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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Unsaturated Oils
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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Health
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 oilsincrease 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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