C1.6 Plant oils and their uses

Question 1

Why are vegetable oils important?

Answer 1

• Important as foods and fuels
• Provide a lot of energy
• Provide us with nutrients

Question 2

Why are saturated fats less healthy?

Answer 2

They increase the amount of cholesterol in the blood.

This increases the risk of heart disease.

Question 3

why are unsaturated fats more healthy?

Answer 3

They reduce the amount of cholesterol in the blood.

Question 4

Why do we use vegetable oils in cooking?

Answer 4

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

Question 5

What are emulsions made up of?

Answer 5

droplets of one liquid suspended into another

Question 6

What are emulsions thicker than?

Answer 6

Water or oil.

Question 7

What do emulsifiers do?

Answer 7

help oil and water to mix

Question 8

What do emulsifiers provide?

Answer 8

Better texture, coating ability and appearance

eg- salad dressings, ice creams, cosmetics and paints.

Question 9

Describe the structure of an emulsifier

Answer 9

Half of the molecule is hydrophilic (attracted to water)

Half of the molecule is hydrophobic (attracted to oil)

Question 10

Describe what happens to an emulsion when an emulsifier is added

Answer 10

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

Question 11

What are some benefits of using emulsifiers in foods?

Answer 11

• gives a LONGER SHELF LIFE

- BETTER TEXTURE

Question 12

What is a down side in using emulsifiers in food?

Answer 12

some people are allergic to certain emulsifiers - eg egg yolk

Question 13

What happens when vegetable oils ,which are unsaturated , react with bromine water?

Answer 13

Turn bromine water from orange to COLOURLESS

Question 14

Why do unsaturated vegetable oils turn bromine water from orange to colourless?

Answer 14

As they are unsaturated, they contain double carbon-carbon bonds. These bonds open up and form bonds with the bromine.

Question 15

How can vegetable oils that are unsaturated be hardened?

Answer 15

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

Question 16

Why are hydrogenated oils useful?

Answer 16

• higher melting points, solid at room temperature

- So useful as spreads and in cakes and pastries

Question 17

How is oil extracted from seeds and fruits?

Answer 17

The plant material is crushed and the oil is removed by pressing or in some cases by distillation. Water and other impurities are removed.

Question 18

Describe how harding olive oil makes it less healthy

Answer 18

hardening involves the use of hydrogen

hydrogen reduces the number of carbon-carbon double bonds

therefore, there will be more saturated fat

Question 19

Explain how emulsifier molecules are able to produce a stable mixture after shaking olive oil and water

Answer 19

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

Question 20

Why does a mixture of oil and water separate?

Answer 20

as oil does not dissolve in water

Question 21

What is the test and result for unsaturated fats?

Answer 21

adding bromine water

bromine water will turn from orange to colourless

Question 22

Explain why hardening oils with hydrogen makes them less healthy

Answer 22

hydrogen reduces the number of carbon-carbon double bonds

so there will be more saturated fat

Question 23

State the 2 main stages used to extract a sample of vegetable oil from seeds

Answer 23

crushing

distillation

Question 24

Explain how a property of vegetable oil gives the oil an advantage over water for cooking foods

Answer 24

vegetable oils have a higher boiling point

so foods are cooked faster

Question 25

Explain how emulsifier molecules are able to produce an emulsion that is a stable mixture containing oil and water

Answer 25

emulsifier molecules have a ‘head’ - hydrophilic- attracted to water

‘tail’- hydrophobic- attracted to oil

so forms a stable suspension as droplets repel each other