A pasteuriser is the industrial equipment that carries out pasteurisation, heating liquids to precise time-temperature combinations and cooling them rapidly afterward. The workhorse design is the plate heat exchanger: thin stainless steel plates with product flowing on one side and heating medium on the other, arranged so incoming cold milk is pre-warmed by outgoing hot milk in a regeneration section, saving enormous energy. Holding tubes ensure the required residence time at temperature, and flow diversion valves automatically return under-processed product for re-treatment, a critical food safety control. Tubular variants handle viscous products like cream or ice cream mix. Modern pasteurisers log temperatures continuously for regulatory compliance, and their hygienic design, with clean-in-place systems, prevents post-pasteurisation contamination, the main route by which pasteurised products become unsafe.