Plant oils and Emulsifiers

Question 1

What are vegetable oils obtained from?

Answer 1

Plants.

Question 2

What can vegetable oils be used for?

Answer 2

Fuel and making foods.

Question 3

What are emulsifiers?

Answer 3

Food additives that stop water mixtures in food and oils from separating.

Question 4

How are oils extracted?

Answer 4

Nuts, seeds and some fruits are crushed and pressed to squeeze the oil out.

Question 5

What happens if oils cannot be extracted through crushing and pressing?

Answer 5

The oil needs to be dissolved in a solvent. Once the oil is dissolved, the solvent is removed through distillation.

Question 6

What do molecules of vegetables consist of?

Answer 6

Glycerol and fatty acids.

Question 7

How are vegetables oils different to water?

Answer 7

They have a higher boiling point.

Question 8

What does it mean if one substance has a higher boiling point than another?

Answer 8

It means that foods can be cooked or fried at higher temperatures than they can be cooked or boiled in water.

Question 9

Explain saturated fatty acids.

Answer 9

They only have single bonds between their carbon atoms. Saturated oils tend to be solid at room temperature and sometimes tend to be called vegetable fats instead of vegetable oils.

Question 10

Explain unsaturated fatty acids.

Answer 10

They have double bonds between their carbon atoms. Unsaturated oils tend to be liquid at room temperature. Unsaturated oils are divided into two categories:
Monounsaturated fats have one double bond for each fatty acid.
Polyunsaturated fats have many double bonds.
Unsaturated fats are better for a healthy diet than saturated fats.

Question 11

What happens during an emulsion?

Answer 11

When an oil and water are shaken together tiny droplets of one liquid starts to spread throughout the other. This forms a mixture called an emulsion.

Question 12

Why are emulsions more useful in foods than the oil and water they contain?

Answer 12

Because they are more viscous (thicker).

Question 13

What happens if an emulsion is left to stand?

Answer 13

A thin layer of oil will begin to form on the top of the surface.

Question 14

What are the two different ends of an emulsifier?

Answer 14

A hydrophilic end (‘water-loving’) - this forms bonds with the water molecules but not the oils.
A hydrophobic end (‘water hating’) - this forms bonds with the oil molecules but not the water.

Question 15

What do unsaturated vegetable oils contain?

Answer 15

Double carbon-carbon bonds.

Question 16

How can unsaturated vegetable oils be detected with bromine water?

Answer 16

Bromine water becomes colourless when shaken with an unsaturated vegetable oil but stays an orange-brown when shaken with a saturated vegetable oil.

Question 17

What is bromine water useful for?

Answer 17

Determining the amount of unsaturation of a vegetable oil.

Question 18

What is hydrogenation?

Answer 18

When unsaturated vegetable oils are hardened by reacting with hydrogen.

Question 19

What happens during hydrogenation?

Answer 19

Vegetable oils are reacted with hydrogen at around 60 degrees Celsius. A nickel catalyst is used to speed up the reaction. The double bonds are converted to single bonds in the reaction. In this way unsaturated fats can be made into saturated fats – they are hardened.