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What you need to know
Reflections and Exam tips
Plant oils and their uses
Many plants produce useful oils that can be converted into consumer products including processed foods. Some fruits, seeds and nuts are rich in oils that can be extracted.
There are two ways to extract the oils:
Water and other impurities are removed.
Vegetable oils are unsaturated (due to their C=C double bonds) and are referred to as polyunsaturated fats. Unsaturated fats can be detected by adding bromine water. Bromine water turns from orange-brown to colourless when it reacts with unsaturated fats.
Cooking with Vegetable oils
Vegetable oils are important foods and fuels because they provide a lot of energy. They also provide nutrients such essential vitamins e.g. olive oil contains vitamin E.
Vegetable oils have higher boiling points than water and so can be used to cook foods at higher temperatures than by boiling.
This produces quicker cooking and different flavours, but it increases the energy that the food produces when it is eaten. Unsaturated fats (olive oil) are healthier than saturated fats (butter), as saturated fats block up arteries causing heart disease.
Unsaturated liquid oils turned to solids (margarine) by partially saturating the oil (removing the double bonds to make single bonds). Hydrogenation increases the melting point of the vegetable oil. Hardening makes the vegetable oil solid at room temperature so they are spreadable. The oil is heated at very high temperature (60°C) in the presence of nickel catalyst.
Describe where vegetable oils come from.
Give uses for vegetable oils.
Explain what happens when oil mixes with water.
Compare saturated and un-saturated vegetable oils.