Uperisation is a method of sterilising milk with pressurised steam — the name comes from the French ultra-pasteurisation. Milk is injected with culinary steam or passed through a steam chamber, bringing it almost instantly to around 150°C for a few seconds before rapid cooling, often with the steam then flashed off under vacuum. The extreme speed of heating and cooling gives excellent microbial kill with less cooked flavour than slower sterilisation methods. It is essentially a form of UHT processing distinguished by direct steam contact. Uperised milk keeps for months unopened at ambient temperature. The method suits large-scale production where throughput and energy efficiency matter, and the product behaves like other UHT milks.