Limitation : Product That Is Not Suitable Using HPP

Although HPP can pose lot of benefits, however it can't be used on certain types of food product such as ; 

Spices, powder and extracts

Dry products such that are not suitable for HPP because of isostatic pressure needs water inside the food product for its homogeneous, uniform, efficient transmission and consequently to cause an inactivation of the microorganisms present in the product. Powders and spices have;

• too low water/humidity content
• too low Aw values

HPP will create a more compact matrix, but the pressure will not be transmitted throughout the product and will not tackle the microbes.

Dried nut, fruit or cereals

Similar to the above mentioned case. Such products have low water content and low values of water activity. HPP is not effective in extending the shelf life or generally improving the safety of such products.

Whole fruits

HPP makes all the sense if you clean a fruit; slice it, chop it or dice it; mix it perhaps with other ingredients; pack it in adequate flexible, sealed formats… and then high pressure process it for shelf life and safety while maintaining its attribute.

But it does not really make sense for whole, raw fresh fruit. Fresh pieces of produce do not constitute such a high value product, and more importantly, the isostatic pressure causes certain changes in the texture and in the cell walls. Raw, fresh fruit submitted to high pressure will certainly have a great quality from the microbial point of view; but with the noticeable changes in the fruit matrix and the evacuation of all the air that was trapped in the fruit flesh, it is not a marketable proposition, in general.

Vegetable leaves and leafy salads

Similarly, HPP does not pose a good solution for leafy vegetables. Isostatic pressure provokes certain changes in the structure of the vegetable cell walls. After HPP, leaves of i.e. spinach, rocket, lettuce etc. appear more mushy, more flaccid and more exudative. High Pressure Processing is, on the other hand, a fantastic value proposition for wet salads and vegetable based sandwich fillings

Bread & pastries

The comments below apply to any product with a lot of trapped air, fluffy or with a mousse-like structure:

Basically if you put a fan of bread, or a croissant, through an HPP system, you will obtain a flat, collapsed piece of pastry. Why? Breads and pastries have a huge amount of “empty spaces” in their matrix, a lot of trapped air. Under isostatic compression in high pressure conditions, all that air is compressed until it occupies no space. When we decompress and unload the product from the machine, we can realize that such product could not possibly have enough “plasticity” or “compressibility” as to go back to its previous volume and shape. All that air that was originally inside of the product, is now outside of it, occupying the volume around it, inside of the package.

Raw fresh meat

This topic is of considerable importance and though high isostatic pressure induces changes in the texture and color of raw meat, there are important potential and current applications in this space. We will focus on this question in a next entry of our blog. To open mouth, a few examples of current commercial applications with raw, never cooked meat:

•       Cargill Fressure ground beef
•      Zwanenberg Filet Americain and Leverwurst
•      Research on Innovative HPP meats and Marinated Meats