Describe how and explain why vegetable oils are hardened for use in foods.

Vegetable oils are reacted with hydrogen at 60 degrees Celcius in the presence of a nickel catalyst. This process is called hydrogenation. Vegetable oils contain carbon to carbon double bonds meaning they are unsaturated. The process of hydrogenation converts these double bonds into single bonds causing the vegetable oils to become solid at room temperature. They can now be used as spreads.