In the major world, one major source of protein and vegetable oil is from oil seeds /fruits (Williams M. A. 1996). Oil constitutes a well defined class of naturally occurring substance. It is greasy, being soluble in organic solvents but insoluble in polar solvents such as water. Oil is a liquid at room temperature. Commercially, oil as well as fats is sourced from certain plant groups mostly seeds and nuts and some parts of animal within which they occur in relatively large quantity in an easily available form (McGraw-Hill, 1997). The existence of oil in certain plants has been known for century of years (Ogbu 2005).Oil can be grouped into edible and non-edible oil depending on the amount of unsaponified matters and impurities contained therein. Edible oil extracted from African pear, bread fruits, cashew nut, peanut etc. are examples of vegetable oil which are naturally occurring esters of higher fatty acids and glycerol, and are predominantly triglycerides with traces of mono and diglycerides, sterples, anti-oxidants, vitamins, saturated and unsaturated free fatty acids and other minor constituents. They are widely distributed in nature and were first consumed as food. Later, oils were discovered to be used as renewable raw materials for variety of non-food production. For instance; soaps, creams, disinfectants, paints, enamels, inks etc.
Due to the oil boom in the early 70‟s, agriculture was abandoned for petroleum and its product, but recently, things are taking a new turn in Nigeria over dependence on petroleum for virtually everything has not really helped matters. The economic situation in the country is bad and the general standard of living is getting poorer with each passing day, Hence, the need for a restructure of the economic system with an agricultural bias.
Most agriculture products such as these oils extracted from local seeds and nut, if properly monitored and harvested can be very useful for us down here and even exported for foreign exchange, hence the need for this project which deals on the extraction and analysis of African pear oil.
Extraction of oil from various vegetable resources is of ancient origin. In fact, the natives from different tropical regions of the globe have long been extracting oil from numerous oil-bearing plants. Humans, since the ancient times have known how to extract fats and oil from their natural resources. Historically, oils had been extracted by wrapping nuts in clothes and then using devices operated by stones and levers to exert pressure on them. But now, an improved form of mechanical device, which allowed considerably more pressure to be exerted, is now in use in form of hydraulic operated ram. This type of press is developed into a motorized hydraulic pump system that pressed the nut bag and then released a pressed cake. The next improvement in extracting oil is the screw press or expeller which is been driven by electric motor.Because most press or expeller processes leads to over-heating of the meal and leave too- much of the high value oil in cakes, better methods of extracting the oil with solvent was developed. Bush pear was processed by solvent methods alone in this project. This process can be accomplished by a variety of ways but as might be expected, its efficiency depends to a great extent on attaining intimate contact between the liquid solvent and the solid containing the solute. The type of solvent available for this process include n-hexane, petroleum ether, benzene, n-heptanes, acetone etc.
1.1 HISTORICAL BACKGROUND OF THE STUDY
The generic name “Dacryodes” was derived from the Greek word “Dakruon” meaning [tear] referring to resin droplets on the bank surface of its member while “Edulis” means edible emphasizing the importance of nutrients fruits in the plants cultivation .The plant belongs to the family Burseraceae whose members are characterized by an ovary of 2to 5 cells, prominent as inducts in the bark, wood, and intrasteminal disk (Chunduff, 1984). The genus Dacryodes consist of about 10 species (Verheji, 2002). However (Rehn, 1984) indicated 80 species to encompass sub species of varieties, form and cultivars. Two varieties are recognized; Var-parvicarpa and Var-edulis whose conical fruit is smaller with the pulp. Var-edulis exhibit verticulate or sub-verticulate branching while the branching is slender and opposite or bifurcate in var-parvicarpa (Okafor et.al 1983).
Dacryodesedulis is an indigenous fruit in the Gulf of Guinea and central African countries(Troupin, 1950), but due to the popularity of the nutritious fruit for consumption, the plant is widely cultivated, extend its area of distribution to Sierra-Leone, Uganda, Angola, Zimbabwe and Nigeria. It rarely grows wild, thus the natural area of distribution is obscure (verheji,2002). Lam gave four synonyms viz to the Dacryodesedulis :CarnaruimedulieHook.f, CarnaruimsaphuEngl, Pachylobusedulis (G.don) Hook. F. and PachylobussaphuEngl (Burkill ,1985,National research council,1996).
However, these synonyms have long been considered as the most unambiguous synonyms (Boutelje,1980).The common names are in English, African pear, African pear tree, Bush butter, Bush butter tree, Bush fruit tree, Eben tree, Native pear (Kapseu and Tchiegang, 1996) and in French, Safoutier (Burkill, 1985). The oil of fruits of DacryodesEdulis is a rich source of amino acids and triglycerides. The fatty acid composition of fruit pulp oil of two cultivars of bush pear [cultivar1 and cultivar2] grown in Nigeria were determined. The oil is found in the pulp which is made up of 48% of oil and a plantation can produce 7.8 tons of oil per hectare. It is also rich in vitamins and a rich source of amino acids triglycerides (Derbyshire.et al 1976).
Bush pear oil is one of the most important rated versatile vegetable oil. This is due to its uses in various spheres of life, most especially as a very healthy food ingredient.
1.2 AIMS AND OBJECTIVES
This project is aimed at the analysis of bush pear and its oil.The main objective of this study is to carry out proximate analysis and physio-chemical properties of African pear oil extracted by solvent methods. This physio-chemical properties determined are specific gravity, refractive index, ph value, boiling point, acid value, iodine value, peroxide value, and saponification value. To achieve the objectives of this project, it is important to:-
a) Select the best suited solvent for optimum yield.
b) Characterize the extracted oil for compositions and properties.
c) Test the suitability of the oil.
1.3 STATEMENT OF THE PROBLEM
This research work involves the analysis of African pear and its oil though the food crop African pear potential is rated one of the highest oil producing fruit crop yet it begs the question of its potential.
Furthermore, this project will answer the following questions;
i) Solvent extraction by solvent method
ii) What is the optimum yield of the particle size using n- hexane?
iii) Is there significant difference in the characterization of the extracted oil as compared to theoretical value in terms of;
1) Chemical properties (Acid value, iodine value, saponification value and peroxide value).
2) Physical properties (specific gravity, density, viscosity, refractive index).
3) Chemical composition (protein crude, fibre, carbohydrate and moisture.
1.4 SIGNIFICANCE/ECONOMIC IMPORTANCE OF THE STUDY
Characterizing the potentials of African pear/African pear oil for many purposes has several implications. Communities in the West African countries are significantly dependent on financial gain from agrarian enterprise.
It is hope that from the project, optimum extraction parameters which are quality of the oil would be established, the result would add to the data bank that could help potential industrialist who intends to go into vegetable table oil production from African pear. A crop that experiences a post harvest loss in excess of 40% in areas where malnutrition is prevalent is a problem for potentials to reclaim the lost percentage of either food or other purposes is advantageous for producers and consumers alike.
Furthermore, the development of crops with indigenous appeal can strengthen the agricultural and energy sectors of struggling economics, identifying the oils fuels quantities, whether favorable or not, will help to inform future crop and industry development.
1.5 SCOPE AND LIMITATION OF THE STUDY
In this project work, we intend to analyze and extract completely African pear and its oil. Many research work has been done in giving a detailed composition found in African pear. But this research account on the optimum route to:
i) Extraction of vegetable oil from bush pear.
ii) Separation of pure oil from the solvent.
iii) Characterization of the African pear.
iv) Characterization of the oil extracted.
Due to the low yield of the above method (mechanical method) of extraction, soxhlet and cold method of extraction are used i.e. solvent extraction.