Plate Heat Exchanger in Milk Pasteurization
Plate heat exchangers are widely used in milk pasteurization process, heating and cooling.
Ultra-high temperature processing (UHT), ultra-heat treatment, or ultra-pasteurization sterilizes food by heating it above 135 °C (275 °F) – the temperature required to kill spores in milk – for 1 to 2 seconds. UHT is most commonly used in milk production, but the process is also used for fruit juices, cream, soy milk, yogurt, wine, soups, honey, and stews.
The heat used during the UHT process can cause Maillard browning and change the taste and smell of dairy products. An alternative process is HTST pasteurization (high temperature/short time), in which the milk is heated to 72 °C (162 °F) for at least 15 seconds.
UHT milk packaged in a sterile container, if not opened, has a typical unrefrigerated shelf life of six to nine months. HTST pasteurized milk has a shelf life of about two weeks from processing, or about one week from being put on sale.
Ultra-high-temperature processing is performed in complex production plants, which perform several stages of food processing and packaging automatically and in succession:a.Heating
In the heating stage, the treated liquid is first pre-heated to a non-critical temperature (70–80°C for milk), and then quickly heated to the temperature required by the process.
Indirect heating systems
In indirect systems, the product is heated by a solid heat exchanger similar to those used for pasteurization. However, as higher temperatures are applied, it is necessary to employ higher pressures in order to prevent boiling. There are three types of exchangers in use:
- Plate exchangers
- Tubular exchangers
- Scraped-surface exchangers
For higher efficiency, pressurized water or steam is used as the medium for heating the exchangers themselves, accompanied with a regeneration unit which allows reuse of the medium and energy saving.
For more information about Plate Heat Exchanger via link: Plate Heat Exchanger