A hydrogenation catalyst is a substance that speeds up the chemical reaction of hydrogenation, where hydrogen is added to unsaturated organic compounds. This process is commonly used in the food industry to convert liquid fats into solid fats, improving texture and shelf life. Common catalysts include metals like nickel, palladium, and platinum. These catalysts work by providing a surface for the reactants to interact, lowering the energy needed for the reaction to occur. The choice of catalyst can affect the reaction rate and selectivity, making it crucial for producing desired products in various industrial applications, including the production of biodiesel and pharmaceuticals.