Plant oils and their uses Flashcards
Some fruits, nuts and seeds are used for extraction of oil. Why?
They are naturally rich in oils.
Oil can be extracted from plants, seeds etc. by two methods. What are these methods?
1) Crushing/pressing
2) Distillation
Vegetable oils are important. How?
They store large amounts of energy, can be used as fuels and provide us with many nutrients.
Vegetable oils are useful in cooking because…
…they have higher boiling points than water meaning that food can be cooke to a higher temperature than boiling. Furthermore, this reduces the time it takes to cook, but it increases the energy content when the food is eaten.
What is an emulsion?
A substance that is a mixture of oil and water meaning that it is thicker than oil/water.
Examples of emulsions.
Mayonaise, milk, paint.
What is an emulsifier?
Water and oil don’t naturally stay mixed, they will separate when left to stand. An emulsifier binds the water and oil so they do not separate as quickly.
How does an emulsifier work.
It has a hydrophilic and a hydrophobic end. The hydrophilic head binds to the water and the hydrophobic tail binds to the oil keeping oil droplets suspended in water or vice versa.
What is meant by hardening unsaturated vegetable oils?
Heating at 60C in the presence of a nickel catalyst. This is known as hydrogenation as hydrogen adds to the carbon bonds making them saturated.
Why are vegetable oils hardened (hydrogenated)?
It makes them solid at room temperature (increased melting point) so they can be used as spreads or in cakes and pastries.
