Pasteurization Process Technology - The process of pasteurization was named after Louis Pasteur, a French chemist / microbiologist, who discovered that spoilage organisms could be inactivated in wine by applying heat at temperatures below its boiling point. Actually he only needed to heat the wine to 131 °F (55 °C) for a few minutes to kill the microorganisms that caused the wine diseases. The process was later applied to beer and milk (and many other products) and remains one of the most important unit operations in food, dairy and beverage processing facilities.
Continuous pasteurization has numerous advantages over the batch (a.k.a. vat) pasteurization. The most important being time, hygiene and cost of operation (i.e. energy saving). For most continuous pasteurization processes, a high temperature short time (HTST) pasteurizer is employed. The heat treatment can be achieved by using either a plate heat exchanger (PHE) or a tubular heat exchanger. The plate heat exchanger consists of a stack of corrugated stainless steel plates clamped together in a frame. There are several flow patterns that can be used depending on the application (wide gap cross-section for liquids with pulp and fiber, double-wall plate heat exchangers preventing cross-contamination, energy efficient plates with the best heat-transfer patterns, etc). Gaskets are used to define the boundaries of the channels and to prevent leakage. The heating medium is normally steam or hot water. Tubular heat exchangers are used when the fluid contains particles and pulp that can block the channels of a normal plate heat exchanger (PHE).
Ultra Pasteurization (UP) is a process similar to HTST pasteurization, but using slightly different equipment, higher temperatures and longer times. UP pasteurization results in a product with longer shelf life but still requiring refrigeration. Another method, Ultra High Temperature (UHT) sterilization raises the temperature of milk to at least 280° F for two seconds, followed by rapid cooling. UHT-pasteurized milk that is packaged aseptically results in a "shelf stable" product that does not require refrigeration until opened.
|Dairy Pasteurization Table - note that the temperatures and the pasteurization times are not applicable for egg products.|
|63°C (145°F)||30 minutes||Vat Pasteurization|
|72°C (161°F)||15 seconds||High temperature short time Pasteurization (HTST)|
|89°C (191°F)||1.0 second||Ultra Pasteurization (UP)|
|90°C (194°F)||0.5 seconds||Ultra Pasteurization (UP)|
|94°C (201°F)||0.1 seconds||Ultra Pasteurization (UP)|
|96°C (204°F)||0.05 seconds||Ultra Pasteurization (UP)|
|100°C (212°F)||0.01 seconds||Ultra Pasteurization (UP)|
|138°C (280°F)||2.0 seconds||Ultra-high temperature (UHT) Sterilization|
|Source: IDFA website. Page headlined: Pasteurization: Definition and Methods - http://www.idfa.org/files/249_Pasteurization%20Definition%20and%20Methods.pdf (PDF).|
A pasteurization system normally contains the following components:
Flash pasteurization works by rapidly heating a beverage to a temperature of around 160 -180°F prior to the filling and capping process. The beverage will be kept at this temperature for less than 20 seconds prior to being rapidly cooled via another heat exchanger. This process has some space and cost advantages due to handling the beverage in bulk before filling. The disadvantage of flash pasteurization when compared to tunnel pasteurization is that it requires sterile filling and sterile containers. Keeping the containers and filling system sterile is complex, difficult and expensive. By comparison, tunnel pasteurization processes keep the beverage in a sealed container avoiding contamination issues and guarantee shelf life. Consequently, the majority of beer bottles and cans are pasteurized in tunnel pasteurizers.
Note: GEA Process Engineering Inc. (GEA Liquid Processing) represents Tuchenhagen Dairy Systems, Tuchenhagen Beverage Systems, GEA Diessel, Scami and GEA Ahlborn in North America. GEA Liquid Processing typically utilizes: GEA Ecoflex plate heat exchangers, Westfalia Separator clarifiers, and Niro Soavi high-pressure pumps and homogenizers. GEA has over the years supplied hundreds of pasteurization systems all over the world in compliance with local codes, standards, restrictions and customs. In the US dairy industry we obviously adhere to the USDA and 3A guidelines.
For additional information about our ESL (extended shelf life) approach and technologies please access this page: Extended Shelf Life Processing.