Pasteurization is a process named after scientist Louis Pasteur which uses the application of heat to destroy human pathogens in foods. For the milk processing industry, the terms "pasteurization," "pasteurized" and similar terms mean the process of heating every particle of milk in properly designed and operated equipment to one (1) of the temperatures given in the following chart and held continuously at or above that temperature for at least the corresponding specified time:

The most common method of pasteurization in the United States today is High Temperature Short Time (HTST) pasteurization, which uses metal plates and hot water to raise milk temperatures to at least 161°F for at least 15 seconds and is then cooled rapidly. Higher Heat Shorter Time (HHST) is a process similar to HTST pasteurization, but it uses slightly different equipment and higher temperatures for a shorter time. For a product to be considered Ultra Pasteurized (UP), it must be heated to at least 280°F for two seconds. UP pasteurization results in a product with longer shelf life but still requiring refrigeration.

Another method, aseptic processing, which is also known as Ultra High Temperature (UHT), involves heating the milk using commercially sterile equipment and filling it under aseptic conditions into hermetically sealed packaging. The product is termed "shelf stable" and does not need refrigeration until opened. All aseptic operations are required to file their processes with the Food and Drug Administration's (FDA) "Process Authority." There is no set time or temperature for aseptic processing; the Process Authority establishes and validates the proper time and temperature based on the equipment used and the products being processed.