Extracting Oils from Plants
pressing - the material is crushed and the oil is squeezed out, then in centrifuge (spinning in a container). the oil is at the top and the material at the bottom.
Steam Distillation - the material is warmed up gently, suspended over boiling water. the steam and oil condeses into a beaker.
in both of these processes - water and other impurities are removed leaving relatively pure oils
vegetable oils and diet
fats from animal sources eg lard, butter ect are solid oils and have similar chemical composition
both fats and oils are an important part of your diet if you body is to work properly. 1g of oil contains 34kJ of energy. 1g of carbohydrate contains 9.6kJ of energy.
important vitamins are supplied by oils such as a, d, e and k
using oil makes things taste nicer, but gives the food more calories. for example potatoes that are cooked in boiling vegetable oil have more calories but potatoes that are cooked in boiling water taste boring.
saturated and unsaturated fats
both vegetable oils and animal fats are quite complicated compounds containing things called fatty acids, these are compounds of the elements carbon, hydrogen and oxygen.
these fatty acids contain long chains of carbon atoms, aprox 16 atoms long.
some of these carbon chains contain double bonds and are called monounsaturates.
some contain no double bonds and are saturated.
some contain several double bonds and are polyunsated.
a carbon carbon double bond looks like c=c and a single bond looks like c-c
animal fats and vegetable oils
animal fats vegetable oil
examples butter, suet, lard sunflower oil, olive oil
chemical makeup saturated mono/polyunsaturated
melting points high - solid at room low - liquid at room t empreature tempreature
effects on health heart disease, high lowers blood preassure cholesterol, obesity, high blood preassure lower cholesterol less risk of heart heart disease
testing for unsaturated fats
bromine water can be used to test for double bonds, when added to an unsaturated fat it turns from a yellowy brown colour to colourless.
an alternative is iodine water
when added to these substances the changes are:
- olive oil - decolourised
- lard - stay orange/brown
- palm oil - decolourised
- butter - stay orange/brown
- margerine - decolourised.
to test which substance has the most double bonds, bromine water is repetely added, the longer it takes of for the bromine water to stay orange/brown the more double bonds
Making margerine from vegetable oils
the fatty acids in vegetable oil are usually polyunsaturated.
these fatty acids can be reacted with hydrogen in the presence of a nickel catalyst at a tempreature of 60degreesC ish - some of the double bonds will be broken.
getting rid of SOME of the bonds makes the oil harder and increases the melting point and turns it into a soft spread like margerine.
these margerines still contain one or more double bond so are often softer that animal fats and are thought to be healthier
Amount of bromine water decolourised
Effects on health
State at room temp.