During UHT treatment, direct steam injection or indirect heat exchangers raise the temperature of the food to around 135–145 °C for 2–5 seconds. These extreme conditions inactivate bacterial enzymes and denature proteins in cell membranes and spores. The short exposure time minimizes chemical changes in the food while ensuring lethality for thermoduric pathogens such as Bacillus and Clostridium. After heating, the product is rapidly cooled to prevent overcooking and is transferred into sterile containers under aseptic conditions. Because UHT processing achieves commercial sterility, it differs from pasteurization, which eliminates non‑spore‑forming pathogens but requires refrigeration to inhibit surviving spoilage organisms. UHT products can be stored unopened at ambient temperature for several months. UHT technology is widely used for milk, cream, plant‑based drinks, soups and sauces. In many European countries, UHT milk represents a large share of consumption because it can be transported and stored without a cold chain. The high heat load can cause slight caramelization of sugars and changes in protein structure, giving UHT milk a cooked flavor and altering its suitability for fermented products. Nutritional losses are minimal for most vitamins and proteins because of the short heating time. Advances in indirect heating and improved packaging materials have reduced off‑flavors and increased acceptance. UHT processing combines high temperatures with brief exposure and aseptic packaging to achieve long shelf life for liquid foods. It plays a key role in food safety and distribution, especially where refrigeration is limited. Related Terms: Pasteurization, Sterilization, Aseptic Packaging, HTST Processing, Shelf-stable MilkApplications and impact on food quality
