Vegetable fats and oils
are lipid materials derived from plants. Physically, oils are
liquid at room temperature, and fats are solid. Chemically, both
fats and oils are composed of triglycerides, as contrasted with
waxes which lack glycerin in their structure. Although many
different parts of plants may yield oil, in commercial practice,
oil is extracted primarily from seeds.
The melting temperature distinction
between oils and fats is imprecise, since definitions of room
temperature vary, and typically natural oils have a melting
range instead of a single melting point.
Vegetable fats and oils may be edible or
inedible. Examples of inedible vegetable fats and oils include
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, fats and oils also typically
contain free fatty acids, monoglycerides, and diglycerides.
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.
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:
to give pastry a crumbly texture .
oils can serve to make other ingredients stick together less.
while less-flavorful oils command premium prices, oils such as
olive oil or almond oil may be chosen specifically for the
flavor they impart.
- oils can also "carry" flavors of other ingredients,
since many flavors are present in chemicals that are soluble in
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.
Unsaturated 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 is broken, two hydrogen atoms each form single bonds
with the two carbon atoms.
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 fatty acids,
most of the hydrogenation occurs on the end fatty acids. This
makes the resulting fat more brittle.
A margarine made from naturally more
saturated oils will be more plastic (more "spreadable")
than a margarine made from, say, hydrogenated soy oil. In
addition, partial hydrogenation results in the formation of
large amounts trans fats in the oil mixture, which, since the
1970s, have increasingly been viewed as unhealthy.
History in North America
While olive oil and other pressed oils
have been around for millennia, Procter & Gamble researchers
were innovators when they started selling cottonseed oil as a
creamed shortening, in 1911. Ginning mills were happy to have
someone haul away the cotton seeds. Procter & Gamble
researchers learned how to extract the oil, refine it, partially
hydrogenate it (causing it to be solid at room temperature and
thus mimic natural lard), and can it under nitrogen gas.
Compared to the rendered lard Procter
& Gamble was already selling to consumers, Crisco was
cheaper, easier to stir into a recipe, and could be stored at
room temperature for two years without turning rancid. (Procter
& Gamble sold their fats and oils brands - Jif and Crisco
- to The J.M. Smucker Co. in 2002.)
Soybeans were an exciting new crop from
China in the 1930s. Soy was protein-rich, and the light
tasteless oil was extremely high in polyunsaturates.
Henry Ford established a soybean research
laboratory, developed soybean plastics and a soy-based synthetic
wool, and built a car almost entirely out of soybeans.
Roger Drackett had a successful new product with Windex, but he
invested heavily in soybean research, seeing it as a smart
investment. By the 1950s and 1960s, soybean oil had become the
most popular vegetable oil in the US.
In the mid-1970s, Canadian researchers
developed a low-erucic rapeseed cultivar. Because the word
"rape" was not considered optimal for marketing, they
coined the name "canola" (from "Canada
The FDA approved use of the canola name in
January 1985, and U.S. farmers started planting large areas that
spring. Canola oil is lower in saturated fats, and higher in
mono-unsaturates and is a better source of omega-3 fats than
other popular oils.
Canola is very thin (unlike corn oil) and
flavorless (unlike olive oil) so it largely succeeds by
displacing soy oil, just as soy oil largely succeeded by
displacing cottonseed oil.
Page 1 of 1