Abstract: In a method of providing a brief heat treatment to a liquid by mixing steam therein followed by flash cooling at reduced pressure, very short and easily adjustable holding time at elevated temperature is obtained by adjustable increase of the amount of steam injected into the liquid to amounts exceeding those which condense by contacting the liquid. The method is efficient for heat treatment, such as sterilization, of heat sensitive materials including food products of high viscosity.

Abstract: In injection of steam, gas, liquid or a powdered or granulate product into a fluid in an injection apparatus having a substantially disc-shaped rotor (53), a product inlet (50) and a central product outlet (57), the injection is carried out in an annular injection zone above the disc-shaped rotor (53) at a distance from both the circumference and the center of the rotor (53). The fluid product which may be a liquid with considerable variation of dry solids content and viscosity is exposed to a radial displacement effect as well as a tangential dispersion effect.