Extracting Plant Oils
- Plant oils can be placed over boiling water
- As the water evapourates, the water vapour will pass through the plants
- This evapourates the oil in the plants
- The oil and water vapours pass through a water jacket (which condenses the vapours)
- The liquid oil and water form an emulsion, which can easily be separeted to leave the oil.
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Extracting Plant Oils 2
- The plants can be crushed into a pulp (the pulp contains the oil and the crushed up plant materials)
- The plant materials can them be pressed inbetween metal plates to get the oil out
- The oil could be removed from the crushed plant material using a centrifuge
- Alternatively, solvents can be used to remove oil from plant materials.
- The oils that are collected can be distilled, which refines the oil, removing solvents, water, and impurities.
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Vegetable Oils in Food and Cooking
- Vegetable oils have a high energy content, and so they provide lots of energy.
- They also contain essential fatty acids, that help the body for metabolic processes.
- They have higher boiling points than water, which means that we can cook foods at higher temperatures at faster speeds than with water.
- Vegetable oils give food a different flavour. This is down to the oils own flavour, but also because the oils are able to carry the flavour of foods, which makes it seem more intense.
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Oils in Biofuels
- Rapeseed oil and soybean oil can be processed and turned into fuels.
- Vegetable oild have a high energy content, which makes them suitable for use as fuels.
- Biodiesel is a fuel thats made from vegetable oils.
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- Oils and fats are made up of long-chain molecules of carbon atoms.
- Unsaturated oils and fats have double bonds (=) between some of the carbon atoms in their chains.
- Because of this, unsaturated oils will decolourise bromine water (the bromine water opens up the double bond)
- Fats that are monounsaturated contain one c=c double bond, and polyunsaturated fats contain more than one.
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Unsaturated Oils 2
- Unsaturated oils are liquid at room temperature.
- We can harden them by reacting them with hydrogen. This needs to be done in the presence of a nickel catalyst at 60°
- This process is called hydrogenation. The hydrogen thats used opens up the double bond.
- The now hydrogenated oils have higher melting points than before, so they're more solid at room temperature.
- Hydrogenated oils are useful as spreads.
- Margarine contains partly hydrogenated oils. Changing all of the double bonds would make margarine too hard, so only some of the contents is hydrogenated.
- Partially hydrogenated oils are normally used in processed foods. This is because they're cheaper than butter, and they last longer, which gives the food a long shelf life.
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- Vegetable oils are usually unsaturated, while animal fats are normally saturated.
- Saturated fats are less healthy than unsaturated fats, because saturated fats increase the cholesterol in the blood, which increases our risk of heart disease.
- Natural unsaturated fats reduce the amount of blood cholesterol.
- Partially hydrogenated vegetable oils increase the amount of cholesterol in the blood, because they contain trans fats.
- Cooking food in any type of oil makes it more fattening.
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