C1.6 Plant oils and their uses Flashcards
What are oils removed from?
- Nuts
- Seeds
- Fruit
Give three examples of oils extracted from plant material
- Rapeseed oil
- Olive oil
- Lavender oil
How are oils extracted from plants?
- The plant material is crushed
- Oil is removed by pressing
- Distillation removes water, solvents and impurities
Why are vegetable oils useful in food?
- They provide a lot of energy
- They provide nutrients e.g vitamin E
- They contain essential fatty acids for metabolic processes
Why are vegetable oils useful in cooking?
- 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
Why are vegetable oils useful as fuels?
They provide a high amount of energy
What do unsaturated oils contain (in terms of their bonds)?
They contain double bonds between some of the carbon atoms in their carbon chains
What is the difference between monounsaturated oils and polyunsaturated oils?
- Monounsaturated = one C=C double bond
- Polyunsaturated = more than one C=C double bond
How can bromine water be used to test if an oil is saturated or not?
Unsaturated oils will decolourise bromine water
Explain how vegetable oils can be hardened with hydrogenation.
- By reacting them with hydrogen
- In the presence of a nickel catalyst
- At around 60 degrees c
What happens in hydrogenation in terms of bonds?
The hydrogen reacts with the double bonded carbons and opens up the double bonds
Why are hydrogenated oils more useful?
They have higher melting points than unsaturated oils and so are more solid at room temperature, making them useful as spreads and for baking
Why is margarine only a partially hydrogenated oil?
Full hydrogenation would make it too hard and difficult to spread
Why are partially hydrogenated oils often used instead of butter in processed foods?
- They are cheaper
- They keep longer
How do vegetable oils in food affect health?
- 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
What is the rule for oils and water?
They don’t dissolve in each other
What is an emulsion?
Lots of droplets of one liquid suspended another liquid
What are the differences between emulsions and oil/water?
- Thicker
- Better texture
- Better coating ability
- Better appearance
Give 4 uses of emulsions.
- Salad dressings
- Ice creams
- Cosmetics
- Paints
What are emulsifiers used for?
To make sure the oil and water mixture does not separate out
What property does the head of an emulsifier have?
It is hydrophilic
What property does the tail of an emulsifier have?
It is hydrophobic
Explain how emulsifiers work to ensure oil and water does not separate
- 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
What are the advantages to emulsifiers?
- Gives emulsions a longer shelf-life
- Food can be lower in fat but still have a good texture
