High Hydrostatic Pressure

The application of high isostatic pressures enables food processors to produce high quality fresh food with an extended shelf-life, without the application of heat or the use of chemical preservatives.

 


Usually fresh products like vegetables, fruits and meat products have a relatively short shelf life under refrigerated storage. Hence, food processors have to add chemical preservatives or they have to apply heat (60°C-90°C for a few seconds up to a couple of minutes) to extend the shelf life of such foods. This heat process is called pasteurization and aims to inactivate all hazardous bacteria, but besides this positive effect it is often coupled to unwanted structural changes in the processed food. This includes softening, colour changes and often changes in the aroma, similar to the cooking of meat and vegetables at home.

An upcoming alternative to this classic preservation process is the high pressure pasteurisation of these kinds of foods. The tremendous advantage is that no heat has to be applied. That is also the reason, why high pressure processing is belonging to the group of the “non-thermal” technologies. In industrial scale, the processed food has to be packaged first, e.g. in a flexible pouch. Afterwards, it is loaded in the high pressure vessel, a big (55-687L) steel cylinder with a strong wall thickness. The vessel is connected to a high pressure pump or intensifier and completely filled with water until the wanted pressure is reached. The maximum pressure used for food processing is 6,000 bar, which is roughly 6-fold higher than the pressure at the deepest point of the ocean at 11,034 m depth. After a few minutes, the pressure is released and the pressurized food is unloaded. Contrary to a pressure application e.g. between two disks, the food does not change its shape and usually the colour and texture is preserved as well, which is due to the isotactic pressure transmission to objects in water. However, during the pressure application vegetative bacteria and other hazardous microbes are killed and hence, the food could be stored for a longer time but with a superior quality.

 

Figure: Photo of an industrial food high pressure processing unit ("Hiperbaric 420" by Hiperbaric)

 


This text was prepared by Kai Reineke, Berlin Institute of Technology (Technische Universität Berlin), Department of Food Biotechnology and Food Processing, Berlin, Germany.

For further questions please refer to: k.reineke@tu-berlin.de


 

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