to the control. A blend of at least 80% soybean and 20% mung bean will be ideal to produce organoleptically acceptable plant-based yoghurt with good physicochemical and nutritional properties. The study recommended that further efforts should be made to ensure commercialization of yoghurt based on blends of soybean and mung bean as a cheaper alternative to cow milk yoghurt.
TABLE OF CONTENTS
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of contents vi
List of tables xi
List of figures xii
List of plates xiii
Abstract xiv
CHAPTER 1: INTRODUCTION
1.1 Background of Study 1
1.2 Statement of the Problem 2
1.3 Justification of Study 3
1.4 Objectives of the Study 3
CHAPTER 2: LITERATURE REVIEW
2.1 Overview of Yoghurt 4
2.2 Types of Yoghurt 5
2.2.1 Balkan-Style Yoghurt 5
2.2.2 Greek-Style Yoghurt 6
2.2.3 European –Style Yoghurt 6
2.2.4 French-Style Yoghurt 6
2.2.5 Fruit Yoghurt 7
2.3 Health Benefits of Yoghurt 7
2.4 Problems of Cow Milk Yoghurt and need for Alternatives 8
2.5 Soy Bean 9
2.6 Nutritional Composition of Soybean 10
2.7 Functional Properties of Soybean 10
2.8 Soybean Yoghurt 14
2.9 Mung Bean (Vigna Radiata) 15
2.10 Nutrient Composition and Nutritional Value of Mung Bean 15
2.11 Mung Bean Yoghurt 17
2.12 Nutritional Problems Associated With Legume-Based Yoghurt 17
CHAPTER 3: MATERIALS AND METHODS
3.1 Source of Sample 19
3.2 Sample Preparation 19
3.2.1 Preparation of Soymilk 19
3.2.2 Preparation of Mung Bean Milk 19
3.2.3 Preparation of Cow Milk 20
3.3 Production of Soybean, Mung Bean and Cow Milk Yoghurt 20
3.3.1 Yoghurt Formulation 24
3.4 Chemical Analysis 24
3.4.1 Determination of Phytonutrients 24
3.4.1.1 Determination of Alkaloid 24
3.4.1.2 Determination of Flavonoids 25
3.4.2 Determination of Antinutrients 25
3.4.2.1 Determination of Determination of Haemagglutinin 25
3.4.2.2 Determination of Trypsin Inhibitor 26
3.4.2.3 Determination of Saponin 27
3.5 Physicochemical Analysis 28
3.5.1 Determination of pH And Titratable Acidity 28
3.5.2 Determination of Total Solids and Brix Value 28
3.6 Proximate Analysis 28
3.6.1 Determination of Moisture Content 28
3.6.2 Determination of Ash Content 29
3.6.3 Determination of Crude Fibre 29
3.6.4 Determination of Crude Fat 30
3.6.5 Determination of Crude Protein 30
3.6.6 Determination of Carbohydrate 31
3.7 Mineral and Vitamin Analysis 31
3.8 Sensory Evaluation 31
3.9 Experimental Design / Statistical Analysis 32
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Proximate Composition of the Yoghurts 33
4.1.1 Moisture 33
4.1.2 Protein 33
4.1.3 Fat 35
4.1.4 Fibre 35
4.1.5 Ash 35
4.1.6 Carbohydrate 36
4.2 Physicochemical Properties of the Yoghurt Samples 36
4.2.1 Total Solid (T.S) 36
4.2.2 Specific Gravity (S.G) 38
4.2.3 pH 38
4.2.4 Total Titratable Acidity (TTA) 38
4.2.5 Brix 39
4.3 Mineral Contents of the Yoghurt 39
4.3.1 Calcium 39
4.3.2 Magnesium 41
4.3.3 Potassium 41
4.3.4 Sodium 41
4.3.5 Phosphorus 42
4.4 Vitamin Composition of the Yoghurt Samples 42
4.4.1 Vitamin A 42
4.4.2 Thiamine 44
4.4.3 Riboflavin 44
4.4.4 Niacin 44
4.4.5 Vitamin C 45
4.5 Phytochemical Composition of the Yoghurt 45
4.5.1 Flavonoid 45
4.5.2 Phenols 47
4.5.3 Tannins 47
4.5.4 Alkaloids 47
4.6 Antinutrient Composition of the Yoghurt 48
4.6.1 Trypsin Inhibitor 48
4.6.2 Phytate 48
4.6.3 Saponin 50
4.6.4 Haemagglutinin 50
4.7 Sensory Properties of the Yoghurt 50
4.7.1 Appearance 50
4.7.2 Aroma 52
4.7.3 Taste 52
4.7.4 Mouth Feel 52
4.7.5 Aftertaste 52
4.7.6 Consistency 53
4.7.7 General Acceptability 53
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1 Conclusion 55
5.2 Recommendation 55
REFERENCES
APPENDICES
LIST OF TABLES
Table 2.1: Chemical And Nutritional Constituents Of Mung Bean 16
Table 3.1: Yoghurt Formulations 24
Table 4.1: Proximate Composition Of The Yoghurts (%) 34
Table 4.2: Physicochemical Properties Of The Yoghurt 37
Table 4.3: Mineral Composition Of The Yoghurt (Mg/100g) 40
Table 4.4: Vitamin Contents Of The Yoghurt (Mg/100g) 43
Table 4.5: Phytochemical Composition Of The Yoghurt (Mg/100g) 46
Table 4.6: Antinutrient Composition Of The Yoghurt 49
Table 4.7: Sensory Properties Of The Yoghurt 51
LIST OF FIGURES
Figure 3.1: Flow chart for production of soy milk 21
Figure 3.2: Flow chart for production of mung bean milk 22
Figure 3.3: Flow chart for production of cow milk, soy milk and mung bean yoghurt 23
LIST OF PLATES
Plate 1: 100% Soy Bean Yoghurt 54
Plate 2: 80% Soy bean 20% Mung Bean Yoghurt 54
Plate 3: 50% Soy Bean 50% Mung Bean Yoghurt 54
Plate 4: 20% Soy Bean 80% Mung Bean Yoghurt 54
Plate 5: 100% Mung Bean Yoghurt 54
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF STUDY
In recent years consumers are increasingly interested in incorporating healthy foods into their diet and in many circumstances are willing to pay more for food with functional properties. Fermented dairy products such as yoghurt, also categorized in functional foods group, are considered to have functional properties because of its enhanced nutritional values and the presence of probiotics (Reid, 2006). Yoghurt is a cultured and fermented food product obtained through controlled fermentation of milk (anaerobic fermentation) by means of culture of lactic acid bacteria to produce a characteristic mild clean lactic flavour and typical aroma (Olatidoye, et al., 2017). Yoghurts come in a variety of textures, fat contents and flavours; can be consumed as a snack or part of a meal, as a sweet or savoury food; and are available all year-round. This versatility, together with their acceptance as a healthy and nutritious food, has led to their widespread popularity across all population subgroups (McKinley, 2005).
Conventionally, yoghurt is produced from cow milk and starter culture containing Lactobacillus bulgaricus and Streptococcus thermophillus. Although cow milk produces good quality yoghurt and is an exceptionally good source of protein because of its excellent assortment of essential amino acid, it is expensive due to rising cost of cow milk (Amanze, 2011; Olatidoye, et al., 2017). To meet the protein demands in developing countries, where animal protein is also grossly inadequate and relatively expensive, research effort is geared towards finding alternative sources of protein from legume seeds (Osundahunsi, et al., 2007).
Soymilk is produced from the seed of the leguminous plant, Glycine max. Research has shown that soymilk has beneficial effects on health which include: absence of cholesterol; low sugar; high isoflavone content; high quality protein, etc. In addition, soymilk yoghurt improves bone health, reduces menopausal symptoms and risk of heart disease and certain cancers (Amanze, 2011).The replacement of cow’s milk with soy milk in the production of yoghurt and other milk products is well documented (Nande, et al., 2008; Ghosh, et al., 2013; Amanze, 2014).
In addition to soy milk, researchers are exploring the possibilities of adding other grain legumes in yoghurt manufacture. Mung bean belongs to pulse group. Pulses have high protein content (18-32%), balanced nutritional composition including appreciable amounts of dietary fiber (approximately 25%) and low fat content (2-5%) (Priyadarshani and Muthumuniarachchi, 2018). The enrichment of yogurt with mung bean to enhance the nutritional and dietary quality of the product has been recommended (Priyadarshani and Muthumuniarachchi, 2018).
1.2 STATEMENT OF THE PROBLEM
The rising emergence of lactose intolerance, milk allergies, environmental concerns, and problems due to diets rich in cholesterol and high cost of animal protein are leading toward a growing demand for dairy alternatives. Plant milk is often presented as a healthy, sustainable, and animal-welfare-friendly alternative. However, the ‘beany’ flavour as well presence as presence of anti nutritional factors common to legumes may limit the acceptability of plant-based yoghurt. There is therefore need to evaluate and compare the safety and level of acceptability of soybean and mung bean yoghurts as alternatives to cow milk yoghurt.
1.3 JUSTIFICATION OF STUDY
Research efforts are currently geared towards finding alternatives to cow milk products including yoghurt. Legumes hold the potential for replacing the more expensive and scare cow milk in yoghurt production. Thus, this study will help to determine the possibility of replacing cow milk with cheaper plant alternatives for yoghurt production.
1.4 OBJECTIVES OF THE STUDY
The main objective of this study was to evaluate and compare the chemical, physicochemical and sensory properties of soybean and mung bean yoghurt.
The specific objectives of this study were to:
i. produce yoghurt using soybean and mung bean
ii. evaluate the proximate composition of the yoghurts
iii. evaluate the mineral and vitamin contents of the yoghurts
iv. evaluate the phytochemical contents of the yoghurts
v. evaluate the anti nutrient composition of the yoghurts
vi. evaluate the physicochemical properties of the yoghurts
vii. evaluate the sensory properties of the yoghurts
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