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PROCESS FOR REFINING VEGETABLE OIL AND ITS FOOD VALUE

CHAPTER ONE

INTRODUCTION

Palm oil is one the commercial product of palm fruit (Elaesis Guineesis). It is derived from the fleshy messieurs of the fruit of the oil palm which contains 45 – 55% oil. Palm oil belongs to a class of food known as fat and oil, which are generally termed lipid. It is oil from plant origin. However, oil palm exists in a world semi and cultivated state in three kinds of the equatorial tropics:

- In Africa

- South-east Africa

- And in America

It is indigenous to West Africa and grows wild in most parts of Southern Nigeria. The oil palm gives the highest yield of oil per unit area of any crop, and produces two distinct oil. The outer fibrous layer provide palm oil, the inner hard unit contains palm kernel oil, both which are important in world trade. Though both palm oil and palm kernel are derived from the pulp during processing. The international trade in palm oil began in the beginning of the nineteenth century, while pal, kernels trade develop after 1850. Naturally, the oil palm must be harvested before processing can take place. This is usually occurs when t he fruit bunches changes colour from black to orange and fruiting body becomes detached from the stalk (Piggott, 1990; p. 109). Once the produce is harvested, it is taken to the mill for  the palm oil to be extracted. This process is carried out in four stages:

- Sterilization

- Stripping of fruitless from bunches

- Digestion

- Oil extraction

Moreover, crude vegetable oil are extracted form the seeds/nuts. Presently, it is done primarily by solvents extraction whereas in the past, it was done by physical means such as the application of heavy pressure to the seed/nut. However, palm oil constitutes the most important source of edible oils and fats. The oil is semi-solid at room temperature due to the presence of natural saturat4ed fats. It severs as rich source of dietary energy yielding approximately a calorie. Palm oil contains fatty acid components which are essential nutrients (FAO, 1966: p, 119 - 121) and their functional and textural characteristics contribute to the favour and palatability of many natural and prepared foods. It is easily digested, absorbed and to utilized in normal metabolic processes. The oil is cholesterol free and is rich in carotenoids.

Naturally, palm oil contains a high level of tocols (vitamin E) which are poverty natural anti-oxidants. It contains a very 100 concentration of linolenic acid and a moderate proportion of linolenic acid, the most readily oxidized component of oils. Natural palm oil is known for its excellent stability at high temperatures. The low content of polyunsaturated fatty acids, which centers resistance to rancidity. In addition, vitamins are accessory food factors, which cannot be synthesized in the human body, and have to be supplied in the diet, albeit in small quantities.

The fat – soluble vitamins namely:

- Vitamin A

- Vitamin D

- Vitamin E

- Vitamin K

Are contained in fat and oils. Vitamin A carotene from natural palm oil is nature’s most abundant source. In nature, there are approximately six hundred known carotenoids, rangity from yellow orange to red, lives and some of these pipmeirts possess vitamin A activity of varying degrees.

Red palm oil is one of the richest natural plant sources of carotenoids with concentration of 500 – 750 ppm. No other vegetable oil contains carotenoids in significant quantities.

Vitamin E is one of the most important phytonutrients in edible oils/. It consists of eight naturally occurring isomers a family of four tocopherots (alpha, beta, gamma and delta), and four tocotrinots (alpha, beta, ----mma and delta) homologues.

Tocotrinols are naturally present in most plants; however, they are dound most abundantly in palm oil extracted from palm fruits vitamin E anti – oxidant play protective role in cellular aging, atheroseclerosis and cancer.

Vitamin D on the other hand, is a sterol and is essential for borne formation.

            Nevertheless, the vegetable oil obtained from t h e same fruits as palm oil is very different products because of its lauric and content. It has a similar composition and behaviours of those of acid content of this oil make it a desirable ingredient in the manufacture of margarines confectionery and based goods.

This acid also gives the oil some special quantities which makes it desirable in soap manufacturing. It acts as processing acids in the rubber industry due to its softening and plastering effects.

            Oils and fat are liable to spoilage which results in the production of unpleasant odours and flavours. This is used in described as rancidity. Different types of oil and  fats show varying degree of resistance to spoilage, thus most vegetable oils deteriorate only slowly, whereas animal fat deteriorate rapidly and marine oil. This is because animal fat contain a relatively high proportion of combined high unsaturated fatty acids. The two most common forms of rancidity are hydrolytic.

            Generally, palm tree is highly valuable plant in the sense that non of its component is a waste. The palm founds could be used for there feeding of domestic animals as improvised roofs for local houses. The stem could on its own serve as alternative to plant in the conventional roof for modern building. The fruits/kernel provide goods source of vegetable oil.

            All crude oils and fats when fresh produced contain unwanted impurities.

These unwanted impurities consist of:-

-                      Free fatty acids

-                      Moisture

-                      Gums

-                      Trace metals

-                      Odourferious materials

-                      Colouring matter

-                      Resins

-                      And sometime vitamins. These impurities affect flavour, odour, and clarity and are removed during returning. Process is carried out in a number of stages which may be considered in turn:-

-                      Degummiry

-                      De odourizing

-                      Reaction with alkali

-                      Bleaching

After undergoing these process, the oil is pure and ready for use as is usually the case, ready for blending. It is desirable t hat the oil should not come into contact with air one it has been refined as this leads  to deterioration due to oxidation. The implication of these factors listed above and even more would be highly lighted in the course of this work with a view – pointing the best over all processing method.

            Finally, cholesterol a steroid lipid is found in the cell membranes of all body tissues. It is carried around the blood stream of all animals.

Cholesterol are classified into two forms:-

-                      Good cholesterol

-                      Bad cholesterol

Most cholesterol is not dietary in origin, rather it is synthesized internally. They are present in higher concentrations in tissue which either produce more or have more densely packed membranes, examples:-

-                      The liver

-                      Spinal cord

-                      And atheroma

Moreso, they play a central role in many biochemical processes. The body uses it in a number of ways namely:-

-                      In the production of bile

-                      In the production of acids

-                      Helps I n the digestion of fat in the body

-                      It is important to health.

However, too much cholesterol in the body can lead to narrowing and blockage of the arteries especially those that feed the heart and can keep it healthy.

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