In 1950s, European dairy researchers began to develop UHT sterilization technology, aiming at the phenomenon that the original method of canned food processing (120℃, 15 minutes, see table 1) was used to make "fresh-keeping and sterilization" milk, which seriously damaged the nutritional function of milk. Due to the direct contact between high-temperature and high-pressure water vapor and low-temperature milk, some water vapor will inevitably condense into the milk while the milk is rapidly heated and sterilized, resulting in additional water entering the product, which is not allowed by dairy regulations. However, in this case, the milk is actually at a high temperature of about 140℃ and the pressure is about three atmospheres. Once the pressure is released, the temperature will drop immediately, and some water will escape in the form of steam, which is the application of the so-called "flash evaporation" technology in dairy industry.