Chemistry - C1.6 - Plant Oils - Revision Cards in GCSE Chemistry

C1.6.1 - Extracting Vegetable Oils

Vegetable oils found in some seeds, nuts and fruit - can be extracted by crushing and pressing plant material then removing impurities
Have lots of energy and important nutrients when eaten
Release lots of energy when burnt in air - used as fuels - make biofuels eg. biodeisel
Molecules have hydrocarbon chains - with carbon double bonds -> unsaturated, many double carbon bonds in each molecule -> polyunsaturated
Unsaturated oils react with bromine water - orange -> colourless

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Vegetable oil boiling points are higher than water's -> can be cooked at a higher temperature -> cooks faster, changes colour and texture of food, food absorbs oil, increasing the energy content
Unsaturated oils + hydrogen -> some/all of carbon double bonds = single bonds - hydrogenation or hardening (solid at room temperature - used as spreads and make pastries and cakes - require solid fats)
Hydrogenation - done at 60C using nickel catalyst
Hydrogenated oils - more saturated -> higher melting points

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Oil and water - don't mix, usually separate, forming two layers - when mixed, tiny droplets form that can be slow to separate - emulsion
Emulsions - opaque and thicker than what they're made from - improves texture, appearance and ability to coat and stick - milk, cream, salad dressing and ice cream, some water based paints and many cosmetics are emulsions
Emulsifiers - stop oil and water from separating into layers - most emulsions contain emulsifiers to keep them stable
Emulsifiers - have a small hydrophilic part ('head') that is attracted to water and a long hydrophobic part ('tail') that is attracted to oil
The hydrophobic part goes into the oil droplet so the droplet is surrounded by the hydrophilic part - this keeps the droplets apart in the water -> stopping them from joining together and separating

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Advs of vegetable oils and emulsifiers in food:
- vegetable oils contain unsaturated fats - believed to be better for health than saturated fats
- vegetable oils are high in energy and contain important nutrients
- emulsifiers stop oil and water separating - makes food smoother, creamier and more palatable
Disadvs of vegetable oils and emulsifiers in food:
- animal fats and hydrogenated vegetable oils contain saturated fats - linked to heart disease
- emusified substances are high in fat and this may not be realised

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