Everything about Vegetable Fat totally explained
Vegetable fats and oils are substances derived from plants that are composed of
triglycerides. Nominally, oils are liquid at
room temperature, and fats are solid; a dense brittle fat is called a
wax. Although many different parts of plants may yield oil, in actual commercial practice oil is extracted primarily from the
seeds of oilseed plants.
The temperature-based distinction between oils and fats is imprecise, since definitions of room temperature vary, and typically any one substance has a
melting range instead of a single
melting point.
Triglyceride vegetable fats and oils include not only edible, but also inedible vegetable fats and oils such as processed
linseed oil,
tung oil, and
castor oil, used in lubricants, paints, cosmetics, pharmaceuticals, and other industrial purposes. Although thought of as
esters of
glycerin and a varying blend of
fatty acids, in fact these oils contain free fatty acids and
diglycerides as well.
Uses of triglyceride vegetable oil
Oils extracted from plants have been used in many cultures, since ancient time. As an example, in a 4,000 year old "kitchen" unearthed in
Indiana's
Charlestown State Park, archaeologist Bob McCullough of
IPFW found evidence that natives used large slabs of rock to crush
hickory nuts, then boiled them in water to extract the oil.
Fatty acids play an important role in the life and death of cardiac cells because they're essential fuels for mechanical and electrical activities of the heart.
Culinary uses
Many vegetable oils are consumed directly, or used directly as ingredients in food - a role that they share with some
animal fats, including
butter and
ghee. The oils serve a number of purposes in this role:
- Texture - oils can serve to make other ingredients stick together less.
- Flavor - while less-flavorful oils command premium prices, oils such as olive oil or almond oil may be chosen specifically for the flavor they impart.
- Flavor base - oils can also "carry" flavors of other ingredients, since many flavors are present in chemicals that are soluble in oil.
Secondly, oils can be heated, and used to cook other foods. Oils that are suitable for this purpose must have a high
flash point. Such oils include the major cooking oils -
canola,
sunflower,
safflower,
peanut etc. Some oils, including
rice bran oil, are particularly valued in
Asian cultures for high temperature cooking, because of their unusually high flash point.
Hydrogenated oils
Triglyceride-based vegetable fats and oils can be transformed through partial or complete
hydrogenation into fats and oils of higher melting point. The
hydrogenation process involves
"sparging" the oil at high temperature and pressure with
hydrogen in the presence of a
catalyst, typically a powdered
nickel compound. As each double-bond in the
triglyceride is broken, two hydrogen atoms form single bonds. The elimination of double-bonds by adding hydrogen atoms is called
saturation; as the degree of
saturation increases, the oil progresses towards being fully hydrogenated. An oil may be hydrogenated to increase resistance to
rancidity (
oxidation) or to change its physical characteristics. As the degree of saturation increases, the oil's viscosity and melting point increase.
The use of
hydrogenated oils in foods has never been completely satisfactory. Because the center arm of the
triglyceride is shielded somewhat by the end
triglycerides, most of the
hydrogenation occurs on the end
triglycerides. This makes the
resulting fat more brittle. A margarine made from naturally more saturated tropical oils will be more plastic (more "spreadable") than a margarine made from hydrogenated soy oil. In addition, partial hydrogenation results in the formation of
trans fats, which have increasingly been viewed as unhealthy since the 1970s.
(In the U.S., the USDA Standard of Identity for a product labeled as vegetable oil margarine
specifies that only canola, safflower, sunflower, corn, soybean, or peanut oil may be used. Products not labeled vegetable oil margarine
don't have that restriction.)
Industrial uses
Vegetable oils are used as an ingredient or component in many manufactured products.
Many vegetable oils are used to make soaps, skin products, candles, perfumes and other personal care and cosmetic products.
Some oils are particularly suitable as drying agents, and are used in making paints and other wood treatment products. Dammar oil (a mixture of linseed oil and dammar resin), for example, is used almost exclusively in treating the hulls of wooden boats.
Vegetable oils are increasingly being used in the electrical industry as insulators as vegetable oils are non-toxic to the environment, biodegradable if spilled and have high flash and fire points. However, vegetable oils have issues with chemical stability (there has to be a tradeoff with biodegradability), so they're generally used in systems where they're not exposed to oxygen and are more expensive than crude oil distillate. Two examples are FR3
by Cooper Power and Biotemp by ABB. Midel 7131 by M & I materials is a synthetic tetraester, like a vegetable oil but with four fatty acid chains compared to the normal three found in a natural ester, and is manufactured by an alcohol plus acid reaction. Tetraesters generally have high stability to oxidation and have found use as engine lubricants.
Vegetable oil is being used to produce bio-degradable hydraulic fluidand lubricant.
Common vegetable oil has also been used experimentally as a cooling agent in PCs.
One limiting factor in industrial uses of vegetable oils is that all such oils eventually chemically decompose turning rancid. Oils that are more stable, such as Ben oil or mineral oil, are preferred for some industrial uses.
Vegetable-based oils, like castor oil, have been used as medicine and as lubricants for a long time. Castor oil has numerous industrial uses, primarily due to the presence of hydroxyl groups on the fatty acid chains. Castor oil, and other vegetable oils which have been chemically modified to contain hydroxyl groups, are becoming increasingly important in the production of polyurethane plastic for many applications. These modified vegetable oils are known as natural oil polyols.
Pet food additive
Vegetable oil is used in production of some pet foods. AAFCO defines vegetable oil, in this context, as the product of vegetable origin obtained by extracting the oil from seeds or fruits which are processed for edible purposes. In some poorer grade pet foods, the oil is listed only as "vegetable oil", without specifying the particular oil.
Fuel
Vegetable oils are also used to make biodiesel, which can be used like conventional diesel. Some vegetable oil blends are used in unmodified vehicles but straight vegetable oil, also known as pure plant oil, needs specially prepared vehicles which have a method of heating the oil to reduce its viscosity. The vegetable oil economy is growing and the availability of biodiesel around the world is increasing.
Extraction
The "modern" way of processing vegetable oil is by chemical extraction, using solvent extracts, which produces higher yields and is quicker and less expensive. The most common solvent is petroleum-derived hexane. This technique is used for most of the "newer" industrial oils such as soybean and corn oils.
Another way is physical extraction, which doesn't use solvent extracts. It is made the "traditional" way using several different types of mechanical extraction. This method is typically used to produce the more traditional oils (for example, olive), and it's preferred by most "health-food" customers in the USA and in Europe. Expeller-pressed extraction is one type, and there are two other types that are both oil presses: the screw press and the ram press. Oil seed presses are commonly used in developing countries, among people for whom other extraction methods would be prohibitively expensive. The amount of oil extracted using these methods varies widely, as shown in the following table for extracting mowrah butter in India:
Further Information
Get more info on 'Vegetable Fat'.
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