c1b oils, earth and atmosphere oils from plants. solar powered plants use energy from the sun:...
Post on 14-Dec-2015
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Solar powered
• Plants use energy from the sun: energy from sun
6CO2 + 6H20 C6H1206 + 6O2
• Plants turn glucose into other chemicals
• Can be useful to us
Vegetable oils• Rapeseed – vegetable oil• Collect seeds after plant
has flowered• Crushed, pressed to
extract oil• Impurities removed• Important food stuff
• Extraction using steam• Lavender oil - distillation• Plants boiled in water• Steam contains oil• Collected, water and
impurities removed
Oils as foods
• Contain loads of energy
• Hydrocarbon molecules
• May be saturated or unsaturated
• Tested with bromine water
Food/oil Energy in 100g (Kj)
Vegetable oil
3900
Sugar 1700
Animal protein (meat)
110
Cooking with veg oils: Boiling point
• Temperature depends on forces between molecules– Bigger force = higher boiling temperature
• Molecules in veg. oils are much larger than water molecules– Bigger forces– Higher boiling point
• Higher temperatures = different reactions• Food cooks differently
Soak it up
• Increases the energy content of the food
• Needs to be used
• Why can too much fried food be bad for you?• Food absorbs some of the oil it’s cooked in• Veg oils very high in energy
Hydrogenated oils
• Unsaturated oils are liquid at RToC– Double bond stops molecules fitting together
well– Reduces the forces between molecules
• Boiling point can be increased
• Adding hydrogen, replacing double bonds– Molecules fit together better– Increased forces = higher boiling point
Hydrogenated oils
• Higher melting point – solid at RToC
• “Hardening” of vegetable oils
• Hydrogenated oils
• Can be used to make spreads, margarine etc.
Smooth operator
• Texture of food is very important– Ice cream, mayonnaise etc.
• Mixture of oil and water – don’t mix!
• Can be persuaded– Very small droplets of oil– Spread throughout water– Emulsion
• Milk is an everyday example
Emulsifiers
• Encourages oil and water to stay mixed
• Egg yolk in mayonnaise
• Gives a thick texture
Preservation
• Need to make food last longer – preserve it– Salt (remove water)– Vinegar (pickling)– Alcohol (kill microbes)
• Knowledge of chemistry
• Also use chemistry to improve flavours or appearance
Food additives
• Substance added to a food– Food additive
• Approved for use in Europe– Given an ‘E’ number– Identify them rather than name them
• Eg.E102 is tartrazine (yellow colouring)
E220 is sulphur dioxide (preservative)• Six types of additive
Food additivesE number Additive What it does Example
E1xx Colours Improve the appearance of food. Can be natural, brownings or additives
E150 – caramel colour
E2xx Preservatives Helps food last longer = less wastage
E211 – sodium
benzoate
E3xx antioxidants Help stop food reacting with oxygen
E300 – vitamin C
E4xx Emulsifiers, stabilisers and
thickeners
Help improve the texture of food
E440 – pectin
E5xx Acidity regulator Helps control pH and taste E501 – potassium carbonate
E6xx Flavourings Blends flavours of food – sweet, sour, bitter, salt and
savory
E621 – monosodium
glutamate
Detecting additives
• Food scientists – investigate what has been added
• Complicated versions of simple techniques
• Chromatography– How well something dissolves in
a solvent– Solubility determines how far
they move across a surface– Separation technique
Fuels from plants
• Biodiesel - Name given to fuel made from vegetable oil
• Oil is treated to remove unwanted chemicals– Used on its own– Mixed with diesel refined from crude oil
• Other by-products:– Solid material = high energy cattle feed– Glycerine = used in soap
Benefits and advantages• Biodiesel gives off
carbon dioxide when burnt
• Biodiesel is grown• Crops used absorb
carbon dioxide as they grow
• C02 produced is absorbed by plants– Carbon neutral
• No greenhouse gases
• Very clean in terms of pollution– Very little sulphur
dioxide
• Not harmful to animal and plant life
• If spilled, breaks down much faster than ‘normal’ diesel
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