Pasteurisation
Continuous pasteurisation has several advantages over the batch (vat)
pasteurisation method, the most important being time and energy saving. For
most continuous processing, a high temperature short time (HTST) pasteuriser is
used. The heat treatment is achieved 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. Gaskets are used to define the
boundaries of the channels and to prevent leakage. The heating medium are
normally steam or hot water. Tubular heat exchangers are employed when the
fluid contains particles that would block the channels of a plate heat
exchanger.
Ultra Pasteurisation (UP) is a process similar to HTST
pasteurisation, but using slightly different equipment, higher temperatures and
longer times. UP pasteurisation results in a product with longer shelf life but
still requiring refrigeration. Another method, Ultra High Temperature (UHT)
sterilisation raises the temperature of milk to at least 280° F for two
seconds, followed by rapid cooling. UHT-pasteurised milk that is packaged
aseptically results in a "shelf stable" product that does not require
refrigeration until opened.
A pasteurization system normally contains the following
components:
• Balance tank with a float valve assembly
•
Regenerator
• High-pressure homogenizer
• A centrifigal pump with
magnetic flow meter and controller
• Holding tube
• Recorder-controller
• Flow diversion device
• Separator (clarifier)
• + some process
automation and process integration.