What is UHT and HTST Pasteurization

What is UHT and HTST Pasteurization?

Ultra-High Temperature (UHT) processing and High-Temperature, Short-Time (HTST) pasteurization are two pasteurization methods that involve heating liquid foods to a specific sterilization temperature for a precise, short time, followed by rapid cooling before packaging. The precision heat treatment is designed to sufficiently sterilize fresh beverages, dressings or sauces to commercial requirements while maintaining flavor, color, and nutrients. UHT and HTST are heated for a much shorter amount of time than the original vat pasteurization technique. This is possible due to the higher temperatures involved.

While UHT and HTST are both high temperature pasteurization techniques, there are some differences. UHT pasteurization – sometimes called UHT sterilization or aseptic processing – is carried out at higher temperatures than HTST pasteurization. It is typically used for milk, cream, and other dairy products but can also be used for juices and other beverages. In UHT processing, the beverages are heated to a higher temperature for a shorter amount of time and then packaged directly into a hermetically sealed container in an aseptic process. UHT processed beverages are shelf-stable for two to three months without refrigeration.

HTST, sometimes called flash pasteurization, is an efficient continuous processing method for large batches. It is also used for sterilizing dairy products including yogurt and can be used for more viscous foods such as soups and sauces. The products are fed continuously through a sanitary plate heat exchanger heated by steam or hot water, and then cooled rapidly through a cooling section before bottling. The temperature and time profile varies depending on the product but is a lower temperature and longer time than the UHT process in general. Dairy products and fresh beverages processed using HTST must be refrigerated.

Both UHT and HTST are exacting processes requiring extremely accurate temperature and pressure control for the final product to meet government regulations and customers’ taste expectations. Constant pressure modulating valves are often used for pressure control in UHT and HTST processing.

How do Constant Pressure Modulating Valves Work?

Constant pressure modulating valves (CPM), sometimes called constant pressure valves, adjust to system changes in pressure and flow to maintain uniform pressure in the process lines. Often used in HTST and UHT processing of juices, milk, vinegar, yogurt and other foods and beverages, CPM valves can be 3A sanitary rated. These regulating valves provide accurate pressure control for safe and reliable product outcomes and have excellent cleanability, as required in the food and beverage industry.

In case of process-related pressure fluctuations due to temperature changes or product viscosity shifts, CPM valves open or close instantly to compensate. The set-point for the valve is set by an air supply on top of the valve, so a constant air supply is required to control pressure using a CPM valve.

Air Loaded Sanitary CPM Valves by Steriflow Food & Beverage

Constant pressure modulating valves by Steriflow Food & Beverage, the FMCPM Series, are designed to maintain the precision pressure required in UHT and HTST processing.

Learn how they work: