A method and device related to a liquid product pressure and (optionally) temperature treatment method reduces the level of microorganisms in the liquid product to a preselected level. Utilizing the method, liquid product is diffused in a chamber with the speed of pressure variation of liquid product in one embodiment of about 10.sup.9 Pa/sec. The preferred speed of the diffused drops is about 10 m/sec. The liquid product can optionally be heated before or during diffusion, and is preferably heated as a diffused liquid product by mixing it with superheated steam. The device includes a chamber and a diffuser in communication with the chamber. Optionally, the device may include a heating apparatus, such as a steam generator connected via a pressure control valve to a steam super heater, a cooling chamber connected via a pressure control valve with a condenser, a vacuum pump in communication with the chamber, units for condensation and collecting finished products and a vacuum control unit in communication with the chamber.