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INTERDISCIPLINARY JOURNAL OF CONTEMPORARY RESEARCH IN BUSINESS
14.1.1 DEGUMMING
Before further processing of the extracted crude oil, the crude oil has to be degummed.
Degumming removes the phosphatides and mucilaginous gums, which becomes insoluble
in the oil when hydrated. Degumming is done for two primary reasons.
i. To produce lecithin in the case of soybean and
ii. To produce an oil suitable for long term storage or transport (the presence of
substantial amount of phosphatides lead to dark coloured and off-flavoured oil).
Phospholipids has both hydrophilic and lipophilic components that makes them excellent
emulsifiers but they also allow faster spoilage of the oil because they are more
susceptible to oxidation than triglycerides. Lecithin is an important by- product of the
degumming process.
Degumming is carried out using two methods.
i. Degumming with water
ii. Degumming with acid water.
Degumming with water involves mixing the oil with about 2% water at 60-80 o C for about
30 minutes to hydrate the phosphatides, thereby reducing their solubility in the oil.
Degumming with acid and water follows a similar procedure, except the oil is first
vigorously mixed with about 0.1-0.5% of 50% solution of citric acid, malic acid or
phosphoric acid and then mixed gently with 2% water. Degumming with acid and water
also removes the non-hydratable phosphatides. Following contact of the oil with water or
acid and water, the oil is centrifuged to remove the precipitated materials.
14.1.2 BLEACHING.
With few exceptions such as olive oil, consumer expect their oil to have little or no
colour. In addition, many pigments are pro-oxidants that will make the oil more
susceptible to oxidation.
Alkali refined oil must be bleached to remove pigments, metallic components, residual
soaps and traces of oxidation products. The exact process varies depending on the
equipments used in the bleaching process.
The process generally involves mixing the oil with bleaching earth (an acid treated
bentonite clay) at about 100 o C under vacuum for about 5-30minutes.The amount of the
activated bleaching earth used variesfrom1-3% depending on the level of the residual
phosphatides present in the oil. The bleaching earth is a natural clay of aluminium silicate
containing magnesium, calcium, sodium and iron; with PH 8, and apparent density of 0.7-
0.9gml. The clay, absorbed components and precipitated materials are removed by
filtration. Bleaching of the oil can be achieved in the following ways:
i. By adsorption on solids
ii. By leaching
iii. By catalytic hydrogenation
iv. By chemical bleaching agent.
COPY RIGHT © 2011 Institute of Interdisciplinary Business Research 75
JANUARY 2011
VOL 2, NO 9