The oil and fat products used for edible purposes
can be divided into two distinct classes:
-liquid oils, such as olive oil, peanut oil,
soybean oil, or sunflower oil; and
-plastic fats, such as lard, shortening, butter,
and margarine.
Fat and Oil Processing
Crude fat and oil derived from plant and animal sources are
subjected to several commercial refining processes before the
final products reach the consumer market.
During these processes, water, carbohydrates, proteins,
pigments, as well as phospholipids, free fatty acids, sterols,
waxes and tocopherols are removed.
In general, fat and oil undergo four processing steps:
1. Extraction
2. Refining (Neutralization or Degumming)
3. Bleaching
4. Deodorization
Fat and Oil Extraction
Rendering
Mechanical pressing
Solvent extraction
Rendering
more often employed for the extraction of fats from animal
tissues.
oil-bearing tissues are chopped into small pieces and boiled
in water
the oil floats to the surface of the water and skimmed
water, carbohydrates, proteins, and phospholipids remain in
the aqueous phase and are removed from the oil
degumming is also performed during this step to remove
excess phospholipids
the separated proteins are often used as animal feeds or
fertilizers.
Mechanical Pressing
often used to extract oil from seeds and nuts
shells or hulls of the plant materials are removed and the kernels or meats are
grinded to rupture the cellular structures
the coarse meal is then heated and pressed in hydraulic or screw presses to
extract the oil
In some cases, oil is pressed without heating. Such oil is known as coldpressed or virgin oil. It contains the least amount of impurities and is often of
edible quality without further refining.
For seeds or nuts containing a higher oil content than soybeans it became
customary to press the material in screw presses to remove a large proportion
of the oil before extraction. Since this prepressing also ruptures the cellular
structures of oil-bearing materials, most of the residual oil is easily removed
with solvents
Solvent Extraction
For seeds or nuts containing a higher oil content, not all of the oil
is removed during pressing.
Organic solvents such as petroleum ether and hexane can be
added to the pressed cake to recover the residual oil.
The oil-sovent solution will then be separated from the meal.
Finally, the solvent is evaporated from the oil.
In general, fat and oil undergo four processing steps:
1. Extraction
2. Refining (Neutralization or Degumming)
3. Bleaching
4. Deodorization
Refining (Neutralization or Degumming)
Free fatty acids, phospholipids, pigments, and waxes in the
extracted oil lead to undesirable properties of the final products.
Many of these impurities can be removed by treating fats at 40º
to 85º C with caustic soda (sodium hydroxide) or soda ash
(sodium carbonate).
In general, fat and oil undergo four processing steps:
1. Extraction
2. Refining (Neutralization or Degumming)
3. Bleaching
4. Deodorization
Bleaching
Bleaching The major purpose of bleaching is the removal or
undesire color materials in the oil.
Heated oil (~85 oC) may be treated with various bleaching
agents such as fuller's earth, activated carbon, or activated
clays.
Many impurities, including chlorophyll and carotenoid pigments,
are adsorbed onto such agents and removed by filtration.
However, bleaching also promotes lipid oxidation since some
natural antioxidants are removed together with the impurities.
In general, fat and oil undergo four processing steps:
1. Extraction
2. Refining (Neutralization or Degumming)
3. Bleaching
4. Deodorization
Deodorization
Deodorization is the final step in the refining of oils.
Deodorization involves the use of steam distillation under reduced
pressure.
In Europe, a deodorization temperature of 175 - 205º C is common, but in
the United States, higher temperatures of 235 - 250º C are usually
employed.
Volatile compounds with undesirable odors and tastes can be driven off,
resulting a odorless product.
The oil produced is referred to as "refined oil" and is ready to be consumed
or for the manufacture of other products.
About 0.01 percent of citric acid is often added during this step to
inactivate pro-oxidant metals such as iron or copper.
Food
Percentages of
Trans-Fatty Acids
Butter
3.6
Soft Margarine, High in PUFA
5.2
Soft Margarine, Low in PUFA
9.1
Hard Margarine
12.4
Vegetable Oils, Including Safflower,
0.0
Sunflower, and Soy
Beefburger, Fried or Grilled
0.8
Chocolate Cake with Icing
7.1
Trans fat has both the benefits and drawbacks of a saturated
fat.
- It has a longer shelf life than regular vegetable fat and is solid at
room temperature.
-Trans fat tends to raise "bad" LDL- cholesterol and lower "good"
HDL-cholesterol, although not as much as saturated fat.
-Trans fat is found in margarine, baked goods such as doughnuts
and Danish pastry, deep-fried foods like fried chicken and Frenchfried potatoes, snack chips, imitation cheese, and confectionary
fats.
These processes are used to modify physical properties
of an oil or fat such as melting point and consistency.
Polymerization of oils
Polymerization of oils
Peroxide value
Anisidine value
Thiobarbituric value
High saponification value means….
Iodine Value
High iodine value means…..
High AV means…….
Free fatty acid value
Example:
Tripalmitin sample has an AV of 0.025.
What is the free fatty acid value?
Peroxide value (PV)
Anisidine value
Measure……