Palm oil is an edible vegetable oil obtained from the fleshy portion or the mesocarp of the fruit of oil palm trees(Elaeis guineensis). Palm oil in crude form is semi-solid and naturally reddish colour due to high amount of beta-carotene.
Palm kernel oil is an edible vegetable oil obtained from the kernel of the fruit of oil palm trees(Elaeis guineensis). Palm kernel oil in crude form is naturally yellowish in colour. The kernels oil is extracted by pressing the kernels in mechanical screw presses. The chemical composition of palm kernel oil is different from palm oil but similar to coconut oil. It is a lauric type oil.
The aim of refining is to convert the crude oil to quality edible oil by removing undesirable components or impurities to the desired levels in the most efficient manner. The impurities or undesirable components are such as free fatty acids (FFA), oxidation products, phospholipids, odiferous components, colouring matter, moisture, insoluble materials and trace metals. These components can either be present naturally in the oil or picked up from wear and tear of the extraction machinery or can form as result of quality deterioration during storage, transportation and handling. There are two routes are taken to process crude oil into refined oil, i.e., chemical and physical refining.
The main difference of the two processes is the ways of removing the FFA. Most of the refineries in Malaysia use the physical refining. During the conventional refining process, the natural carotenes (pro-Vitamin A) and a substantial portion of vitamin E found in palm oil were destroyed. However, with the new refining technology, most of these natural carotenes and vitamin E may be retained.
The methods differ basically in the way the fatty acids are removed from the oil.
a. Chemical Refining:
Chemical refining differs from physical refining particularly to the removal of free fatty acids by alkali, i.e. caustic soda (sodium hydroxide) or sodium carbonate (soda ash) is either singly or in combination and this results the production of soap stock, which have to be acidulated to acid oil. The chemical refining process is illustrated as follows:
b. Physical Refining:
Physical or steam refining or distillative deacidification process involves subjecting the oil to steam distillation under high temperature and efficient vacuum for removal of fatty acids or FFA. There is no caustic soda is required for the neutralization and hence the refining losses and costs are much lower as compared to chemical refining. The physical refining process is illustrated as follows:
Malaysian refiners are able to offer a wide range of palm products to cater for a multitude of usage worldwide. This is accomplished through a simple process of fractionation.
Fractionation of the oil is the process to segregate or separate into various glyceride fractions or the higher melting point triglycerides from the lower melting point triglycerides under controlled cooling conditions.
Palm and palm kernel oil is consists of a mixture of triglycerides with different melting characteristics. To add value to these products, the oil is fractionated by crystallization to achieve a separation of the two components. The higher point of triglycerides or fraction is known as stearin (solid fraction) and the lower point triglycerides or fraction is known as olein (liquid).
There are basically three methods of fractionation used commercially, i.e. (i) dry fractionation (ii) detergent fractionation and (iii) solvent fractionation.
Hydrogenation of fats is the addition of hydrogen to the double bonds in the fatty acid chains. It results in the hardening of oils and forms a semi-solid product.
Two major objectives are accomplished through hydrogenation of fats, i.e. (i) to convert a liquid oil to semisolid form that is more suitable for specific food applications such as margarines and shortenings, and (ii) to improve the oxidative stability of the oil.
A major disadvantage of the hydrogenation process is the formation of trans-fats. Research has shown that trans-fats have detrimental effect of trans-fat on cholesterol.
Interesterification changes the physical properties and triglycerides compositions of the oils or fats or their mixtures, without altering their fatty acid acid compositions. By the use of an alkaline catalyst, it is possible to arrange the fatty acids in oil random manner (random interesterification) with respect to the positions of the glycerol moiety. A modification of this process is to lower the temperature until some newly formed high melting triglycerides (mostly trisaturated ones) or solid is crystallise out (directed interesterification).
Interesterication is s a useful modification method that leads to different physical properties of the oil/fat to the functionality desired for a finished product.
The term bleaching refers to the treatment that is given to remove colour-producing substances and to further purify the fat or oil. The usual method of bleaching is by adsorption of the colour producing substances on an adsorbent material. Acid activated bleaching earth or clay, sometimes called bentonite, is the adsorbent material that has been used most extensively. Activated carbon is also used as a bleaching adsorbent to a limited extent.
Deodorisation is the treatment of fats and oils to remove trace elements that give rise to undesirable flavours and odours. Normally this is accomplished after refining and bleaching. The deodorization of fats and oils is simply the removal of the relatively volatile components from the fat or oil using live steam.
Normally deodorization is carried out under vacuum to facilitate the removal of the volatile substances, to avoid undue hydrolysis of the fat, and to make the most efficient use of the steam. Deodorization does not have any significant effect upon the fatty acid composition of the fat or oil.
Palm oil is approximately 50% saturated fat and 50% unsaturated fat. Due to such a unique characteristic palm oil may be separated under controlled thermal conditions into two components, a solid form (stearin) and a liquid form (olein).
Palm oil may be used to make trans-free products. For example, palm stearin can therefore be utilized to form more solid fats without the need of hydrogenation, and thus being trans- free. Palm oil is also known for its excellent stability, and can be used for frying without the need of hydrogenation, and thus creating trans-free oil for frying.
Palm oil including palm kernel oil may be used either as food or non-food uses.
In food uses, palm oil can be used to produce products such are shortenings, margarine, cooking oil, vanaspati, confectionary or specialty fats. It can also be incorporated into many food products including hot beverages, ice-cream, coffee creamers, bakery products, etc.
Palm oil is also known for its excellent stability. Hence, it is a preferred choice in the world as frying oil for foods such as instant noodles, French fries, potato crisps, doughnuts and fried meats and snacks.
The non-food uses of products such as soaps, biofuels, candles, cosmetic products, rubber processing, lubricants, printing ink , washing and cleaning raw materials etc.
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