pasteurization is usually done to milk, which was first suggested by franz von soxhlet in 1886. there are two popular ways to pasteurize milk. first, high temperature/short time (htst), and second, ultra-high temperature (uht). htst is the most common method. milk only labeled "pasteurized" (or "past") is usually treated with the htst method, whereas milk labelled "ultra-pasteurized" or "uht" must be treated with the uht method. htst is when the milk is at a temperature of 72 degrees celsius (or 161.5 degrees fahrenheit) for at least 15 seconds. uht is when the milk is at a temperature of 138 °c or 280 °f for at least two seconds.