Unit 1: 6 - Plant oils Flashcards
How are vegetable oils extracted from oil-rich plants like nuts, seeds and fruits?
First, the plant material will be crushed and pressed, then water and other impurities are removed. Some oils are extracted by distilling the plant material mixed with water. This then produces a mixture of oil and water from which the oil can be separated.
How can vegetable oils be used as a renewable energy source?
They can be made into biodiesel, which can be burnt in car engines.
How can we test for unsaturated oils?
By reacting them with bromine water (they will turn it colourless).
What type of molecules are vegetable oils?
Hydrocarbons.
What do we call an oil with several double C=C bonds?
Polyunsaturated.
What do we call an oil with no C=C bonds?
Saturated.
Why are vegetable oils useful in cooking?
The boiling points are higher than water so food is cooked at higher temperatures in oil, meaning it cooks faster. It also changes the taste and texture of the food, and gives it more energy.
What do we call the reaction that involves making unsaturated fats saturated? What does it entail?
Hydrogenation or ‘hardening’. This involves reacting the unsaturated fat with hydrogen at around 60 degrees with a nickel catalyst.
What is a mixture between oil and water that wouldn’t usually mix?
An emulsion.
Give an example of an emulsion.
Milk.
Give 2 properties of emulsions.
They are opaque and they are thicker than the oil and water they are made from.
What is an emulsifier?
A substance that helps stops the oil and water from separating into layers.
Describe an emulsifier molecule.
The hydrophobic tail is attracted to the oil. The hydrophilic head is attracted to the water. Each oil droplets contain many hydrophobic parts of emulsifier molecules, so the droplets become surrounded by hydrophilic heads which stops oils joining together and separating from the water.
What type of fats are generally considered to be better for your health?
Unsaturated fats, as they contain important nutrients and not as high energy content as saturated fats. Saturated fats have also been linked to heat disease.
Why are emulsified fats used in food?
Because they taste better and have a better texture.
