C1.6 Plant oils and their uses Flashcards
How are oils extracted from plants?
The plants are crushed and the oil removed through pressing or distillation
How is oil separated from crushed plant material?
By a centrifuge or solvents
What does distillation do to the oil extracted from plants?
It removes water, solvents and impurities
Examples of fruits rich in oil
Avocados and olives
Examples of seeds rich in oil
Brazil nut, peanuts and sesame seeds
What can plant oils be used for?
Food or for fuel
What is the traditional method of producing olive oil?
The olive is crushed. The crushed olive is then pressed between metal plates and the oil is squashed out
Vegetable oils provide a lot of
Energy
Oil from seeds contain
Vitamin E
Vegetable oils contain essential
Fatty acids
Why are vegetable oils good for cooking?
They have higher boiling points than water which means they cook at higher temperatures and faster speeds
Why does cooking with oil give food a different flavour?
Because many of the flavours come form chemicals which are soluble in oil, meaning the oil carries the flavour
What does using oil increase when cooking?
The amount of energy we get from the food
Give examples of vegetable oils which can be processed and turned into fuels
Rapeseed oil and soybean oil
What do vegetable oils provide lots of which makes them good as fuels?
Energy
Which particularly useful fuel is made from vegetable oil?
Biodiesel
What kind of bonds do unsaturated oils have?
Double
What happens to bromine water when an unsaturated oil/fat is present?
It will decolourise
How can unsaturated oils be hardened?
By reacting them with Hydrogen
What is the name of the process when unsaturated oils are hardened?
Hydrogenation
What is the process of hydrogenation?
The unsaturated vegetable oils are reacted with hydrogen with the presence of a nickel catalyst at about 60 degrees celsius. The hydrogen reacts with the double-bonded carbons and opens out the double bonds
Why are vegetable oils hardened for use in foods?
Hydrogenated oils have higher melting points than unsaturated oils, so they are more solid at room temperature. This makes them useful for spreads, baking cakes and pastries
Is margarine hydrogenated?
No, it is partially hydrogenated to make it easier to spread
How many double bonds does a monounsaturated fat contain?
One
How many double bonds does a polyunsaturated fat contain?
More than one
Why are partially hydrogenated oils used over butter in processed foods?
The oils are a lot cheaper and they keep longer
What is a disadvantage of partially hydrogenated oils?
It results in a lot of trans fats which are meant to be very bad for you
Vegetable oils tend to be
Unsaturated
Animal fats tend to be
Saturated
Are unsaturated fats healthier or less healthy than saturated fats?
Healthier
Unsaturated fats reduce
Blood cholesteral
Partially hydrogenated vegetable oils increase
Blood cholesteral
Saturated fats increase
Blood cholesteral
Cooking with oil makes it more
Fattening
Oils do not
Dissolve in water
What is an emulsion?
Emulsions are made up of lots of droplets of one liquid suspended in another liquid. E.g. oil and water, you can have an oil-in-water emulsion or a water-in-oil emulsion
How do emulsions compare to oil and water?
They are thicker
Give an example of an emulsion
Mayonnaise is an emulsion of sunflower oil (or olive oil) and vinegar
How can emulsions be used in food?
They can be used as salad dressings and in sauces. E.g. a salad dressing made by the emulsion of olive oil an vinegar coats salad better than plain oil or vinegar. They can also be used in ice creams and whipped cream.
Advantages of emulsifiers
They provide better texture, coating ability and appearance
How else can emulsions be used?
In moisturising lotions, it’s easier to rub into the skin. other examples include cosmetics and paints
Oil and water naturally
Seperate
What is the structure of an emulsifier molecule?
On part is attracted to water and the other part is attracted to oil/fat
Which part of the emulsifier molecule is attracted to water?
The HydroPHILIC end of the molecule which latches onto water molecules
Which part of the emulsifier molecule is attracted to oil?
The HydroPHOBIC end of the molecule which latches onto oil molecules
What happens when you shake water an oil together?
The oil forms droplets surrounded by a coat of emulsifier
Which part of the emulsifier molecule is facing outwards?
The HydroPHILIC end
Why doesn’t the oil try to join with the other oil droplets and separate?
Because the oil droplets are repelled by the hydrophilic bit of the emulsifier facing outwards while the water molecules attach to the hydrophilic end. Meaning the two cannot separate out
Pros of emulsifiers
Gives products a longer shelf life. Allows companies to produce food lower in fat but still has a good texture
Cons of emulsifiers
Some people are allergic to certain emulsifiers
