C1b Oils, Earth and Atmosphere

Oils from Plants

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

Emulsion paint

• Emulsion paint is NOT an emulsion!

• It is a powder suspended in a liquid– Colloid

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

Other bio-fuels

• Ethanol (alcohol)– Fermenting sugar from sugar cane– Used in Brazil a lot – added to normal petrol

• Gives off CO2 when burnt

– Absorbed by plants during photosynthesis

• Ethanol can also be made from etheneC2H4 + H20 C2H5OH

• Not carbon neutral