Plant Oils
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Plant Oils
Learning Objectives:
1.Describe how plant oils are extracted.
2.Explain the differences between saturated
and unsaturated fats.
3.Evaluate the impacts of using vegetable oils
in food.
4.Describe how to make margarine from
vegetable oil.
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Where can we find plant oils?
Oils are naturally found in plants, particularly in their
fruits, nuts and seeds. They are used in many foods and
are an important source of nutrients, but they can also be
used as fuel, for example, in biodiesel.
The oils can be extracted by
crushing the plant material to make
a paste, which is then pressed to
remove the oils. Oils obtained in
this way are often called virgin oils.
Sometimes distillation is needed to
remove water and other impurities
from the plant oils. These oils may
be labelled as refined oils.
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Extracting Plant Oils
• Pressing
• Solvent extraction
• Steam Distillation
Pressing (Olive Oil)
1. Crush into paste
2. Mix paste for 30 minutes (oil
drops combine)
3. Traditional: Press paste
between fibre mats and
liquid is squeezed out
(Modern: spin in centrifuge)
4. Let liquid sit, oil and water
separate
5. Let oil settle in stainless
steel tanks for at least one
month (impurities settle out)
Solvent Extraction (Sunflower oil)
• Press the seeds
• Add a solvent (such
as hexane) which will
dissolve the oils and
remove them from
the solids
• Use distillation to
separate the oil from
the solvent.
Steam Distillation (Lavender Oil)
1. Heat mixture
until it boils.
2. Steam and plant
oil vapour move
to the
condenser.
3. Gases cool and
turn to liquid.
4. Oil and water is
collected.
5. Oil floats on top.
Types of plant oils
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Testing oils
The level of unsaturation in an oil can be detected using a
dilute solution of bromine (Br2), an element which reacts
with carbon–carbon double bonds.
The bromine water is added to
the oil and the mixture shaken.
colourless = unsaturated oil
remains red = saturated oil.
The more bromine that is needed before the solution stays
red, the more carbon–carbon double bonds there are in the
oil, and the more unsaturated it is.
Bromine test for unsaturated oils
• Add bromine water
(reddish brown)
• Turns colourless if
unsaturated oils
present (alkenes)
alkane
alkene
saturated unsaturated
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Cooking using plant oils
Plant oils have higher boiling points than water.
Can be used to cook food more quickly.
Cooking in oil can give food a different texture and flavour.
Health Concerns
• Cooking in oil also increases the energy
that the food releases when it is eaten.
• Consumption of more energy than you
need can lead to weight gain and heart
disease.
• Saturated fats (animal fats) raise blood
cholesterol.
• Unsaturated fats (plant oils) are better for
your health.
Plant oils and health
Eating too many saturated oils can lead
to health problems.
But consuming unsaturated oils can help
lower cholesterol and provide the body
with essential fatty acids (EFAs).
Omega 3 is an EFA found in oily fish, avocados and certain
oils, including flaxseed oil, which may help to protect against
heart disease. Some people believe that omega 3 fatty acids
can improve children’s ability to learn.
Many people in the UK eat too many foods
containing saturated fats and oils, and not
enough containing unsaturated fats and oils.
Hardening Oils (Margarine)
• Unsaturated fats are
liquid are room
temperature (they have
lower melting pts).
• Can be hardened by
hydrogenation this
turns them into
saturated fats.
Hydrogenation
1. Add hydrogen gas to unsaturated fat.
2. Using a nickel catalyst.
3. At 60 oC.
unsaturated
saturated
Did you get all that?
1. What are plant oils used for?
2. What are the different methods of extracting plant oils? How do they
work?
3. What are the different types of fatty acids in oils? How are they
different?
4. What do the terms saturated and unsaturated mean?
5. How do you test for unsaturated fats? How does this work?
6. Why are oils useful in cooking? Why do foods fried in oil turn our
crispy?
7. What type of fats are unhealthy and which are healthier for you?
Where are these found?
8. What are some potential health concerns of eating too much “bad”
fat?
9. What are some potential health benefits of eating “good” fats?
10. How do you make margarine? What is this process called? How
does it work? What properties have changed?