Extraction Of Oil From Watermelon Seed

Extraction Of Oil From Watermelon Seed

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
• Declaration
• Certification
• Acknowledgement
• Abstract
• Table of Content
• List of Tables
• List of Figures
• List of Plates

Chapter One

1.0 Introduction

• 1.1 Aims and Objectives
• 1.2 Scope of the Study
• 1.3 Problem Statement
• 1.4 Justification of the Study

Chapter Two

2.0 Literature Review

• 2.1 Watermelon Seed Background
• 2.2 Oil
• 2.2.1 Fatty Acids
• 2.2.2 Tocopherols
• 2.2.3 Oxidative Stability
• 2.2.4 Refining
• 2.2.4.1 Degumming
• 2.2.4.2 Caustic Neutralization
• 2.2.4.3 Bleaching
• 2.2.4.4 Deodorization Process
• 2.2.5 General Features of Glycerides Structure in Natural Fats
• 2.3 Nutritional Benefits of Watermelon Seed Oil
• 2.3.1 Application of Watermelon Seed Oil
• 2.3.2 Health Benefits of Watermelon
• 2.4 Leaching
• 2.4.1 Methods of Extraction
• 2.4.1.1 Supercritical Fluid Extraction
• 2.4.1.2 Solvent Extraction
• 2.4.1.3 Mechanical Pressing Extraction
• 2.4.2 Factors Influencing the Rate of Extraction
• 2.4.2.1 Particle Size
• 2.4.2.2 Solvent
• 2.4.2.3 Temperature
• 2.4.2.4 Agitation of Fluid
• 2.4.3 Choice of Solvent
• 2.4.3.1 Selectivity
• 2.4.3.2 Recoverability
• 2.4.3.3 Volatility
• 2.4.3.4 Purity
• 2.4.3.5 Solubility
• 2.4.3.6 Inflammability
• 2.4.3.7 Safety
• 2.5 Physico-Chemical Properties of Oil
• 2.5.1 Acid Value (Free Fatty Acid)
• 2.5.2 Saponification Value
• 2.5.3 Iodine Value
• 2.5.4 Peroxide Value
• 2.5.5 Refractive Index
• 2.5.6 Specific Gravity
• 2.5.7 Viscosity
• 2.6 Proximate Analysis of Oil Bearing Seeds
• 2.6.1 Moisture Content
• 2.6.2 Crude Fiber
• 2.6.3 Ash Content
• 2.6.4 Nitrogen Free Extract
• 2.6.5 Crude Protein
• 2.6.6 Oil Content

Chapter Three

3.0 Materials and Method

• 3.1 Sample Preparation Analysis
• 3.1.1 Crushing and Grinding
• 3.1.2 Sieving
• 3.1.3 Drying
• 3.1.4 Materials and Apparatus
• 3.1.5 Reagents
• 3.2 Proximate Analysis
• 3.2.1 Oil Content
• 3.2.2 Moisture Content
• 3.2.3 Crude Fiber
• 3.2.4 Ash Content
• 3.2.5 Nitrogen Free Extract
• 3.2.6 Crude Protein
• 3.3 Physico – Chemical Properties of Watermelon Seed Oil
• 3.3.1 pH
• 3.3.2 Refractive Index
• 3.3.3 Viscosity
• 3.3.4 Specific Gravity
• 3.3.5 Acid Value (Free Fatty Acids)
• 3.3.6 Saponification Value
• 3.3.7 Peroxide Value
• 3.3.8 Ester Value
• 3.3.9 Iodine Value

Chapter Four

4.0 Results and Discussion

• 4.1 Results
• 4.2 Discussion of Results

Chapter Five

5.0 Conclusion and Recommendation

• 5.1 Conclusion
• 5.2 Recommendation
• References
• Appendices

Chapter One

1.0 Introduction

The edible fruit of watermelon (Citrullus lanatus) belongs to the family Cubitaceae. The fruit contains many obovate, smooth compressed seeds thickened at the margin and of a black or yellowish white colour. Watermelon plays a very important role in Africa as it is used to quench thirst when there is shortage of water. The seed of watermelon (Citrullus lanatus) can be bruised and rubbed up with water to form an emulsion, which can be used to cure catarrhal infections, disorders of the bowels, urinary passage and fever. It is also being used as worm expeller, in recent years it has been used to expel tape worm (Abiodun and Adeleke, 2010). In Nigeria, the watermelon seed is often discarded after the juicy part has been eaten. The seed constitutes a public nuisance because the sellers of watermelon do not dispose of these in a hygienic manner. Therefore, this project work when successfully completed will convert waste into wealth. From previous studies on watermelon seed oil, it is light penetrating and rich in essential fatty acids (Abiodun and Adeleke, 2010). As a result of importance of drying techniques, this research was designed to observe the effect of two drying methods on the physico-chemical properties of the seed oil and also to determine its edibility and effectiveness in soap making. In Africa, Watermelon seeds have been prized for the highly nutritive oil that they contain. Traditionally, the seeds are removed from the rind and then allowed to dry outside in the sun. Once dried, the seeds are then pressed to extract the beneficial oil. Natural Sourcing provides the most superior watermelon seed oil available. It is carefully processed and packaged to maintain the purity, freshness and beneficial properties of this exceptional watermelon seed oil.

The fatty acid profile of edible oils plays an important role in their stability and nutritional value. Monounsaturated (18:1) and polyunsaturated (18:2) fatty acids have been found to be effective replacements for saturates as part of cholesterol-lowering diets (Mattson and Grundy, 1985). However, it is also known that the oils with substantial amounts of unsaturation, particularly 18:2 fatty acids, are susceptible to oxidation and may produce products that contribute to arteriosclerosis and carcinogenesis. Some studies with experimental animals indicate that excessive amounts of linoleic acid promote carcinogenesis (Kubow, 1990).Watermelon seed oil, rich in linoleic acid (~64.5 %), is used for frying and cooking in some African and Middle Eastern American countries owning to its unique flavour (Akoh and Nwosu, 1992). Much research has been published on the oxidative stability of some vegetable or fruit oils, but a little has been reported on the stability of watermelon seed oil. The modification of watermelon seed oil fatty acid composition by incorporation of oleic acid (18:1) has been explored (Charment et al., 1997). The modified watermelon seed oil was produced with the better balance of monounsaturated (18:1) and essential Fatty acids (18:2), and also improved the seed oil oxidative stability and nutritional value (Charment et al., 1998).The watermelon family Cucurbitaceae is the most popular fruit in Serbia, with a traditional name ″lubenica″.

Unfortunately, there is no information of domestic application or medicinal values of this seed oil for cooking and or frying as useful source of oil with good nutritional value. Thus, watermelon seed oil composition (physical and chemical) shall be evaluated in this present study, which has not been previously investigated. The data generated in the work may help in the future selection of watermelon seed oil for use in human diet.

The light texture, moisturizing capabilities and stable shelf life of watermelon seed oil makes it a highly suitable emollient in natural baby care formulations and light body emulsions. Unlike mineral oil that is a common ingredient in commercial skin projects, watermelon seed oil does not clog pores or prevent the body from natural elimination of toxins through the skin. The rich composition of essential fatty acid contained in watermelon seed oil nourishes and restores elasticity to the skin (Akoh and Nwosu, 1992). It may be recommended for use in skin care formulations for all skin types including dry, oily and maturing skin. Watermelon seed oil may also be a perfect choice for inclusion in hair care formulations as it is non greasy yet highly moisturizing. Grinding the dry seed, flaking or rolling of the seeds to carry out extraction of oil, this is then subjected to mechanical processing to liberate the oil or the use of chemical solvent.

1.1 Aims and Objectives

The aims and objectives of the project are;

1. Determine the oil content in the watermelon seed using soxhlet extractor.
2. Determine the physico-chemical characteristic properties of the extracted oil.
3. Use of normal hexane and petroleum ether as an extractive solvent.
4. Effect of two drying methods on the physico-chemical properties of the watermelon seed oil.
5. Determine its edibility and effectiveness in soap making.
6. Determine the proximate analysis of the seed.

1.2 Scopes

1. Collection of the watermelon seeds from road side hawkers.
2. Drying and removal from the shell.
3. Drying proper (oven drying and sun drying).
4. Cleaning of the seed.
5. Weighing of the watermelon seed.
6. Grinding of the seed.
7. Proximate analysis of the seed.
8. Sieving to obtain particle sizes of varying dimensions.
9. Extraction using soxhlet method, petroleum ether and hexane as solvent.
10. Characterization of the oil (physical and chemical).

1.3 Problem Statement

1. In Nigeria, the watermelon seed is often discarded after the juicy part has been eaten. The seed constitutes a public nuisance because the sellers of watermelon do not dispose of these in a hygienic way. Therefore, this project work when completed will successfully convert waste to wealth which is a good form of waste management.
2. Investigation indicates that a cholesterol rich diet causes abnormally high levels of cholesterol and the related fats and lipids in the blood. Evidence strongly indicates that people with such high levels are more likely to develop atherosclerosis and heart attacks than those with lower levels.

The question that arises therefore is;

How can one lower the cholesterol level in the blood particularly when diary products and meat fats contain cholesterol?

1.4 Justification of the Study

Nutrients in watermelon seeds are able to ward off cancer, improve and or prevent cardiovascular disease, hypertension, and reduce levels of bad cholesterol. The oil obtained from the seed is a good source of healthy fat high in unsaturated fat better than low-fat foods, because of increasing HDL (good cholesterol) and lower LDL (bad cholesterol) (Mattson and Grundy, 1985).

Chapter Five

5.0 Conclusion and Recommendation

5.1 Conclusion

Water melon seeds contain high levels of oil and protein with low levels of moisture and ash content, thus making it a potential source of edible oil. Many of the physico-chemical properties of the seed oils studied compared favourably well with other conventional seed oils such as palm kernel oil, groundnut oil, and soybean oil. Its colour and odour are pleasant. The seed oil therefore has potential for use as domestic and industrial oil. The watermelon seed oil is of high economic value in different ways. The result of this study showed that watermelon seed is nutritionally richer than some other nuts and seeds. The high protein content in the watermelon seed oil showed its potential to supply adequate amount of amino acids for children and adults. The physicochemical properties of the watermelon seed oil indicated that it is non drying, edible (when refined) and unsuitable for soap production because of the low saponification value when compared to other seed oils (coconut, palm kernel seed oils) of higher saponification value. The results of this work and of other works may offer scientific basis for the use of the seeds and the oil to complement current research in the area of alternative sources of industrial vegetable oils.

5.2 Recommendations

Further research on the following subject matters should be carried out on watermelon seed and oil;

1. Characterization of seed and seed oil of watermelon and the kinetics of degradation of the oil during heating.
2. Physico-chemical and toxicological studies on watermelon seed and oil.
3. Tocopherol and sterol contents of watermelon seed oil.
4. Comparative studies on nutritional composition of watermelon seed oil varieties.
5. Physical properties of watermelon seed as a function of moisture content and variety.
6. Extraction performances of polar and non-polar solvents on the physical and chemical indices of watermelon seed oil.

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