Tunnel Machines

Pasteurization is a process that uses heat to kill the bacteria that cause spoilage in food and beverage products. Pasteurization tunnels pasteurize the finished can or bottle in a continuous flow process. Pasteurization is different from sterilization in that it does not kill all bacteria in the product.

The pasteurizer tunnel is wide to allow for long dwell times in the chamber without being unnecessarily long. Some tunnels are double layer to conserve floorspace while allowing sufficient dwell time. Bottles or cans come from capping or seaming to the tunnel infeed. As the containers usually come in single, or narrow file some means of spacing them out across the width of the pasteurizer is employed.

Flow through the tunnel may be accomplished by a conveyor belt or chain, by roller conveyor or by walking beam. A walking beam conveyor consists of a series of interleaved stationary and moving bars. As the product rests on the stationary bars, the moving bars raise it up, move it forward slightly, then retract leaving the product sitting on the stationary bars. This cycle repeats continuously.

Passing through the tunnel, the product is sprayed with gradually wamer water until it reaches an internal temperature varying from 160-180 degrees F depending on product.

The product is held at the pasteurization temperature for a defined period of time depending on product and temperature. A higher temperature permits shorter dwell time, lower temperatures require a longer dwell for adequate microbial kill.

Pasteurization time is controlled by the conveyor speed and length through the pasteurizer.

Once pasteurized, the product is cooled back to room temperature. As it exits the tunnel, it is generally speeded up and eventually single filed for labeling, bundlng and wrapping or another packaging process.