REFINING OF SOYA BEAN OIL
This project work studied the refining of crude soya bean oil extracted from soya bean seed using alkali /caustic refining method. The work was carried out using phosphoric acid for the degumming /pretreatment process and sodium hydroxide for the neutralization /refining of the oil. Certain tests were carried out on both the crude and refined oil such as saponification value, acidic value, iodine value, specific gravity and viscosity, the results obtained after the tests include 42.075, 164.28, 589.05, 0.8944 and 0.038 respectively for refined oil and 44.88, 109.52, 448.8, 0.8148 and 0.035 respectively for the crude oil.
Refining of vegetable oils is essential to ensure removal of germs, phosphatides and free fatty acids (F.F.A) from the oil, to impact uniform colour by removal of colouring pigments and to get rid of unpleasant smell from the oil by removal of odiferous matter.
Refining is carried out either on batch operation or as continuous operation. With certain oils even physical refining can be carried out instead of chemical.
For processing less than thirty tones of oil per 24 hours, and when oil has F.F.A content of 1 percent or less normally batch process is recommended. Batch process involves low capital investments, simplicity of operation and low maintenance, making refining economically a viable proposition even at capacity as low as 10 tonnes per 24 hours. (According to Dietary fats and oils in Human Nutrition. (Rome 1977)).
Crude soyabean oil of good quality has a lighter amber colour which upon alkali refining is reduced to the light yellow colour of most vegetable seed oils. Soyabean oil produced from green or immature beans may contain sufficient chlorophyll to have a greenish cast but this is not usually very evident until after the yellow red pigment of the oil have been bleached in hydrogenation (G.S Breck and S.C Bhatia, 2008).
1.2 BACKGROUND OF THE STUDY
Crude fats and oils are processed by general scheme shown below with modifications or exceptions for specific species.
The soap stock can be dried if refining is done adjacent to an extraction plant or acidified again to remove fatty acids and sold to the olechemical industry. The oil is then water washed and centrifuge one or two times to remove residual soaps.
According to GS Breck and S.C Bhatia, a total degumming process for removing essentially all the phosphatide from soyabean oil using first an acid and then an alkali and two centrifuges has shown higher yields than conventional refining. This process however, does not remove prooxidant metals efficiently and for this reason has not found commercial acceptance in the united state.
G.S Breck and S.C Bhatia have stated that Dijkstra has described a novel process where the washing water is recycled to the oil feed and use to dilute concentrated alkali. This process does not generate an aqueous effluent and can be used for both acid and alkali refining, thus allowing refiners to change gradually from alkali refining to physical refining. Neutralization of soyabean oil with alkali solution assures elimination of free fatty acids without notable change in the phosphatide content.
1.3 STATEMENT OF THE PROBLEM
In the market today, most vegetable oils solidify at a low temperature of less than 250c. This work is to process and refine edible and quality soyabean oil that will not undergo solidification at a low temperature.
1.4 OBJECTIVES OF THE STUDY
The objective of refining and processing fats and oils include:
Removal of free fatty acids, phospholipids (gums) colour and off-flavour/odour compounds and toxic substances to produce light- coloured and bland products with long shelf lives.
Obtaining a mixture of the triacyl-glycerols with the desired solid content profiles over the range of product use.
Preparation and storage of semi-solid products with desired textures.
1.5 SCOPE OF THE STUDY
The crude oil extracted from soyabean needs further treatment to convert it to a bland, stable, nutrition products that is used to manufacture margarine, shortening, salad and cooking oil, mayoniaise, food products, Olechemicals.
This study entails the process of producing good quality oil through caustic/alkali refining process which is going to be compared with other good quality products in the market like grand product etc.
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