Table 1. Physico Properties of Chrysophyllum Albidum
The exploration of under utilized plant seeds as sources of industrial oil was the main focus of the work. The research work was carried out to ascertain the viability of seeds of an African star apple as a source of oil for industrial use. Oils were extracted from dried seeds of African star apple using n-hexane by Soxhlet extraction method. A comprehensive range of physicochemical properties, namely: free fatty acid, peroxide value, saponification value, iodine value, and specific gravity were determined. The characterization of the oil was done according to the methods described by the Association of Official Analytical Chemist. The percentage yield of the oil was 2.5%, dark yellow in colour and liquid at room temperature. Saponification value of the oil was 51.45, Iodine value was 19.20, Peroxide value stood at 1.78, and Specific gravity was 0.91. The low yield and values of saponification and iodine show that, the oil is not viable for industrial use.
Chrysophyllum Albidum Linn (African Star apple) is a large berry that contains up to five seeds that are flat in shape. The plant belongs to the family Sapotaceae. It is primarily a forest tree species, whose natural occurrences have been reported in diverse ecozones of Africa, Nigeria inclusive ( Bada, 1997). The leaves of the plant are alternate and nearly evergreen elliptic, slightly leathery, and are used in ethnomedicine ( Adewusi, 1997). The fruit could be ellipsoid, round or pear shaped. It has a milky sweet pulp that house the seeds. When the fruit is cut transversely, it appears like an asterisk in the central core or like pointed stars. This is the origin of the name of the fruit as “Star Apple”. The flesh fruit is eaten raw by most people and is rich in Iron and vitamin C and is a good source of raw material for some industries ( Muanya, 2010). While the pulp is eaten, the seeds are relished by many others.
The African Star apple plant often grows to a height of 36.5 m though it may be smaller. The seeds are also used for local games. Chrysophyllum Albidum fruit is common in both urban and rural centres, especially, during the month of December to April. The fruits are not usually harvested from the trees, but left to drop naturally to the forest floor, where they are picked. Care must be taken to make sure that they are fully mature. Otherwise, the fruits will be gummy, astringent and inedible. When fully ripe, the skin is dull, a trifle wrinkled, and the fruit is slightly soft to the touch. The ripe fruit, because of its mucilaginous character, is eaten to soothe inflammation in lar yngitis and pneumonia. It is given as a treatment for diabetes mellitus, and as a decoction is gargled to relieve angina. In Venezuela, the slightly unripe fruits are eaten to overcome intestinal disturbances ( Burkill, 1985).
The roots, barks and leaves of Chrysophyllum Albidum tree have been employed in folk medicine for the treatment of diseases. The bark is used for the treatment of yellow fever and malaria, while the leaf is used as an emollient and for the treatment of skin eruption, stomach ache and diarrhoea. The cotyledons from the seeds of Chrysophyllum Albidum are used as ointments in the treatment of vaginal and dermatological infections in Western Nigeria ( Muanya, 2010). The seeds contain 1.2% of the bitter, cyanogenic glycoside, lucumin; 0.0037% pouterin; 6.6% of a fixed oil; 0.19% saponin; 2.4% dextrose and 3.75% ash. The leaves possess an alkaloid, resin, resinic acid, and a bitter substance. The seeds are usually thrown away except for the purposes of propagation ( Nwadinigwe, 1982).
The desire to conserve resources spent on the importation of oil for industrial use has increased the search for new sources of oil to complement the traditional ones. There has been a focus on non-utilised oil seeds for possible development and use ( Obasi, and Okolie, 1993).
Akubugwo and Ugbogu (2007) studied the Physicochemical studies on oils from five selected Nigerian plant seeds. They extracted oils from four underutilized seeds of the Nigerian plants Chrysophylum albidum, Dacryoides edulis, Landolphia owariensis and Napoleona imperialis using n-hexane and their physicochemical properties compared with oils from the seeds of Elaeis guinensis. The four seed oil was odourless and at room temperature liquids as against E. guinensis seed oil that were semi-solid under the same condition. Specific gravity of the seed oils ranged from 0.82 to 0.94, while peroxide value for all the oil extracts except that from D. Edulis seed were less than three. Saponification values were as low as 42.40 in L. Owariensis and as high as 246.60 in E. Guinensis seed oils. Iodine values were between 15.10 and 45.00 in the extracts. Their results suggest that C. Albidum and D. Edulis seeds may be viable sources of oil going by their oil yield. However, the studied characteristics of all the oil extracts in most cases is compared favourably with E. Guinensis seed oil, which is presently used for many domestic and industrial purposes in Nigeria.
Ajiwe, et al., (1996) studied the applications of oil extracted from African star apple (Chrysophyllum Africanum), Horse eye bean (Mucuna Sloanei) and African pear (Dacryodes Edulis) seeds. Oils were extracted from the dried seeds of African star apple, horse eye bean and African pear by Soxhlet method. The yield of the oils were 25.00 ± 0.5%, 23.00 ± 0.65% and 27.28 ± 0.82%, respectively. The star apple oil was deep red; horse eye bean and African pear had similar light yellow colours. The saponification value of the African star apple was low, that of African pear was medium, while that of horse eye bean was high. Iodine values of both horse eye bean and African pear were high, while that of the African star apple was very low. The free fatty acid and acid values of the star apple suggested that, fatty acids could be prepared from it. The acid and free fatty acid contents of African pear showed that, the oil would not need purification, while the horse eye bean would need little purification. The iodine values of the oil suggested that the African star apple can be used for the preparation of solid soap; African pear and Horse eye Bean are used for the preparation of resin, paint, polish, wood varnish and skin cream. The horse eye bean was also a constituent of liquid soap, while the African pear was used in grease.
The Proximate and Mineral Composition of the Seed Shell Pericap of Chrysophyllum Albidum have been studied by Ewansiha et al. (2011). Their aim was to show the relevance of seed shell pericap of Chrysophyllum Aibidum in water and wastewater treatment among other uses. The results show viz: moisture content 12.90%, ash content 1.27%, crude fibre 14.82%, crude fats 2.38%, protein 0.98%, and carbohydrates 67.65%, while the mineral composition determined using standard analytical tools were measured in mg/100g, viz: P = 10.80, Ca = 31.04, Mg = 0.61, Na = 0.36, K = 2.30, Fe = 35.20, Zn = 100, and Mn = 0.40.
The objectives of this study include:
The seed of an African Star apple (C. albidum) is the major raw material used in this research work. The seeds of C. albidum were collected from Relief market Owerri, Imo State, Nigeria from January to March 2011.
The n-hexane was used as an analytical grade and are the products of Sisco Research Laboratory, India.
The collected seeds were dehauled manually for two days, sun-dried for one week and kept until when needed. 500g of the seeds were measured and then grounded using an electrical powered plate grinding machine to achieve fine particle size for the extraction of the oil.
Solvent Extraction method was used in this research work. In the method, a hydrocarbon solvent is added to the plant material to help dissolve the essential oil. When the solution is filtered and concentrated by distillation, a substance containing resin (resinoid), or a combination of wax and essential oil (known as concrete) remains.
The ground seed was put in a conical flask. Normal hexane solvent was added to the ground seed material and it was covered, and then allowed to stand for two days. This was to help dissolve the essential oil. The solution was then filtered and the filtrate is transferred into a Soxhlet extractor to separate the solvent from the oil. The extracting solvent was recollected back via distillation, while the oil was collected separately for analysis. This extraction was done in the Soil laboratory of the Federal University of Technology, Owerri.
Free Fatty Acid was determined, as percent by mass oleic, palmitic or laurie acid, using the procedure described in A.O.A.C. (2002).
The weight (mg) of active oxygen contained in one gram of the oil or fat, were determined following the method as described by A.O.A.C (2002).
The number of grams of iodine absorbed by 100 parts by weight of the oil or fat, was determined using the method reported in A.O.A.C (2002).
It is the number of milligrams of KOH required to neutralize the fatty acids resulting from complete hydrolysis of one gram of oil, was determined according to the procedure described by A.O.A.C (2002).
It was determined using the specific gravity bottle, according to the method described by Onwuka (2005) .
The experimental results obtained from the research show that, the oil yield was low and physicochemical parameters such as, Free Fatty Acids (FFA), Peroxide Value, Iodine Value, Saponification Value, and Specific Gravity of the entire oil sample examined have yielded low values.
The percentage oil yield for the C. albidum out of the 500g is 2.5%. This is far below the value of 25.00 ± 0.5%, and 12.0% ± 0.9% as reported by Ajiwe, et al., (1996), and Akubugwo, and Ugbogu, (2007) respectively, upon greater quantity of the seed (500g) was used. This however, made the oil yields for the studied seeds to be classified as low yield as opposed to the average yield as classified by Akubugwo, and Ugbogu, (2007). At room temperature (29˚C), the seed oil is liquid. The star apple oil was dark yellow. The specific gravity obtained was 0.91 (Table 1). The value suggests that the seed oil does not have an offensive odour.
Table 1. Physico Properties of Chrysophyllum Albidum
The saponification value was 51.45 mg KOH/g as shown in Table 2. The low saponification value obtained suggests that, the oil may not be industrially useful. However, Akubugwo and Ugbogu (2007) reported a value of 126.30 for C. Albidum. The iodine value is the measure of the level of unsaturation in the oil samples. The iodine value obtained was 19.20 Wij's (Table 2). This is far below the recommended Iodine value of Nigerian Industrial Standards (NIS, 1992) for industrial standards of oils. This was in line with the value as reported by Ajiwe, et al., (1996) and also in contrast to the work as reported by Akubugwo and Ugbogu (2007). The peroxide value determines the extent to which the oil has undergone rancidity, thus it could be used as an indication of the quality and stability of fats and oils Ekwu and Nwagu, (2004). The value of 1.78 meq O2 /kg is within the recommended SON value (SON 2000).
Table 2. Chemical Properties of Chrysophyllum Albidum
The extraction and characterization of oil from Chrysophyllum Albidum seed has been done. The experimental results showed that, Chrysophyllum Albidum seed yielded a low quantity of oil (2.5%) from the 500g weight of the seed used. From the comprehensive physicochemical parameters analysed, it was seen that, low Saponification (51.45 mg KOH/g) and Iodine (19.20 Wij's) values were recorded. This is in contrast to the earlier work done by Akubugwo and Ugbogu. They concluded in their work that, the seed oil has a potential for the development for the use as domestic and industrial oils. From the experimental results, the Chrysophyllum Albidum seed oil is classified as very low yielding oil and it is said to be non-potential for the development for the use as industrial oils.