The same physical and mechanical effects which have been utilised in sonochemistry, i.e. strong shear forces, particle fragmentation, increased mass and heat transfer, nucleation of seeding, have been applied to food processing. Examples are quoted from various applications where power ultrasound has been used to influence the development of living cells, improve sterilisation and effect enzyme activity. Typically ultrasound can be used as a processing aid in extraction, crystallisation, freezing, emulsification, filtration and drying.