EXTRACTION AND CHARACTERIZATION OF WATERMELON SEED OIL

ABSTRACT

The research titled extraction and characterization of watermelon seed oil was carried to investigate the effect that different drying methods, solvents and seed size would have on the quality and quantity of oil from watermelon (Citrilus lanatus) seeds. The watermelon seeds were removed from the pod and washed. The sample was weighed and divided into two equal parts; one part was subjected to sun drying while the other part was subjected to oven drying (at a temperature of 30 oC). Drying by sun as expected was gradual as compared to the oven drying method which was faster and more rapid. The dried seeds (sun-dried or oven-dried) were de-husked, dry-milled into fine crumbs using hand milling machine. The powdered product from the mill was then subjected to oil extraction using hexane and petroleum ether as solvent. Proximate and physico-chemical analysis of water melon seeds were carried out. The results showed that the seeds contained 5.15 ± 0.03 % moisture, 4.90 ± 0.14 % ash, 50.48 ± 0.05 % fat,               32.38 ± 0.02 % protein, 6.10 ± 0.02 % crude fibre and 6.35 ± 0.12 % nitrogen free extract. Physico-chemical characteristics showed that the pale yellow oil had a specific gravity of     0.860 ± 0.003 and a refractive index of 1.471. Saponification value was 184.29 - 187.09 mgKOH/g (for both drying methods). Iodine value was 103.04 – 115.12 mgIodine/g (for both drying methods). Acid value was 10.4 – 12.8 mgKOH/g and free fatty acid was 5.2 – 6.4 mgKOH/g (for both drying methods). The peroxide value was 18.74 meq peroxide/g. The water melon seed can thus be considered a good source of protein with high nutritional value. Many of the physicochemical properties of the seed oil studied compared favourably with other conventional seed oils such as soyabean, cowpea, groundnut etc. The watermelon seed oil therefore has potential for use as domestic and industrial oil.

TABLE OF CONTENTS

Content                                                                                                                                       page

Title Page                                                                                                                                        i                                        

Declaration                                                                                                                                     ii

Certification                                                                                                                                    iii

Acknowledgement                                                                                                                          iv

Abstract                                                                                                                                           v

Table of Content                                                                                                                             vi

List of Tables                                                                                                                                  xi   

List of Figures                                                                                                                                 xi

List of Plates                                                                                                                                   xi

CHAPTER ONE

1.0 INTRODUCTION                                                                                                                    1

1.1 Aims and Objectives                                                                                                                 3

1.2 Scope of the Study                                                                                                                    3

1.3 Problem Statement                                                                                                                    4

1.4 Justification of the Study                                                                                                          4

CHAPTER TWO

2.0 LITERATURE REVIEW                                                                                                         6

2.1 Watermelon Seed Background                                                                                                 6

2.2 Oil                                                                                                                                             7

2.2.1 Fatty Acids                                                                                                                             7

2.2.2 Tocopherols                                                                                                                           7

2.2.3 Oxidative Stability                                                                                                                 8

2.2.4 Refining                                                                                                                                9

2.2.4.1 Degumming                                                                                                                       11

2.2.4.2 Caustic Neutralization                                                                                                       12

2.2.4.3 Bleaching                                                                                                                           12

2.2.4.4 Deodorization Process                                                                                                       13

2.2.5 General Features of Glycerides Structure in Natural Fats                                                    14

2.3 Nutritional Benefits of Watermelon Seed Oil                                                                         15

2.3.1 Application of Watermelon Seed Oil                                                                                   16

2.3.2 Health Benefits of Watermelon                                                                                            18       

2.4 Leaching                                                                                                                                  18

2.4.1 Methods of Extraction                                                                                                          19

2.4.1.1 Supercritical Fluid Extraction                                                                                           19

2.4.1.2 Solvent Extraction                                                                                                             20

2.4.1.3 Mechanical Pressing Extraction                                                                                        21

2.4.2 Factors Influencing the Rate of Extraction                                                                          21

2.4.2.1 Particle Size                                                                                                                      21

2.4.2.2 Solvent                                                                                                                              22

2.4.2.3 Temperature                                                                                                                      22

2.4.2.4 Agitation of Fluid                                                                                                             22

2.4.3 Choice of Solvent                                                                                                                23

2.4.3.1 Selectivity                                                                                                                         23

2.4.3.2 Recoverability                                                                                                                  23

2.4.3.3 Volatility                                                                                                                          23

2.4.3.4 Purity                                                                                                                               23

2.4.3.5 Solubility                                                                                                                         23

2.4.3.6 Inflammability                                                                                                                 24

2.4.3.7 Safety                                                                                                                               24

2.5 Physico-Chemical Properties of Oil                                                                                       24

2.5.1 Acid Value (Free Fatty Acid)                                                                                              24

2.5.2 Saponification Value                                                                                                           25

2.5.3 Iodine Value                                                                                                                        25

2.5.4 Peroxide Value                                                                                                                    26

2.5.5 Refractive Index                                                                                                                  26

2.5.6 Specific Gravity                                                                                                                  27

2.5.7 Viscosity                                                                                                                             27

2.6 Proximate Analysis of Oil Bearing Seeds                                                                             27

2.6.1 Moisture Content                                                                                                                27

2.6.2 Crude Fiber                                                                                                                         28

2.6.3 Ash Content                                                                                                                        29

2.6.4 Nitrogen Free Extract                                                                                                         29

2.6.5 Crude Protein                                                                                                                      30

2.6.6 Oil Content                                                                                                                         30

CHAPTER THREE

3.0 MATERIALS AND METHOD                                                                                             32

3.1 SAMPLE PREPARATION ANALYSIS                                                                              32

3.1.1 Crushing and Grinding                                                                                                       32

3.1.2 Sieving                                                                                                                             32

3.1.3 Drying                                                                                                                              33

3.1.4 Materials and Apparatus                                                                                                  33

3.1.5 Reagents                                                                                                                          34

3.2 Proximate Analysis                                                                                                            34

3.2.1 Oil Content                                                                                                                      34

3.2.2 Moisture Content                                                                                                             35

3.2.3 Crude Fiber                                                                                                                      36

3.2.4 Ash Content                                                                                                                     37

3.2.5 Nitrogen Free Extract                                                                                                      38

3.2.6 Crude Protein                                                                                                                   39

3.3 Physico – Chemical Properties of Watermelon Seed Oil                                                   39

3.3.1 pH                                                                                                                                    39

3.3.2 Refractive Index                                                                                                              40

3.3.3 Viscosity                                                                                                                          40

3.3.4 Specific Gravity                                                                                                               40

3.3.5 Acid Value (Free Fatty Acids)                                                                                         41

3.3.6 Saponification Value                                                                                                        41

3.3.7 Peroxide Value                                                                                                                 42

3.3.8 Ester Value                                                                                                                       43

3.3.9 Iodine Value                                                                                                                     43

 

 

CHAPTER FOUR

4.0 RESULTS AND DISCUSSION                                                                                          45

4.1 Results                                                                                                                                  45

4.2 Discussion of Results                                                                                                           50

CHAPTER FIVE

5.0 Conclusion and Recommendation                                                                                        56

5.1 Conclusion                                                                                                                            56

5.2 Recommendation                                                                                                                  57

REFERENCES                                                                                                                         58

APPENDICES                                                                                                                           64