Efficient high pressure treatment of foods

A CLEAR trend towards more naturalness, combined with ever increasing requirements by the supervisory authorities for the exclusion of harmful microorganisms from foods, has meant that the high-pressure treatment of packaged foods is gaining in importance. With high-pressure treatment packaged food is subjected for a sufficiently long period to a high pressure of up to 6,000 bar in a so-called autoclave, which is a lockable and gas tight pressure container. Through this reliable process, microorganisms in the food such as Listeria and Salmonella are killed. As the process is conducted under ambient temperature, even heat-sensitive food products can be treated and are preserved for up to four times longer. At the same time, the original nutritional value and taste remain nearly unimpaired.

Multivac has developed a concept for integrating equipment for the high-pressure treatment of foods into fully automatic packaging lines. This means that for the first time the high-pressure treatment of foods within the packaging process can be seen as a viable option. As one of the first packaging manufacturers worldwide to master the process, Multivac can offer it not only for vacuum- but also for MAP packs. The necessary technical innovations have already been filed for patent.

Integrated solutions

Until now, high-pressure treatment was mostly carried out in a separate manufacturing stage and, moreover, the manual loading of the high-pressure container is not very efficient. With some new technical innovations (patent pending), Multivac has developed a pioneering solution for the line integration of high-pressure equipment for the treatment of packaged foods. The solution comprises a high-pressure unit and an automisation system to address packaging efficiency.

ThyssenKrupp daughter company, Uhde High Pressure Technologies, developed the HPP unit consisting of one or more autoclaves. The automation concept integrates the process into packaging lines, which are laid out to meet the demands of the food industry.

Highest possible machine throughput

With this HPP integration solution, the finished food packs are automatically loaded into the transport containers (patent pending) and, following the high pressure treatment in the autoclave, automatically unloaded, dried, printed or labelled if required, and finally packed into cartons. "In this way, it is for the first time that we can process large, industrial scale production quantities fully automatically in a quasi continuous operation," explains Tobias Richter, product manager in the Systems Business Group, and responsible for high pressure equipment at Multivac.In order to achieve as high a machine throughput as possible, the available space in the autoclave must be used as intelligently as possible. "Since the high pressure equipment is round for reasons of optimising the distribution of pressure forces, the loading pattern also has to be designed accordingly," Mr Richter points out.

He adds that with a favourable pack shape it is possible to handle two to four tonnes of packed food per hour in the high-pressure equipment.

MAP pack concepts

As the only manufacturer to date worldwide, Multivac has also mastered the high-pressure process for MAP packs. The packaging specialist from the Allg?u designs not only high pressure stable MAP pack concepts but has also in co-operation with Uhde High Pressure Technologies optimised the HPP unit itself so that the high pressures in the autoclave are relieved in a controlled manner.

"With the help of so-called 'holding torque' we create short rest periods in which the polymer can regenerate. In this way the packaging material is stressed coadidas