Posted on 29th Nov 2011 @ 1:55 AM

Aseptic processing of a product by pre-sterilizing the package and then aseptically filling and sealing the package with a sterile product has two different advantages compared to either "fill, seal, heat & chill" (most canned products) or "hot fill & cool" (most acid/acidified liquids in bottles) methods:

•  Better quality due to less heat damage

• Reduced energy consumption

For products sterilized in cans or bottles, motion of the containers is the only way to achieve sufficient convection currents to accelerate temperature equilibration. To achieve sterilization, a certain time and temperature exposure is needed to eliminate microbes. The time to reach a uniform killing temperature in the product causes over sterilization in most of the product and a certain level of heat damage to the product. This heat damage is repeated during the slow, convection cooling after achieving the kill temperature.

If the product is pre-heated using a thin layer in a heat exchanger (e.g. plate heat exchanger) then filled at the target killing temperate (hot fill process), the heat damage is minimized for achieving the kill temperature, but now the product needs to be chilled to minimize post process heat damage.  Since the product now relies on convection cooling, there is heat damage and over sterilization during the cooling step.

However, with aseptic processing, the process takes advantage of both quick heat up and quick cool down to minimize heat damage. The product is quickly heated using a thin film heat exchanger to the target kill temperature, held for the time necessary for sterilization, then quickly chilled, again using a thin film heat exchanger.  The exposure of the product to heat damage is minimized during heating and chilling.

Aseptic processing advantages are accentuated by the fact that higher temperatures and much shorter times can be used in sterilizing so that the process can be executed in seconds rather than minutes. The energy costs are minimized and quality is maximized.

Dr. Richard Meyer
R S Meyer & Associates LLC
Federal Way, Washington