C1.6 Plant oils and their uses

Question 1

What are oils removed from?

Answer 1

• Nuts
• Seeds
• Fruit

Question 2

Give three examples of oils extracted from plant material

Answer 2

• Rapeseed oil
• Olive oil
• Lavender oil

Question 3

How are oils extracted from plants?

Answer 3

• The plant material is crushed
• Oil is removed by pressing
• Distillation removes water, solvents and impurities

Question 4

Why are vegetable oils useful in food?

Answer 4

• They provide a lot of energy
• They provide nutrients e.g vitamin E
• They contain essential fatty acids for metabolic processes

Question 5

Why are vegetable oils useful in cooking?

Answer 5

• They have a higher boiling point than water so they can be used to cook foods at higher temperatures and at faster speeds
• They also give food a different flavour by releasing chemicals from food soluble in oil
• They increase the amount of energy we get from food

Question 6

Why are vegetable oils useful as fuels?

Answer 6

They provide a high amount of energy

Question 7

What do unsaturated oils contain (in terms of their bonds)?

Answer 7

They contain double bonds between some of the carbon atoms in their carbon chains

Question 8

What is the difference between monounsaturated oils and polyunsaturated oils?

Answer 8

• Monounsaturated = one C=C double bond

- Polyunsaturated = more than one C=C double bond

Question 9

How can bromine water be used to test if an oil is saturated or not?

Answer 9

Unsaturated oils will decolourise bromine water

Question 10

Explain how vegetable oils can be hardened with hydrogenation.

Answer 10

• By reacting them with hydrogen
• In the presence of a nickel catalyst
• At around 60 degrees c

Question 11

What happens in hydrogenation in terms of bonds?

Answer 11

The hydrogen reacts with the double bonded carbons and opens up the double bonds

Question 12

Why are hydrogenated oils more useful?

Answer 12

They have higher melting points than unsaturated oils and so are more solid at room temperature, making them useful as spreads and for baking

Question 13

Why is margarine only a partially hydrogenated oil?

Answer 13

Full hydrogenation would make it too hard and difficult to spread

Question 14

Why are partially hydrogenated oils often used instead of butter in processed foods?

Answer 14

• They are cheaper

- They keep longer

Question 15

How do vegetable oils in food affect health?

Answer 15

• Natural unsaturated fats reduce the amount of blood cholesterol, reducing the risk heart disease
• But partially hydrogenated oils, due to “trans” fats, increase the amount of cholesterol in the blood

Question 16

What is the rule for oils and water?

Answer 16

They don’t dissolve in each other

Question 17

What is an emulsion?

Answer 17

Lots of droplets of one liquid suspended another liquid

Question 18

What are the differences between emulsions and oil/water?

Answer 18

• Thicker
• Better texture
• Better coating ability
• Better appearance

Question 19

Give 4 uses of emulsions.

Answer 19

• Salad dressings
• Ice creams
• Cosmetics
• Paints

Question 20

What are emulsifiers used for?

Answer 20

To make sure the oil and water mixture does not separate out

Question 21

What property does the head of an emulsifier have?

Answer 21

It is hydrophilic

Question 22

What property does the tail of an emulsifier have?

Answer 22

It is hydrophobic

Question 23

Explain how emulsifiers work to ensure oil and water does not separate

Answer 23

• The head latches onto the water molecules
• The tail latches onto the oil droplets
• This keeps the oil droplets separate as the heads repel them
• So the droplets cannot come together keeping the oil and water mixed in together

Question 24

What are the advantages to emulsifiers?

Answer 24

• Gives emulsions a longer shelf-life

- Food can be lower in fat but still have a good texture

Question 25

What is the disadvantage to emulsifiers?

Answer 25

Some people are allergic to certain emulsifiers