How does UHT processing affect shelf life compared with HTST?

• A. UHT yields shelf-stable milk that can be stored at room temperature in unopened packages; HTST requires continuous refrigeration
• B. HTST shelf-stable at room temperature; UHT requires refrigeration
• C. Both are shelf-stable at room temperature
• D. Neither is shelf-stable

Answer: (A)

The main idea is that UHT processing aims for commercial sterility, while HTST pasteurization is designed to reduce pathogens but not achieve sterility. UHT milk is heated to very high temperatures for a short time and then packaged in sterile, airtight containers. This combination makes the milk effectively free of viable microbes in the unopened state, so it can be stored at room temperature. HTST milk is heated enough to greatly reduce harmful organisms, but it isn’t kept in a sterile condition and isn’t packaged to stay sterile; unopened HTST milk generally must be kept refrigerated to prevent spoilage. After opening, both types should be kept refrigerated and consumed relatively soon, but the unopened shelf life at room temperature is what sets UHT apart.