Edible oil refining process
Edible oil refining process:
Dive into the intricate world of the edible oil refining process, where crude oils undergo meticulous purification to meet stringent quality standards. From degumming to deodorization, explore the key stages involved, highlighting the technologies and techniques utilized for enhancing the flavor, appearance, and shelf life of edible oils.
Processes have been developed for the refining of edible oils and fats.
1. Physical refining
and
2. Chemical refining.
The objective of refining:
1. Removal of
undesired products from crude oils
· Free fatty acids (FFA)
· Phospholipids (gums)
· Oxidized products
· Metal ions
· Color pigments
· Others
2. Preservation of
valuable vitamins
3. Minimize oil
losses.
4. Protection of
the oil against degradation.
Steps of the chemical refining process:
1. Degumming: Reduction
of phospholipid (gum) content
2. Neutralization:
Removal of free fatty acids and residual gums
3. Bleaching: Removal of
color pigments and metal ion s
4. Deodorization:
Removal of odors
Chemical Refining:
Degumming:
Chemicals (Phosphoric acid)
Degumming may be
considered the first step in the refining process. This process is designed to
remove the phosphatides that interfere with subsequent processing and
especially for processors with an integral disposal option of gums. Crude
soybean oil has high levels of phosphorus, which can be removed in degumming
step. The oil has two kinds of gums, hydratable (phospholipids) and non-hydratable
(partially hydrolyzed phospholipids, which form salts of calcium, magnesium and
iron). The hydra tables are easily separated by treating of crude oil with hot
water (deionized water at 75°C, at a rate of 1-3%, of oil weight), followed by
centrifugation. Contrarily, nonhydratable gums are more soluble in oil than the
first and require an additional treatment with phosphoric acid (0.1-0.3% of 85%
solution) during this operation, phosphorus levels are reduced from 800-1200 to
100 ppm when hydratable gums have been removed and they can be reduced to 30
ppm if non-hydra tables are efficiently removed. It is important to know the
amount of tocopherols that are lost with gums in order to maintain the
nutritional quality of oil in this operation.
Oil Temperature: 80 – 90
°C
Neutralization:
Chemicals Caustic soda (NaoH)
1. neutralizes the free
fatty acids by saponification them into sodium salts.
2. Saponification and
hydrates phospholipids
3. Removes colour
pigments
4. Concentration: 12 –
24 °Bé
Addition: stoichiometric
amount to neutralize the phosphoric acid and the free fatty acids plus an
excess of 0 – 40 %
Calculation: 0,142 kg NaOH (100%) per kg FFA + 0,816 kg NaOH
(100%) per kg H3PO4 (100%)
Example: If CDSO flow 10000 kg/hr,
F.F.A=0.8% = (.8/100*10000) kg=80 kg
H3Po4 =0.15% =15Ltrs =8.86kg (Approx.)
NaOH = (0.142*80) kg+ (8.86*0.816) kg
=18.59Kg
&
Water to wash out residual soaps and to
dilute the caustic soda.
Water Quality: soft,
demineralized water
Temperature: min. 90°C
Addition for washing: 5 – 10 %
The addition of an alkali solution to crude or crude degummed
soybean oil results in chemical reactions and physical changes. The alkali
combines with the free fatty acids present to form soaps; the phosphatides and
gums absorb alkali and are coagulated through hydration or degradation; much of
the coloring matter is degraded, absorbed by the gums, or made water-soluble by
the alkali; and the insoluble matter is entrained with the other coagulable
material. If excess caustic is used, prolonged exposure to heat will result in
saponification of the oil, with resultant oil losses.
The final water-washed oil go directly to the bleaching
processing.
Bleaching:
Bleaching is the most delicate stage.In this step, unwanted substances are removed, such as
pigments, trace metals, phospholipids and some degradation products. However,
some valuable compounds such as tocopherols and sterols can be removed,
resulting in significant loss of oxidative stability and increased fatty acid
content. To avoid this negative oil change, bleaching parameters such as
bleaching clay concentration, temperature and duration should be optimized.
Since the bleaching conditions depend on the properties of the bleaching clay
as well as the type of crude oil, the bleaching parameters should be optimized
with different types of clay for each vegetable oil. Since such
optimization has not yet been reported for soybean oil treated with Tonsil
Supreme Bleaching Absorbent, this study investigated the effect of bleaching
parameters (tocopherols and sterols) on bleaching efficiency, oxidative
stability, and composition of constituents and bioactive compounds. By doing
this type of oil uses the soil mentioned above. The results showed that
clay content had the greatest effect on bleaching efficiency, especially on
clarity and phosphorus content, according to the Lovibond scale. Temperature
and clay content significantly affect oxidative stability, particularly the
formation of secondary oxidation products. Increasing the clay content
decreases the tocopherol content of the bleached oil. Neutralized soybean oil
at 105 °C for 20 min at 1% Tonsil supreme activated bleaching clay showed the
highest oxidative stability, the best bleaching performance and the most
favorable sterol content, although the tocopherol content was reduced.
Deodorization:
Deodorization is a very important
consideration in soybean oil processing. Deodorization temperature should not
exceed 255oC, with an optimum range of 245oC ~ 250oC. Deodorization
efficiency is a function of the following parameters: Absolute
pressure. Maximum temperature, time or throughput rate, and stripping
stream rate. However these parameters are adjusted, the objective is to produce
the best quality soybean oil. Such oils shall exhibit a maximum of 0.03% FFA
and a Lovibond color value of a maximum of 10.0 yellow and less than 1
red, and tasteless. For best quality soybean oil, Deodorizer contact with oil
must be stainless steel. The use of mild steel will not produce good quality
soybean oil. A final critical consideration in deodorization is the
addition of at least 50 ppm citric acid to the cooling section of the
deodorizer. Although some manufacturers recommend adding citric acid before and
after deodorization, this is of questionable value. Citric acid added prior to
deodorization is thermally destroyed in the process and thus may have no
obvious benefit. Refine soybean oil must be stored below 40oC. for
its stability.
And finally before bottling filling 15 to 30 ppm Vitamin A add into the
oil.
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