Extraction of Oil From Watermelon Seed
Chapter One
Aims and Objectives
The aims and objectives of the project are;
- Determine the oil content in the watermelon seed using soxhlet extractor.
- Determine the physico-chemical characteristic properties of the extracted oil.
- Use of normal hexane and petroleum ether as an extractive solvent.
- Effect of two drying methods on the physico-chemical properties of the watermelon seed oil.
- Determine its edibility and effectiveness in soap making.
- Determine the proximate analysis of the seed.
Chapter Two
LITERATURE REVIEW
Watermelon Seed Background
Watermelon seed (citrullus lanatus) oil is also known as Ootanga and Kalahari oil. It is an annual training herb which is grown widely in warm temperature, subtropical regions all over the world. It comes from the diminutive form of citrus and referring to colour and shape of the fruit, and vulgaris meaning common or ordinary fruit. Its English common name, watermelon comes from the flesh of this succulent fruit, which contain over 90 % water. Native of Africa, it was a valuable and portable source of water for desert situations and when natural water supplies were contaminated. It is eaten fresh or raw in this part of the world for its cool and refreshing juice, and the seeds are usually thrown away as waste. The protein content of the seeds varies from 25 -32 % while the oil content varies from 20-50 % (Ige et al., 1984). In some parts of the world, the seeds are eaten as sources of protein and oil, and at times ground into flour, which is incorporated into cereal flour for bread making. Watermelons were first cultivated in Egypt where testaments to their legacy were recorded in hieroglyphics painted on building walls. The fruit was held with such high regards that it was placed in the tombs of many Egyptian kings. It is not surprising that watermelon played an important role in Egypt, and subsequently in countries in the Mediterranean region, since water was often in short supply in these areas, and people could depend upon watermelon for its thirst-quenching properties. Watermelons were brought to China around the 10th century and then to the Western Hemisphere shortly after the discovery of the New World. In Russia, where much of the commercial supplies of watermelons are grown, there is a popular wine made from this fruit. In addition to Russia, the leading commercial growers of watermelon include China, Turkey, Iran and the United States (Ali et al., 2008).
In Nigeria, traditional protein foods such as meat, fish, poultry and dairy products are expensive and therefore the majority of population cannot afford them. In this regard, attention has been shifted to alternative sources of protein particularly among the oil seeds, kernels and less known plant sources. Extraction and characterization of a food source, determine not only average nutrient content, but also help to find alternative uses for such food materials.
Oil
Fatty Acids
The fatty acid (FA) composition determines the physical properties, the stability and the nutritional value of lipids. All lipids of natural origin consist of saturated FA, monoenoic FA, and polyunsaturated fatty acids (PUFA) in various proportions and differ in detailed FA composition. Variations in plant and animal lipid FA composition make it possible to determine the origin of the lipids. FA distribution in triacylglycerol (TAG) as well as in phospholipids affects the physical properties, lipolytic and oxidative stability, and nutritional availability of lipids. In many TAGs, the fatty acids are arranged in a non-random distribution. In plants, monoenoic FA and PUFA are dominant at sn-2 position. In some animal fats the TAG sn-2 position is occupied by palmitic acid (Kolakowska et al., 2003).
Tocopherols
The tocochromoanols comprise a group of chemically related tocopherols and tocotrienols, which are similar in molecular structure and occur in plants, plant oils, nuts, grains, fruits and vegetables. All compounds in the homologues, exhibit antioxidative and vitamin E activity. In all homologues the basic structural unit is a chroman ring system (2-methyl-6-hydroxy-chroman) with an isoprenoid side chain with 16 C-atoms. The homologues differ in the number and distribution of methyl groups in the aromatic ring. Tocopherols differ from tocotrienols because they have a saturated side chain. Tocopherols are antioxidants possessing a “carry through” property; this is defined as the ability of an antioxidant to survive the technological process, mainly the heat treatment of food stuffs, and transfer the stabilizing activity to the final product. Acting as chain-breaking antioxidants, tocopherols react with lipid radicals to convert them into more stable products (Kolakowska et al., 2003).
The major lipid radical formed at normal oxygen pressure is the peroxy radical ROO, which is converted into a hydroxyperoxide by a hydrogen donator. The mode of action of tocopherols as antioxidants is explained by their role in donating hydrogen from their phenolic group to radicals, to stabilize them and to stop the growing formation of hydroperoxides. The resulting tocopheryl semiquinone radical molecule itself, which loses the antioxidative properties, shows different possibilities for further reacting. Two tocopheryl semiquinone molecules can form one molecule of the stable tocopherylquinone and one regenerated molecule of tocopherol. The reaction between the two radicals may also form tocopherol dimers, especially the g – tocopherol-biphenyl-dimer and the g-tocopherol-ether-dimer, which have antioxidative properties. A model study showed that g -tocopherol was superior to a-tocopherol as an antioxidant, because it oxidizes to more stable compounds, which are still effective as antioxidants (Wagner and Elmadfa, 1999).
The tocopherol content of foods is important to protect food lipids against autoxidation and, thereby to increase their storage life and their value as wholesome foods.
Chapter Three
MATERIALS AND METHOD
Sample Preparation Analysis
The watermelon seeds were obtained from station market, a local market in Kaduna, Kaduna State, in the Northern part of Nigeria. The seeds collected were washed and dried for easy removal of the epicarp. The watermelon seeds were then divided into two, one portion of which was subjected to sun-drying while the second was oven-dried. Each sample of 100gm was dry-milled and the oil content was extracted by Soxhlet extraction method before being subjected to physico-chemical analyses. Proximate composition of the seed was also determined.
Crushing and grinding
Crushing is the first step in the process of size reduction. Crushing is sufficient but for chemical processes, grinding to reduce and produce a fine size powder usually follows it. There is no special engine for the grinding of the watermelon seeds but the general melon grinding machine was used for the purpose of this work (Local manual grinding machine).
Chapter Four
RESULTS AND DISCUSSION
Results
The summary of the proximate composition of watermelon (Citrullus lanatus) seed is shown in Figure 4.1 and Table 4.1.The moisture content of the seed is quite low (5.15 %) and falls within the range of moisture contents of similar seeds. The ash content (4.9 %) obtained during proximate analysis is higher than the established value for animal feed. Figure 4.1 presents the composition of watermelon seed from the result of the proximate analysis and also shows clearly that fat, crude protein and nitrogen free extract are highest.
Chapter Five
CONCLUSION AND RECOMMENDATION
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.
Recommendations
Further research on the following subject matters should be carried out on watermelon seed and oil;
- Characterization of seed and seed oil of watermelon and the kinetics of degradation of the oil during heating.
- Physico-chemical and toxicological studies on watermelon seed and oil.
- Tocopherol and sterol contents of watermelon seed oil.
- Comparative studies on nutritional composition of watermelon seed oil varieties.
- Physical properties of watermelon seed as a function of moisture content and variety.
- Extraction performances of polar and non-polar solvents on the physical and chemical indices of watermelon seed oil.
References
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