Chapter 6 - Plant Oils Flashcards
Why are vegetable oils important
- When eaten, they provide us with a lot of energy and important nutrients.
- They release a lot of energy when they burn in the air and so can be used as fuels.
What does polyunsaturated mean
Several double bonds in each molecule
Why are vegetable oils useful in cooking
The boiling points of vegetable oils are higher than water so good is cooked faster. It also changes the flavour, colour and texture of food. Energy content of food increases as some of the oil is absorbed
What is hydrogenation
Reaction unsaturated oils with hydrogen so that some or all of the double bonds become single bonds. This is done at about 60 degrees Celsius using a nickel catalyst. The hydrogenated oils have higher melting points because they are more saturated. This reaction is also calls hardening because the hydrogenated oils are solids at room temperature. Can be used as spreads.
What is an emulsion
A mixture that contains tiny droplets that can be slow to separate.
What are the qualities of emulsions
They are opaque and thicker than oil and water. This improves their texture, appearance and ability to coat and stick to solids.
What are emulsifiers
Substances that help stop the oil and water from separatist into layers.
How do emulsifier molecules work
Emulsifier molecules have a small hydrophilic head attracted to water. They also have a long hydrophobic part is attracted to oil. The hydrophobic parts of many emulsifier molecules go into each oil droplet and so the droplets become surrounded by the hydrophilic parts. This keeps the droplets apart in the water, preventing them from joining together and separating out.
What are the benefits of vegetable oils
They contain unsaturated fats which are believed to be better for your health than saturated fats
What are the advantages and disadvantages of emulsifiers
Advantage:
-Makes food smoother, creamier and more palatable
Disadvantage:
-You may be tempted to eat more because they taste better and it is less obvious that they are high in fat
How can vegetable oil be extracted
By crushing and pressing the plant material, followed by removing water and other impurities
OR
By distilling the plant material mixed with water. This produces a mixture of oil and water from which oil can be separated
