Oils and fats
David S. Seigler
Department of Plant Biology
University of Illinois
Urbana, Illinois 61801 USA
seigler@life.illinois.edu
http://www.life.illinois.edu/seigler
OUTLINE: OILS AND FATS
Importance
o All cultures
o Required in diet
Botanical
o Many families
Economics
o Multiple plant use
o Press-cake
Chemistry
o Triglycerides
o Short vs long chain fatty acids
o Unsaturated vs saturated fatty acids
o Soaps-saponification
o Polymerization - paints
+ Non-drying
+ Drying
+ Semi-drying
o Precursors for plastics
o Petroleum substitute
Isolation
o Extraction methods
o Crushing/expression
Reading
• CHAPTER 9 IN THE TEXT
Introduction
• Oils (liquid) and fats (solid) common
and important items in the diet of
humans.
• Most of the ones we use come from
seeds (or animals).
• The use of seed oils is ancient.
• In contrast to essential oils, these substances
are made up of triglycerides and are not
volatile.
• Triglycerides contain fatty acids and glycerol.
• The structures of the fatty acids determine
many of the properties of the oils and fats.
• Triglycerides are a food reserve for the
germinating embryo.
• Similar oils and fats are obtained from
animals.
• In general, the longer the chains of the
fatty acids, the higher boiling the oils or
fats are.
• Peanut oil has lots of C20 fatty acids and
is high boiling.
• Sites of unsaturation lower the boiling point
and increase the sensitivity to oxygen.
• The oils with 2 or 3 sites of unsaturation
polymerize readily and have often been used
in paints.
• The properties of highly unsaturated oils
that make them valuable also make
them undesirable for food products
because they tend to turn rancid readily.
• Unsaturated oils can be converted to
saturated oils by hydrogenation with a
catalyst (usually nickel). This raises the
melting point.
• Originally done by Wesson. Pg. 221.
• Non-drying-saturated- typically tropical plants
palm, peanut, olive, rape, castor, almond
• Drying oils-highly unsaturated
(polyunsaturated) linseed, tung, soy bean,
hempseed, nut, poppy, safflower
• Semi-drying oils (moderately unsaturated)
cottonseed, sunflower, sesame, croton, corn.
• Many important oils are listed on page 230231.
• Many seeds contain quite large quantities of
oils. Sesame seed, for example, is more than
half oil.
Extraction methods
• The seeds are usually cleaned and then
dehusked.
• Crushing - today done mostly with rollers. A screw
press makes it possible to have a continuous
feeding of seeds. The oil flows out (pg. 229, 227).
• Because there is still 2-4% oil in the meal, the
material is extracted again with solvents in some
cases.
• In some cases, the kernels are broken or flaked
before extraction.
• Expression - cold and hot (where seeds
are cooked first). For an outline of the
complete process, see pg. 229.
• Extraction - solvents (petroleum ether
(hexane), chlorinated solvents).
• Boiling - centrifugation
Subsequent treatment of oils
• After isolation, the oils are treated for several
reasons.
• In many cases, the oils are treated with
caustic soda to remove any free fatty acids
present.
• The oil may then be degummed, bleached,
deodorized, and/or winterized.
• Degumming is done by mixing the oil with
water and centrifuging.
• Bleaching is usually done with Fuller's earth
or activated charcoal.
• Deodorizing is often done with steam.
• Winterizing is cooling down the oil and
removing materials that precipitate out.
• The fatty acids and triglycerides that
precipitate out are called "foots".
• Most oils are treated to render them odorless
and tasteless (and interchangeable).
Uses of fats and oils
• Almost all oils and fats come from seeds
(except for olive and avocado). They are
required in the diet of most animals.
• Margarine and shortening are made by
hydrogenation.
• Lubricants
• Soap - now largely replaced by
synthetic detergents
• Paints - now largely replaced by
synthetic polymers.
• Chemical precursors - nylon, polymers probably the best petroleum substitute.
• Press cake is usually used for livestock
feed
• Biofuels
Major oilseed crops
• Table pages 230-231.
• Linseed oil
• This is probably the oldest domesticated oil
seed crop. Flax or linseed (Linum
usitatissimum, Linaceae) is from the Near
Eastern Center. Fossil linseed shows signs of
selection by 6000 B.C.
• In the time of the Egyptians, coffins were
painted with mixtures of linseed oil and resin.
• The plant is also used for fiber.
• Linseed oil alone still used to finish
many wood products. Linseed oil is
used as an edible oil in some parts of
the world, but has largely been replaced
by other oils.
• Flax seed a major source of omega-3fatty acids and may be valuable in
human diets.
Flax in the Pampas of Argentina
Flax, Linum usitatissimum, Linaceae
Tung oil, Aleurites fordii, Euphorbiaceae
• Tung oil is mostly from China.
• This small tree has fruits that contain a
highly unsaturated but inedible oil.
• Tung oil one of the best quality furniture
finishing oils.
• The press cake is highly toxic.
Tung, Aleurites fordii,
Euphorbiaceae
Safflower oil, Carthamus tinctorius, Asteraceae
or Compositae
• Safflower oil is unsaturated and is considered
to be a good quality salad oil.
• Safflower was domesticated in the
Mediterranean area. This species is only
known in cultivation.
• Safflower was probably first grown for the
yellow dye it produces.
Safflower, Carthamus tinctorius, Asteraceae
Soybeans (Glycine max)
• Soybeans are, of course, an ancient crop as
previously described.
• In the Orient they are not usually used for oil
purposes. Europeans began to press them
back in the 1700's.
• Today, almost all soybeans used in the U.S.
are pressed for oil. The soybean is about 1325% oil.
• The press cake is used for feeding livestock
and as a human food additive.
Glycine max, soybean
Soybean harvest
soybeans
Sunflower (Helianthus annuus)
Asteraceae
• The sunflower was domesticated about 5000
years ago in Mexico and has become a major
crop.
• The seeds were widely eaten by the
American Indians.
• The crop was highly modified in Europe,
however. It is an especially an important crop
in the former Soviet Union.
Sunflowers,
Helianthus annuus,
Asteraceae
• The cultivated types of sunflowers today
are much larger than the wild ones. The
plant is still a common weedy species in
much of the Midwest.
• See sunflower diagram on pg. 234.
Corn or maize (Zea mays)
• Corn, of course, is cultivated for other
purposes, but also for oil. The oil is a minor
by-product of corn milling to isolate starch.
The corn is steeped in sulfurous acid and
then lightly macerated to separate the
embryo from the endosperm.
• Diagram pg. 235.
• The oil is isolated from the embryos. Most
refined corn oil used for margarine and salad
oils.
Male and female corn structures
Carolina Biological Supply Co.
Sesame (Sesamum indicum, Pedaliaceae)
• Sesame oil an ancient crop. It probably arose
in India.
• On the other hand, the close relatives of
sesame are mostly from Africa.
• The oil has a relatively strong flavor and is
much used in Chinese cooking.
• Sesame oil commonly used in Africa, the
Middle East, India, and China.
• The seeds themselves are also widely eaten.
Sesame, Sesamum indicum, Pedaliaceae
Courtesy Dr. Dorothea Bedigian
Courtesy Dr. Dorothea Bedigian
Sesame seed
Cotton (Gossypium hirsutum, Malvaceae)
• Cotton widely grown for fiber.
• The seeds used as a source of edible oil for
thousands of years.
• Cotton seed contains a toxic compound,
gossypol. A problem in utilizing the press
cake.
• David Wesson's process of purification with
caustic soda, steam and fuller's earth
removed much of the gossypol.
• Shortening was first made by hydrogenation
of cottonseed oil.
Cotton, Gossypium hirsitum, Malvaceae
Cotton field and cotton boll
Rape or canola, Brassica napus,
Brassicaceae or Cruciferae
• Rapeseed or canola commonly grown in
Canada and in Europe.
• The oil used for both a lubricant and as an
edible oil. It is largely used to make
margarine in Europe.
• Selection for low erucic acid lines (canola) for
edible purposes and cultivation of erucic acid
lines for lubricant purposes.
• The press cake of limited value for feeding
livestock.
Canola, Brassica napus, Brassicaceae or
Cruciferae, in Ontario
Courtesy Dr. Clint Chapple
Flax and canola in Manitoba
Courtesy Dr. Ellis McLeod
Rapeseed in Germany
Peanut oil, Arachis hypogaea, Fabaceae or
Leguminosae
• Peanut oil widely used in the tropics.
• It is especially common in Africa and in
France.
• Peanut oil higher boiling than most other oils
and imparts a pleasant taste to the food.
Arachis hypogaea, peanut in flower
Pollinated ovary going under the soil
Primitive peanut relative - Arachis villosa
Olive oil (Olea europaea, Oleaceae)
• Olive oil is another ancient crop from the
Near East. At least 3500 B.C. in Crete.
• Olive oil was also used as a cleanser, for
annointing, as a lamp oil, for medicine, and
as a food stuff.
• Olive oil comes from both the fruit pulp and
from the seed.
• There are many different grades of olive oil.
Olives, Olea europaea,
Oleaceae
Castor bean (Ricinus communis,
Euphorbiaceae)
• Castor bean probably grew in both Asia and
Africa when it was domesticated.
• Seeds at least 6000 years old have been
found in Egyptian tombs.
• The oil was probably used in medicine and as
a lamp oil.
• Castor oil is also a precursor for plastics.
Castor bean
(Ricinus communis,
Euphorbiaceae)
Castor bean
(Ricinus communis,
Euphorbiaceae)
• Castor oil is still used as a laxative. The
seeds are highly toxic but the compounds
responsible are not soluble in the oil. Pg.
239.
• Today most castor oil is used for soaps,
paints, and Turkey red oil. It is also used
widely as a lubricant.
• The press cake is too toxic for any use except
fertilizer.
Palm and palm kernel oils
• Oil palms (Elaeis guineensis, Arecaceae)
differ from most other oil seeds in that both
the fruit pulp and the seed are used.
• Actually a series of palms are used. Another
one is Oribignya oleifera (native to S.
America). There is also a comparable Asian
species.
African oil palm (Elaeis guineensis,
Arecaceae)
National Geographic
• The African oil palm is probably the most
widely cultivated today.
• Pg. 240. The plant is only semicultivated. The
fruits are harvested when ripe.
• Most consumers in isolated, rural areas make
their own oil by boiling the fruits and collect
the oil as it floats to the top.
• Commercially, the fruits are pressed quickly
after cooking with steam. The kernels are
extracted later.
• Palm oils are used for soap and candles, but
also in margarine and for shortening.
Cooking dende oil from
oil palms
Courtesy Axel Walther
Coconuts (Cocos nucifera, Arecaceae)
• Coconut oil is isolated from copra, the “meat”
that is removed from the seeds and dried.
Coconuts are widely used in the tropics for
just about everything.
• Coconuts originated in southeastern Asia.
• In the 1800's, people started to use coconut
oils to make soap.
• Coconut oil also mixes with many other oils
and has a pleasant taste.
Coconuts (Cocos nucifera,
Arecaceae)
Extracting copra from coconuts in Oceania
Courtesy Dr. S. Glassman
• The press cake also used as a cattle
feed.
• Coconut oil used in shampoos, hand
lotions, suntan creams, non-dairy
products, cosmetics.
Other oilseeds
• In some countries, crambe (Crambe
abyssinica, Brassicaceae or Cruciferae) is
used. It is similar to rape seed oil.
• Grapeseed oil (Vitis vinifera, Vitaceae) is
used in countries where grapes are
commonly grown for wine making.
• Hempseed oil (Cannabis sativa,
Cannabaceae) oil is used in some Near
Eastern countries.
Niger seed, Guizotia abyssinica,
Asteraceae
Shea butter tree,
Butyrospermum parkii,
Sapotaceae
The fats from the fruits are
used as a food in West Africa
and in cosmetics worldwide
Soap
• Soaps are the salts of fatty acids. Potassium
and sodium soaps are the most commonly
used.
• Magnesium and calcium soaps are found as
bathtub ring.
• Lead and zinc are used to make medicinal
soaps
• Lithium soaps are used to make lubricants.
• Aluminum soaps are used for waterproofing.
Device for isolating “caustic” potassium carbonate from wood ashes
• Oils and fats are treated with lye (sodium
hydroxide or potassium hydroxide) to yield
salt of the fatty acids. Formerly, extracts of
wood ashes were used. Potassium gives soft
soaps and sodium gives hard soaps.
• Detergents often made by sulfonation of other
types of organic molecules.
• Saponins from plants used in some societies
as soap or detergent substitutes.
• Coconut oil is still the most commonly used
oil for soap.
Paints
• Many polyunsaturated oils are incorporated
with pigments into paints and varnishes.
• Linseed oil and tung are among the most
common of this type.
• The Flemish combined pigments and oils to
make oil paints in the 15th century. They
perfected technique of painting over the
pictures with glazing, and translucent
coatings over an undercoating in order to give
an illusion of depth.
• Pg. 223.
• Vegetable oils are heated with heavy
metal salts to catalyze polymerization
before being used in paints. These help
the oil to absorb oxygen.
• Varnishes also include resins.
• In general, today, people have shifted to
water-based paints.