Unsaturated oils can be made harder
Unsaturated vegetable oils are liquid at room temperature.
They can be hardened by a process called Hydrogenation.
In the presence of a nickel catalyst, hydrogen is reacted with the oil at 60'C.
The reaction opens the double bonds between the carbon.
Unsaturated: - Low melting point
- Liquid (room temp)
- Double bonds
Saturated: - Higher melting point
- Solid-ish (room temp)
- Single bonds
In margarine, if all the unsaturated fats are hydrogenated, it would be too hard. Therefore, hydrogenating most of them make it spreadable.