Oil palm (Elaeis guineensis) is believed to have originated from the tropical rainforest of West Africa. It is a perennial plant that belongs to the family palm distinitive group of the monocotyledons (Tong and Teog 1995). The main belt runs through the Southern Latitude of Cameroon, Ivory Coast, Ghana, Nigeria, Sierra-Leona and Conga (Tong and Teoh 1995).
Palm kernel oil is an oil which is extracted from the seed of the palm. The monocarp of the fruit can be extracted for palm oil. This palm oil contains natural antioxidant (Tocopherol) and carotene which are pro-vitamin A (Faessler et al 2007).
Palm kernel oil has a great preponderance of saturated fatty acids than palm oil (80% compared to 60% for palm oil) with the major fatty acid being oil (Ihekeronye and Ngoddy, 1995). It also contains the low molecular weights fatty acids, caprylic and capric acid. In line with the high proportion of saturated acid, saturated triglycerides constitute over 60% and mono-oleic di-saturated triglycerides more than 25% of the total glycerides. The Lodine value is about 17 and the melting point 25 – 30oC (Ihekeronye and Ngoddy 1985).
Palm kernel oil, coconut oil and palm oil are three of the few highly saturated vegetable fats. Palm kernel oil which is semi-solid at room temperatures is more saturated than palm oil and comparable to coconut oil like. All vegetable oil these three palm – derived oils do not contains cholesterol (found in unifined animal fats), although saturated fat in take increase both L D L and H D L cholesterol (Mansink and Katan 1992).
Palm kernel cake is useful as a source of protein in compounding animal feed and has a favourable calcium to phosphorus ratio. An average analysis of palm kernel cake is a shown in table I
Table I Analysis of Palm Kernel Cake
Source: Raw materials Research and Development Council on Oil Palm 2004.
There are a number of ways to extract palm kernel oil from the seeds, ranging from traditional method which involves roasting the seeds, cracking them and grinding then to extract the oil to more modernized methods. Which are designed to extract every possible drop of oil from seeds. Several manufacturers also use a fractional distillation process to separate the oil into various components.
However the quality oil varies widely depending on the method of processing adopted, the quality control measure applied and storage techniques employed. Other factors which may affect quality of palm oil are. The presence of excess moisture which leads to the development of free fatty acid (F F A) by enzymatic hydrolysis of the oil (Ishiwu and Iwouno 2006).
Exposure to air at high temperature leading to autoxidation of oil and rancidity.
Palm kernel oil are used in the production of refined vegetable oil, it is used either in blends or alone with other oils for the manufacture of cocoa butter substitutes and confectionary fats, filled milks, table margarine and many other food products. Non-food product like soap, fatty acid and glycerine, bio fuel and the manufacturing of Oleo chemicals which include methyl/esters, fatty alcohols, etc.
Some refined vegetable oil congeal at room conditions while others remain molten. The presences of high content of saturated oils are fats is responsible for the congealing of those oil.
Observation on palm oil reveal that palm oil produced from unboiled palm fruit congeals at room conditions whereas those boiled palm fruits do not congeal at room temperature. This study therefore intends to find out if palm kernel oil processed using kernel from boiled unboiled palm fruits could follow the same trend. In other wards whether boiling of palm fruit could result in the palm kernel oil more molten than palm kernel oil from unboiled, effect of pre-processing conditions on the characteristics of palm kernel oil.
2.1 HISTORICAL DEVELOPMENT OF PALM KERNEL OIL
The development of oil palm (Elacis guineensis) starts about 2 week after an thesis (WAA); at 8WAA the endosperm of the seed is liquid and at 10 WAA, it is semi gelatinous (Hartley el al, 1998): At 12 WAA oil start to deposit in the endosperm and almost complete by 16WAA. During this period the endosperm and endocarp slowly harden and by 16WAA the endocarp is hard shell enclosing a hard whitish endosperm which is known as kernel, (Oo et al, 1985), Sambanthamurthi et al, 2000). Oil deposit in the Mesocarp start at about 15WAA and continues until fruit maturity (about 20 WAA, Bafor and Osangie, 1986). Oo et al (1985), also observed that as the total lipid progressively increases (0.1-48%) in the Mesocarp the Moisture Content decreases (88-37%) with increasing WAA.
The tree is generally believed to have originated in the jungle forests of East Africa and there is some evidence that palm oil was used in Egypt at the time of the pharaohs, some 5000 years age (Cottrel, 1991) but now its cultivation is mostly in South East Asia.
There are three main varieties of oil palm distinguished by their fruit characteristics. These are.