Plant oils and their uses Flashcards
What are some fruits, seeds and nuts rich in?
Give the two stages in making plant oils.
Give the two stages in an alternative method of making plant oils.
Some fruits, seeds and nuts are rich in vegetable oils.
The oils can be extracted from fruits, seeds and nuts by crushing and pressing the plant material.
2) Water and other impurities are then removed.
1) Some oils are extracted by distilling the plant material mixed with water, this produces a mixture of oil and water. 2) The oil can is then separated from this mixture.
Give four reasons why vegetable oils are useful in terms of food and cooking.
1) They provide a lot of energy, and also contain nutrients.
2) They have higher boiling points than water, so they cook foods at higher temperatures than the process of boiling.
3) They cook foods quicker and usually give the food better flavour and texture
4) Some of the oil is absorbed so the energy content of the food increases.
What is an emulsion?
What is different about an emulsion, than the separate liquids? Give four differences.
What are examples of common emulsions?
An emulsion is a mixture of liquids, in this case oil and water that do not dissolve in each other.
1) Emulsions are opaque and thicker than the oil and water they are made from.
2) They have a better texture.
3) They have a better appearance.
4) They are sticky and so suitable for coating solids (cosmetics, paint).
Salad dressing, milk, ice cream, cosmetics and paint.
Describe the structure of an emulsifier molecule.
How does an emulsifier prevent the oil and water from separating?
They have a small hydrophilic ‘head’ that is attracted to water and a hydrophilic ‘tail’ that is attracted to oil.
The hydrophobic tail of many emulsifier molecules goes into each oil droplet and so the droplets become surrounded by the hydrophilic head. This keeps the droplets apart in water, preventing them from joining together and separating out.
What does the bromine water test show?
It turns from orange to colourless when mixed unsaturated oil.
How are unsaturated vegetable oils hardened?
Why are vegetable oils hardened and what does this make them useful for?
Reacting them with hydrogen so that some or all of the carbon double bonds become single bonds. This reaction is called hydrogenation and is done at about 60ºC using a nickel catalyst.
The hydrogenated oils have higher boiling points because they are more saturated, hydrogenated oils are solid at room temperature.
This means they cane be used as spreads and to make pastries and cakes that require solid fats.
What do unsaturated oils contain?
Carbon double bonds
What is an emulsifier?
Emulsifiers are substances that help to stop the oil and water in an emulsion from separating into layers, most emulsions contain emulsifiers to keep the emulsion stable.
Give three benefits and two drawbacks of using vegetable oils or emulsifiers in foods?
Benefits
1) Vegetable oils are high in energy and contain important nutrients.
2) They contain unsaturated fats which are better for your health than saturated fats.
3) Emulsifiers stop oil and water separating which makes food smoother, creamier and more palatable.
Drawbacks
1) Animal fats and hydrogenated vegetable oils contain saturated fats, which have been linked to heart disease.
2) As a result of emulsifiers making foods taste better and it is less obvious that they are high in fat, you may be tempted to eat more.
