C1.6 Plant oils and their uses Flashcards
Why are vegetable oils important?
- Important as foods and fuels
- Provide a lot of energy
- Provide us with nutrients
Why are saturated fats less healthy?
They increase the amount of cholesterol in the blood.
This increases the risk of heart disease.
why are unsaturated fats more healthy?
They reduce the amount of cholesterol in the blood.
Why do we use vegetable oils in cooking?
They have higher boiling points than water so can be used to cook foods at higher temperatures than by boiling.- quicker cooking.
Different flavours
Increases the energy that food releases when it is eaten
What are emulsions made up of?
droplets of one liquid suspended into another
What are emulsions thicker than?
Water or oil.
What do emulsifiers do?
help oil and water to mix
What do emulsifiers provide?
Better texture, coating ability and appearance
eg- salad dressings, ice creams, cosmetics and paints.
Describe the structure of an emulsifier
Half of the molecule is hydrophilic (attracted to water)
Half of the molecule is hydrophobic (attracted to oil)
Describe what happens to an emulsion when an emulsifier is added
The oil forms droplets, surrounded by a coating of emulsifier (with the hydrophilic part facing outwards)
Other oil droplets are repelled by the hydrophilic part of the emulsifier, while water molecules latch on
So the emulsion will not separate out
What are some benefits of using emulsifiers in foods?
- gives a LONGER SHELF LIFE
- BETTER TEXTURE
What is a down side in using emulsifiers in food?
some people are allergic to certain emulsifiers - eg egg yolk
What happens when vegetable oils ,which are unsaturated , react with bromine water?
Turn bromine water from orange to COLOURLESS
Why do unsaturated vegetable oils turn bromine water from orange to colourless?
As they are unsaturated, they contain double carbon-carbon bonds. These bonds open up and form bonds with the bromine.
How can vegetable oils that are unsaturated be hardened?
HYDROGENATION
reacting them with HYDROGEN in the presence of a NICKEL CATALYST at about 60 degrees
hydrogen adds to the carbon-carbon double bond. Turns it into an alkane
Why are hydrogenated oils useful?
- higher melting points, solid at room temperature
- So useful as spreads and in cakes and pastries
How is oil extracted from seeds and fruits?
The plant material is crushed and the oil is removed by pressing or in some cases by distillation. Water and other impurities are removed.
Describe how harding olive oil makes it less healthy
hardening involves the use of hydrogen
hydrogen reduces the number of carbon-carbon double bonds
therefore, there will be more saturated fat
Explain how emulsifier molecules are able to produce a stable mixture after shaking olive oil and water
shaking breaks up oil into tiny droplets that are unable to join up.
emulsifiers have a ‘head’ which is attracted to water - hydrophilic
and the ‘tail’ part of the emulsifier is attracted to the oil- hydrophobic
This stops the oil and water from separating out
Why does a mixture of oil and water separate?
as oil does not dissolve in water
What is the test and result for unsaturated fats?
adding bromine water
bromine water will turn from orange to colourless
Explain why hardening oils with hydrogen makes them less healthy
hydrogen reduces the number of carbon-carbon double bonds
so there will be more saturated fat
State the 2 main stages used to extract a sample of vegetable oil from seeds
crushing
distillation
Explain how a property of vegetable oil gives the oil an advantage over water for cooking foods
vegetable oils have a higher boiling point
so foods are cooked faster
Explain how emulsifier molecules are able to produce an emulsion that is a stable mixture containing oil and water
emulsifier molecules have a ‘head’ - hydrophilic- attracted to water
‘tail’- hydrophobic- attracted to oil
so forms a stable suspension as droplets repel each other
