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Vegetable Oils
Plants convert sunlight into glucose by photosynthesis.
Some of the glucose is turned into plant oils.
These oils can be extracted from the plants by
­ Pressing
­ Steam Distillation
­ Cold solvent extraction
Many plant oils contain carbon ­ carbon double bonds
and are said to be unsaturated.
These double bonds will turn bromine water colourless
and the more double bonds in an oil (polyunsaturated) the
more bromine water that can be decolourised.
Iodine solution will also react with double bonds and its
colour will change from red/brown to colourless…read more

Slide 2

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Vegetable Oils
Vegetable oils are a very concentrated source of energy.
Food is cooked in vegetable oils because they have a
much higher boiling point than water and so the food
cooks more quickly and its outside is made crispy.
However the food absorbs some of the oil so it is more
calorific.
Vegetable oils are used as a replacement for animal fats
but they can be less useful as they are liquid. These
vegetable oils can be hydrogenated which results in them
having higher melting points and so be more solid at
room temperature. These are called hydrogenated
vegetable oils and are used in biscuit manufacture.
However the process can produce trans fatty acids, which
may cause health problems.…read more

Slide 3

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Vegetable Oils
The following is an extract from Nutritional
Information labels on oils sold by Tesco
Vegetable Olive Oil Sunflower Sesame Oil
Oil Oil
Fats (g)
100 100 100 100
Of which saturates
(g) 7.0 14.3 12.0 16.0
Monounsaturates (g)
61.0 73.0 23.0 40.0
Polyunsaturates (g)
31.0 8.2 65.0 44.0…read more

Slide 4

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Biofuels
Vegetable oils can be processed to make a fuel which has
similar properties to diesel, called Biodiesel.
Biodiesel is not a fossil fuel and so, in theory, is Carbon
Neutral.
Bioethanol is a substitute for petrol and is made from
cereals. The starch is hydrolysed to glucose and this is
fermented to form ethanol solution which is distilled to
give pure ethanol.
There is a conflict of interest between growing cereals for
food or fuel and this has pushed up the price of foods this
year as there is only a limited amount of arable land
available.…read more

Slide 5

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Emulsions
An emulsion is formed when small droplets of an oil are
dispersed through water.
To ensure that they stay separate chemicals are added
which are called emulsifying agents or emulsifiers.
Many of our foods are emulsions eg mayonnaise, ice
cream, milk…read more

Slide 6

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Vegetable oils as
fuels
C1b 5.5
How can we use vegetable
oils as a fuel?
© Cummins
Racing…read more

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