Hydrogenation is an oils and fats modification process.It is mainly used on vegetable oils like soya, rape, cotton or sunflower to increase their oxidative stability and to improve their melting properties by reducing their degree of unsaturation. As a result, these oils or fats reach a consistency that is ideal for use as margarine or shortening components.Hydrogenation is a reaction involving the use of a catalyst, most generally nickel, and is also an exothermic reaction.