C1.6 Plant Oils and their Uses Flashcards
What natural materials can we extract oil from? (3)
Some fruits, nuts and seeds
How can we extract oil from plant material? (2)
By crushing and pressing it, or using distillation
Explain the process of using crushing and pressing to extract oil (2)
Crushed plant materials is pressed between metal plates to squeeze the oil out. A centrifuge is then used to separate the oil from any water/plant material - the oily paste made is spun around at high speeds causing the oil and water to separate
Describe the process of distillation to extract oil
The plant material is heated until the oil within it evaporates. The vapour is then collected and condensed into the liquid oil
How is the plant material in distillation heated?
Using steam, the steam is passed over the plant material to heat it
What is a benefit of using distillation over crushing and pressing?
The oil and water produced in distillation is collected in a funnel with a top on the bottom (a separating funnel), which is an easy way to separate the oil from the water
What (health) benefits are there to using plant oils in food? (3)
They have a high energy content, oils from seeds contain vitamin E and vegetable oils contain essential fatty acids
What benefits are there to using plant oils to cook? (2)
They have higher boiling points than water so they can be used to cook foods at higher temps which cooks food faster and plant oils intensifies the taste of the food being cooked
What drawbacks are there to cooking with plant oils?
They are high in energy - so eating too much cooked in plant oils makes you put on weight
Why are plant oils good to use as fuels? (3)
Because they are renewable, carbon neutral and high in energy
What are oils and fats made of?
Long-chain molecules with lots of carbon atoms
What’s the difference between saturated and unsaturated fats/oils?
Unsaturated fats/oils contain carbon-carbon double bonds
What are monounsaturated fats?
They contain one carbon-carbon double in their carbon chains
What are polyunsaturated fats?
They contain more than one carbon-carbon double in their carbon chains
What is the test for unsaturated fats/oils?
By adding the unsaturated fat/oil to bromine water, if unsaturated, the bromine water will be decolourised from orange
Unsaturated oils are liquid at room temperature, how can they be hardened?
By reacting them hydrogen in the presence of a nickel catalyst at about 60̊C - this is hydrogenation
What happens to hydrogenated oils?
They lose their double bonds, the hydrogen adds to the carbon-carbon double bonds opening them up
Why are unsaturated oils hydrogenated?
Because they have a higher melting point so they are more solid at room temp - making the spreadable e.g. margarine
How are hydrogenated oils in industry?
They are used in baking cakes and pastries as they are cheaper than butter and they keep longer - making them cheaper and gives them a longer shelf life
What happens if you continue to hydrogenate an oil?
It will contain more saturated fat and will become harder - if products like margarine were too hard, they would be difficult to spread
Are vegetable oils saturated or unsaturated?
Unsaturated
Are animals fats saturated or unsaturated?
Saturated
Why are unsaturated fats healthier than saturated fats?
Because unsaturated fats reduce the amount of cholesterol in the blood, whereas unsaturated fats increase the cholesterol in the blood and increase the risk of heart disease
What is oil mixed with water an example of?
An emulsion
What are emulsions?
Lots of droplets of one liquid suspended in another liquid
How can you make an emulsion?
Examples of emulsions are oil-in-water and water-in-oil, these are made by mixing them together and shaking them
What are the properties of emulsions?
They are thicker than the original products
What are emulsions used for in food? (5)
Salad dressing, mayonnaise, milk, whipped cream and ice cream
Besides in food, what other uses do emulsions have? (2)
Moisturising lotions and paint
What are emulsifiers?
Substances which stop the oil and water mixtures from separating
What are examples of emulsifiers? (2)
Egg yolk and lecithin
What is the structure of an emulsifier molecule?
They have a hydrophilic heads and a hydrophobic tail - the hydrophilic head latches onto water molecules and the hydrophobic tail latches onto oil molecules
How do emulsifiers work?
When water and oil is mixed with an emulsifier, the tail latches onto an oil molecule, the head then sticks out of the oil mole’ and latches onto the water making the emulsion stable so it won’t separate
What are advantages of emulsifiers? (2)
They stop emulsions from separating giving them a longer shelf life, and it allows food to be produced which is low in fat but still has a good texture
What are disadvantages to emulsifiers? (1)
Some people can be allergic to certain emulsifiers
