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Vegetable Oils.
What are Vegetable Oils?
Vegetable oils come from many
plants. Examples
are lavender, olive,
palm, rapeseed and sunflower.
The oils contain a lot of energy
and are used as food
(in cooking - see below, or making emulsions)
or
for making fuels (for example biodiesel).
How are Vegetable Oils Extracted?
It is usually the seeds (or
nuts) of a plant that
contain
the most oil.
The oil is extracted by
crushing the
seeds and
then squeezing the crushed material (called
pressing).
Some oils are extracted by distillation.
The oil can then be
refined (made
purer)
by removing water and other
impurities.
Why are Vegetable Oils used
in Cooking?
Vegetable oils used in
cooking have a higher
boiling point
than water
which boils at
100 °C.
Cooking food at a
higher temperature is quicker
and produces different flavours.
The cooked food usually has more energy
because
some of the oil remains on the food after
cooking and some of
the water in the cells of the
food becomes replaced by oil.
Eating too much food cooked in oil can make you
overweight.
This happens if the oily food that you eat has more
energy
in it than the amount of energy that you use during
exercise.
Are Vegetable Oils Healthy
to Eat?
Some vegetable oils are
better for your health
than others.
Oils containing many unsaturated
fats are more
healthy than oils with a large proportion of saturated
fats.
Unsaturated means that the molecule
contains
one or more double
bonds between carbon atoms.
Saturated means that the molecule has no double
bonds.
Bromine water can be used to see if
a substance
such as an oil or other compound has double bonds.
Palm oil is more saturated and
sunflower oil is
more unsaturated.
Olive oil and rapeseed oil are somewhere in between.
It is possible to make an oil more saturated to make
margarine.
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