Oils from plants

C1.6

What do I need to know?

• Recall that oils can be obtained from plants

• Describe the properties of oils and formation of emulsions

• Explain why saturated fats are solid and unsaturated fats are liquids

Vegetable oils

• Oils can be extracted from fruits, seeds, flowers and nuts.

• The plant material is crushed and the oil removed by pressing or steam distillation.

• Water and other impurities are then removed.

Vegetable oils

• Vegetable oils are important fuels and foods and they provide us with energy and nutrients.

Cooking with vegetable oil

• Vegetable oils have higher boiling points than water.

• This means they can be used to cook food more quickly than boiling.

• This also increases the energy the food releases when it is eaten.

Emulsions

• Oils do not dissolve in water.

• This is because they FLOAT

• Oils can be used to make emulsions – these are thicker than water and have useful properties.

What do we use emulsions for?

• Emulsions are good for coating surfaces eg paint and cosmetics.

• They have an appealing texture in food eg ice cream and mayonnaise

Oil and water?

• What will happen to a mixture of oil and water over time?

• It will separate

Emulsifiers

• Emulsifiers keep the product in an emulsion and stop it separating out

• Emulsifiers are molecules that have one part that is attracted to water and one that is attracted to oil.

• An example is washing up liquid.

Emulsifiers

• Emulsifiers have a head that is attracted to water and a tail that is attracted to the oil.

Unsaturated oils

• Unsaturated fats like olive oil have double bonds and decolorize bromine water.

• When making margarine hydrogen is passed through the oil in the presence of a nickel catalyst at 60°C

• This fills up the molecule with hydrogen making it a solid fat.