A catalyst is a substance that affects, promotes or accelerates reaction of two or more substances to generate a different end product. Catalysts are often used in industrial processes, including food manufacture, to optimise manufacturing rates and volumes. Catalysis (the action of a catalyst) may also be used to change compounds to minimise their effect on processes, the environment and human wellbeing. Two key types of catalyst are in general use by industry today: catalyst support and true catalysts.

Catalysts themselves may be:

Homogenous – used in the solvent and intimately mixed with the reagents
Heterogenous – used in solid form as a contact ‘surface’ for the reagents