Interviews

UHPT: “The Fields of Application for the High-Pressure Process Are Very Extensive and Continue to Grow”

Uhde High Pressure Technologies (UHPT) is a high technology subsidiary of German multinational conglomerate thyssenkrupp. Founded in 1930, it is one of the world’s leading companies for industrial high-pressure systems and equipment, with an international customer base in several markets.

UHPT serves customers along the entire plant life cycle, from the planning phase with in-house engineering to the operation phase with service and spare parts supply. The company combines local manufacturing at its premises in Germany with a global supplier network to ensure high quality at optimized costs. Qualified supervisors support installation and commissioning worldwide, along with customer support over the entire service life of the machines.

We spoke to Boris Brockhaus, Product Manager HPP at UHPT, to find out about the applications of high-pressure technologies in the production of plant-based foods.

© UHPT

Which vegan products can be treated using the high-pressure process (HPP)?
The most common application for the HPP process is vegan products such as fresh fruit or vegetable juices. Another large segment is purees (e.g. guacamole or hummus), soups (e.g. gazpacho or vegetable stew), dips (e.g. sauces or dressings), and flavored or infused drinks (e.g. cold brew coffee/tea or infused water). Meat and dairy alternatives, such as extruded plant proteins from peas and cereals or soy products, are also a rapidly growing segment.

For example, vegan burger patties, sausages, schnitzel, sliced meat, or bacon can be treated very well. HPP also has a beneficial effect on products such as almond milk, oat milk, and soy milk, as there is no heat influence. Some new alternatives such as vegan fish or vegan eggs are already being investigated. Another application is products made from algae, such as spirulina or chlorella, which are added as biomass to certain products before or after the HPP process.

“[HPP] is a process that contributes to ensuring food safety and reducing recalls”

The HPP process has a minimal effect on color and antioxidants, but the shelf life of the product can be extended from two to three days to up to three months. In addition to germ reduction and shelf-life extension, HPP can also be used to stop fermentation processes, which is helpful in order to maintain the desired properties of the products (e.g. kimchi), as well as denaturing any germs that may be present and increasing shelf life and safety. Another application is the use of HPP in unfiltered beer, where HPP also leads to a reduction in yeasts and germs. The fields of application for HPP are very extensive and continue to grow.

© UHPT

What advantages does the HPP process offer compared to conventional methods?
The major advantage of HPP treatment is the reduction of germs and the resulting extension of shelf life without thermal influence. This preserves the freshness, texture, and taste of the product. Ingredients such as vitamins, antioxidants, and nutrients, or even special enzymes, are only slightly affected and therefore offer almost the full value of a fresh product. The use of preservatives is also not necessary — the product remains free of chemicals, and this is achieved solely using physics.

As the product can be treated directly in its final packaging, there is no subsequent contamination. During the pressure treatment, the pressure acts directly and evenly on all areas of the product, in contrast to other processes where some areas (core) are treated sufficiently but others (surface) are treated too intensively or damagingly. It is therefore a process that contributes to ensuring food safety and reducing recalls in the food retail sector.

Some products cannot be thermally treated, as this would lead to changes in the protein structure or unwanted coloration; examples are guacamole and plant proteins. For these reasons, the HPP process is particularly suitable.

How does the process work?
The products are loaded in their final packaging into special treatment baskets, which are then moved into the high-pressure vessel before the system is closed. First, the vessel with the products is filled with water so that the remaining air can escape out of the vessel, then additional water is pumped into the vessel via external pressure intensifiers. When the pressure is increased, the water is compressed by around 17% and an additional 60 liters of water are injected into a 350-liter vessel to achieve a pressure of 6000 bar.

“The applications for the HPP process can be sustainable.”

During the dwell time, which can vary from product to product, the cell walls of the bacteria are damaged, and the bacteria are denatured. As the water serves as a pressure-transferring medium, the packaged products are pressurized homogeneously and gently from all sides; no shear forces are generated, and the product is not deformed. The pressure is then released, and drops to atmospheric level. The machine then opens, and the treated products are pushed outwards on belts so that the goods can be unloaded from the treatment baskets.

© UHPT

What are the economic factors for the HPP process?
The capacity of a machine is mainly influenced by the filling degree. This can vary from 30% for small bottles to up to 80% for large batch packaging (process bags). With a high-pressure vessel of 350 liters, this means between 105 and 280 liters per cycle. The cycle time again depends on the product and the resulting dwell time, which can vary between two and nine minutes depending on the pre-contamination, the pH value, and the water activity. For microorganisms such as mold or yeasts, lower pressures are sufficient, while germs such as pathogenic listeria, E-coli or salmonella must be treated at up to 6000 bar, which is also reflected in the pressure build-up time. Depending on the machine size, treatment volumes of a few tons up to 25 tons per day can be achieved.

“Raw goods which would not even reach the market without HPP can be processed into purees or juices”

The costs of the process can be divided into investment and operating costs. Water consumption, electricity consumption, employees, service, and wear parts are all considered. As the machine must withstand enormous forces over many thousands of treatment cycles, worn parts should be replaced regularly to ensure uninterrupted production. The largest proportion of energy in a cycle is required to increase the pressure, with the pressure intensifiers working for around three minutes to pump the corresponding amount of water into the 350L vessel. A total cycle then has an energy consumption of around 17 kWh. In comparison, almost twice the amount of energy would be required to heat the corresponding amount of water from 5° to 80°C. Depending on the degree of utilization, the total costs for the HPP process are between €0.10 and €0.15 per liter.

Is the HPP process sustainable?
The applications for the HPP process can be sustainable. On the one hand, the shelf life of fresh products, which would only have a short shelf life without HPP, can be extended — which can reduce wastage and rejection of goods. On the other hand, raw goods (e.g. ugly fruits or overproduction), which would not even reach the market without HPP, can be processed into purees or juices, treated with HPP, and marketed with a longer shelf life. Additives that are reduced during heat treatment do not need to be added to the products, as they have not been reduced by the HPP process on the original product.

The HPP process itself is also sustainable. Drinking water is used for the treatment, which is largely reused thanks to the integration of an intelligent water system that detects and analyzes the water quality. Hot water generated by the pump cooling or during compression can be collected and fed into a heating system, or at least used for cleaning.

As the machine is powered by electricity and not gas, this can of course be fed in from green energy. Contaminated wastewater or exhaust gases are not produced.

© UHPT

Are there any disadvantages compared to other processes?
HPP treatment is a germ reduction process, so depending on the pre-contamination, the germs are reduced by log4 to log5, similar to pasteurization, depending on the product. Some spores are not denatured during the process, which is why the products must remain in the cold chain after treatment to ensure an adequate shelf life. Due to the investment and the requirements for the installation site (floor load, machine size, cold rooms, and power connection), an installation must be planned in detail and agreed upon with all parties involved in advance.

Only products with a high to low water content can be used for the HPP process; dry products such as powder or products with an air content such as bread do not work, as the pressure in the product cannot be transferred or the air is forced out of the product.

However, if the advantages are set against this, including the fact that some products can only be treated with HPP if thermal energy and chemicals are dispensed with and the quality and safety of the product are to be increased even further, the decision is clear.

How can you test whether the process is beneficial for selected products without your own plant?
UHPT offers the possibility to test your products in our application center in Quakenbrück with food technologists. Some tests and analyses can already be carried out at the site itself, and further shelf-life studies can then be carried out with local institutes. In addition to the influence of high pressure on the product, UHPT also provides support in the choice of packaging. The packaging is an essential component, as it must be flexible and impermeable to water in order to withstand the compression of 17%, even more so if it is MAP packaging. Once the product has been developed, UHPT provides support with toll processing, whereby the customer can have its products processed by UHPT at the Quakenbrück site up to a capacity of 25 tons per day before making its own investment.

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