-
Refining Of Soya Bean Oil
CHAPTER ONE -- [Total Page(s) 3]
Page 2 of 3
-
-
-
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. The phosphatidic concentration obtained from oil
previously neutralized in the miscella was of higher quality than the
phosphatidic concentration obtained from the oil of the starting
miscella. Aqueous ammonia has the advantage of being safe for the
environment because the deacidification agent can be repeated or reused.
Oils especially soyabean oil with low degree of oxidation can be fully
deacidified only with the help of the ammonia. The same effect can
frequently be achieved by a preliminary desliming with 5 percent formic
or citric acid. Deodourization at 2100c of oils that have been
deacidified with ammonia and washed with water yield bland and pale
edible oils having good storability (G.S Breck and S.C Bhatia).
List
and Erickson state that of all the unit processing operations, refining
has the most significant effect on oil quality measured by colour,
oxidative stability and storage properties.
If soyabean oil is not
properly refined, subsequent processing operation such as bleaching,
hydrogenation and deodourization will be impared so that finished
products will not fail to meet quality standards. Also, poor refining
will reduce the yield of natural oil, thereby lowering manufacturing
profits. (JAOCS, Vol. 60).
According to G.S Breck and S.C Bhatia,
caustic refining removes free fatty acid to 0.01-0.03percent level and
remove virtually all the phosphatides. Crude soyabean oil contains trace
amount (several part per million (ppm)) of prooxidant metals such as
iron and copper. Caustic refining usually removes 90-95 percent of these
metals. However, it should be emphasized that even though caustic
refining reduces metallic contamination to low levels, residual iron and
copper still remain strong prooxidants in refined oils and must be
taken in to account during storage and handling. At a constant
percentage of water, the total amount of caustic used influences colour
removal ie the more caustic used, the lower the colour of the refined
oil.
List and Erickson reported that plots of residual iron versus
residual phosphorus content of deodourized oil showed that iron
increases at phosphorus content below about 1ppm, reaches a constant
value of about 2-20ppm phosphorus, then beings to increase. Thus, the
decreased oxidative to stability at phosphorus content above 20ppm can
be explained by the sufficiently high iron content (ie greater than 0.2
ppm) which exerts a strong prooxidant effect. Similarly, decreased
stability at phosphorus content below 2ppm can also be explained because
of the increased iron content. At the same time, it should also be
pointed out that the traditional method for calculating the amount of
refining lye is based on the free fatty acid content and therefore gives
no indication of conditions leading to optimum phosphorus removal.
Phosphatide content generally exceed that free fatty acids in crude
soyabean oil by a factor of about 6. In refining process control, crude
oil is usually educated for refining cost by the American oil chemist‟s
society (AOCS) chromatographic method. (JAOCS, vol 60).
CHAPTER ONE -- [Total Page(s) 3]
Page 2 of 3
-
-
ABSRACT - [ Total Page(s): 1 ]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, ... Continue reading---
