High Pressure Processing (HPP) offers clean label products with extended shelf-life without applying heat. This technology offers numerous advantages for a wide range of value-added products, but surely it has limits to its application and feasibility as well. Throughout this post, you will learn all about the products that are not compatible with HPP and the reason behind it.
High pressure processing (HPP) is a non-thermal technology that is suitable to ensure safety without altering the delicate nutritional and sensory characteristics of food. It is a hydrostatic process, where pressure is transmitted through water, therefore when the pressure encounters an ingredient it will be transmitted uniformly and homogenously throughout it, regardless of its shape and size.
Water Activity: An Essential Parameter to Succeed with HPP
It is recommended that foods have a water activity (aW) above 0.96 to maximize the lethal effect on microorganisms. In other words, HPP is more effective in high aW products because the product will have a higher content of free water available to transmit the pressure, leading to a higher microbial inactivation and extended shelf-life.
Based on the water activity content of ingredients, here are some ingredients that are suitable and not suitable under HPP:
What is not recommended
HPP can be applied to a wide variety of foods, from juices & beverages to ready-to-eat (RTE) meals and baby food, and many other applications.
It is important to note that not only the water activity of the products will influence the outcome, but also, the type of product and its formulation, since in some products some textural changes can occur, usually in the absence of a liquid or dressing surrounding them. This is the case of a salad, or chunks of fruit – it is recommended that this product includes a dressing or a surrounding liquid.
For example, Sandridge with their Grandma’s recipe line:
Having this account, here are the main ingredients to avoid when processing:
Spices, Powders, and Extracts
Any dry product such as powdered food matrices, extracts, and dry spices, is not a good target for HPP technology. Isostatic pressure needs water inside of the food product for its homogeneous, uniform, efficient transmission and consequently to cause inactivation of the microorganisms present in the product.
Dried Nuts or Fruits; Cereals
Similar to the abovementioned case, such products alone have a low water activity content. HPP is not effective in extending the shelf life or generally improving the safety of such products.
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 flexible, sealed formats… and then HPP it for shelf life and safety while maintaining its attributes.
However, it is not compatible for whole, raw fresh fruit. HPP will lead to changes in the texture and in the cell walls and change its typical aspect. We recommend to mix the chopped fruit with juice and process this product, this can have several advantages: the integrity of the chopped fruit will be maintained, the juice will enter the chopped fruit, resulting in new flavors and also the juice can have an acidic pH, or high content in antioxidant compounds and help to extend further the shelf-life.
Vegetable Leaves and Leafy Salads
As said before, 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, leafy greens appear mushier, more flaccid, and more exudative.
But again, can be a great solution for wet salads.
Bread & Pastries
The comments below apply to any product with a lot of trapped air, fluffy or with a mousse-like structure.
Basically, when a loaf of bread, or a croissant, is put through an HPP system, it will become a flat, collapsed piece of pastry. Why?
Loaves of bread and pastries have a huge amount of “empty spaces” in their matrix, which creates plenty of trapped air. Under isostatic compression in high pressure conditions, all that air is compressed until it occupies no space. Such a product cannot possibly have enough “compressibility” 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.
When in doubt, ask our HPP experts
Finally, it is important to note that we discuss ingredients that usually do not work under HPP. However, Hiperbaric invites you to try and see how your product will behave under pressure. For that, we have our HPP Incubator and a team of experts that are glad to assist you. If you have any doubts, do not hesitate to contact us.