Ultra-high temperature processing or (less often) ultra-heat treatment (both abbreviated UHT) is the partial sterilisation of food by heating it for a short time, around 1-2 seconds, at a temperature exceeding 135°C (275°F), which is the temperature required to kill spores in milk. The high temperature also reduces the processing time, thereby reducing the spoiling of nutrients. The most common UHT product is milk, but the process is also used for fruit juices, cream, yogurt, wine, soups, and stews. UHT milk was invented in the 1960s, and became generally available for consumption in 1970s.
High heat during the UHT process can cause Maillard browning and change the sensory characteristics of dairy products.
UHT milk has a typical shelf life of six to nine months, until opened. It can be contrasted with HTST pasteurisation (high temperature/short time), in which the milk is heated to 72°C (161.6°F) for at least 15 seconds.