What is UHT milk?
UHT milk is often called long-life milk or box milk. UHT, short for ultra-high temperature treatment, is a process used to produce milk with a long shelf life. It involves heating milk to a very high temperature (135 °C to 150 °C) for a few seconds and then cooling it to 4 °C or lower. Unopened UHT milk can be stored unrefrigerated for a long time, as indicated on the package. But, once opened, it must be treated like fresh milk and be kept refrigerated and used within three to four days.