How can vegetable oils be extracted from plants?
Vegetable oils can be extracted from plants by pressing or by distillation.
Why are vegetable oils important?
Vegetable oils provide nutrients and have a high energy content. They are important foods and can be used to make biofuels.
Extracting lavender oil from lavender plants:
• Extracted by the process of distillation • The plants are put into water and boiled • The oil and water evaporate together and are collected by condensing them • The water and other impurities are removed to give pure lavender oil
What do unsaturated oils contain?
Unsaturated oils contain carbon-carbon double bonds (C=C).
How can the double bond in unsaturated oils be detected?
We can detect the double bonds in unsaturated oils with bromine water. Unsaturated oil + bromine water (orange) -> colourless solution
Why are vegetable oils useful in cooking?
They have a high boiling point.
Why do we use vegetable oils in cooking?
• Vegetable oils are used as the food cooks more quickly • The outside of the food changes colour and turns crispier • The inside of the food is much softer
What is a problem with using vegetable oils?
Vegetable oils have a high energy content so they could potentially be unhealthy if regularly eaten.
Hardening unsaturated oils:
• Unsaturated oils are usually liquids at room temperature • The boiling and melting points of these oils can be increased by adding hydrogen to the molecules • Carbon-Carbon double bonds are replaced with Carbon-Carbon single bonds • The vegetable is hardened by reacting it with hydrogen gas. To make the reaction occur, we must use a NICKEL catalyst and carry the process out at around 60 degrees C
Uses of hardened oils:
Oils that have undergone the hardening process are called hydrogenated oils. They are solids at room temperature so they can be made into spreads to be put on bread. They can also be used to make cakes, biscuits and pastry.
What do emulsifiers do?
Emulsifiers stop oil and water from separating into layers.
How does an emulsifier work?
An emulsifier works because the tail of its molecule dissolves in oil (hydrophobic part) and the head dissolves in water (hydrophilic part). This keeps them spread throughout the water, stopping the oil and water from separating out into two layers.
What are emulsions made from vegetable oils used in?
These emulsions are used in many foods, such as salad dressings, ice creams, cosmetics and paints.
Ice creams and emulsifiers:
Emulsifiers keep the oil and water mixed together in the ice cream while we freeze it. Without them, the water in the ice cream freezes separately and produces crystals of ice. This happens if you allow the ice cream to melt and then put it back in the freezer.
What is a food additive?
A food additive is a substance added to food to preserve it or improve its taste, texture or appearance. E numbers are additives which have been approved and added to foods in Europe.
What do emulsifiers do to the texture of foods?
Emulsifiers make fatty foods more palatable and tempting to eat.