Boiling point of vegetable oil is higher than water, so food is cooked at higher temperatures in oil. This means it cooks faster, and it changes the flavour, colour, texture of the food.
Some oil is absorbed and so the energy content of the food increases.
Unsaturated oils can be reacted with hydrogen so that some or all carbon double bonds become single bonds. This reaction is called hydrogenation and is done at about 600 degree Celsius using a nickel catalyst.
Hydrogenated oils have higher melting points because they are more saturated. Reaction called hardening because the hydrogenated oils are solids at room temperature.
· This means they can be used as spreads and to make pastries and cakes that require solid fats.
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