High-pressure processing (HPP) offers a valuable solution for preventing spoilage in fresh packaged food products, preserving quality without resorting to heat or chemicals.
In this article, we explain what HPP is, how it works, and how it can help boost shelf life while protecting taste, nutrition, and texture.
What Is High-Pressure Processing?
HPP is a food preservation technique that employs high pressures to kill or deactivate many of the microorganisms that cause spoilage without affecting taste, texture, aesthetics, or other important properties. It is best employed with products that will be refrigerated after final packaging.
HPP is recognized by US food regulators as a valid process for guaranteeing food safety for compatible food products. Example guidance includes:
- U.S. Food and Drug Administration (FDA) guidelines for juice.
- U.S. Department of Agriculture Food and Safety Inspection Service requirements for meat, poultry, and processed egg products.
Other terms sometimes used to describe this process include:
- High-pressure pascalization
- Cold pasteurization
- High hydrostatic pressure processing
- Ultra-high pressure processing
HPP Process: How Does High-Pressure Processing Work?
HPP is a non-thermal process, which means that it operates in temperature conditions below 100°F.
High-pressure processing relies on cold water to transmit high isostatic pressure levels (from 58,000–87,000 PSI) instantaneously into packaged food. This pressure is held for several minutes, killing microorganisms and deactivating enzymes and spores without resorting to high heat as in traditional approaches such as pasteurization. Water compression in the HPP process will cause temperatures to rise, but by less than 40°F at even the highest requisite pressure levels. Foods rapidly return to a normal temperature after the process is completed.
Removing food-destroying pathogens is a highly effective method for slowing down the processes that cause food to decay over time. Because it does not rely on chemicals, added preservatives, or heat, HPP is an ideal method for boosting shelf life without harming the quality or taste of the food inside.
HPP Machine Design and Process
An HPP machine is used once food products have already been packaged (typically in their final in-store packaging).
- Specially designed basket-like containers are used to house packaged food products during the pressurization process.
- The containers are pushed into a high-pressure chamber where they are submerged.
- A hyperbaric chamber is brought up to the requisite pressure levels and held for 2–6 minutes, depending on requisite process parameters.
- The containers are removed from the HPP machine and drained.
Precise process parameters vary depending on variables such as the water activity, acidity, and fat content levels of the food being processed.
The packaging employed must be flexible enough to withstand compression during pressurization, elastic enough to regain its shape when the process is complete, and waterproof to withstand submersion. For this reason, plastic containers are the most common choice for HPP packaging. Polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP) are all examples of commonly used, HPP-compatible materials.
Learn more in our guide to Plastic Packaging for Food and the Science of Shelf Life
Important Benefits of High-Pressure Processing for Food Packaging
HPP has become an increasingly popular choice for fresh food packaging due to its broad benefits for consumers:
- Improved shelf life. HPP inactivates pathogens like bacteria, viruses, mold, and parasites. While different organisms have varied degrees of pressure resistance, HPP-treated food can generally increase shelf life by two to three times compared to non-pressurized fresh foods. Because many factors impact shelf life, we recommend that manufacturers validate shelf life for their specific products.
- Reduced preservatives to improve taste and bring fresh-tasting food to customers.
- Preserved nutrition. The pressurization process has a minimal impact on antioxidants, vitamins, and other nutrients compared to heat-based processes, preserving healthful content.
- Protected aesthetic qualities. By avoiding heat, HPP helps preserve the compounds responsible for the subtle flavors and aromas of fresh food and maintains texture.
HPP Applications
High-pressure processing can be used to boost the shelf life of a huge variety of packaged food products. Representative examples include:
- Guacamole, salsas, wet salads, and other plant-based dips and snacks
- Milk, fruit juices, smoothies, and other beverages
- Sliced deli meats, marinated meats, and raw meats (raw meat will undergo a color change but appear identical after cooking compared to non-HPP meat).
- Seafood, where HPP can assist with processing tasks like extracting meat from lobsters, crabs, and mollusks.
- Dairy products like cheese, yogurt, cottage cheese, and sandwich spreads.
- Baby foods, fruit purees, jams, and other submerged or semi-liquid fruit or vegetable products.
- Unfrozen pre-prepared meals.
Limitations of High-Pressure Food Processing
While high-pressure processing is a proven solution for a wide range of food and beverage products, it is not the right choice for every application. In general, HPP is most effective for products that are suspended in a liquid, dressing, or sauce.
The most important limitation of high-pressure processing is that it is not suitable for extremely dry products or frozen foods. Specifically, HPP cannot be employed with foods with a water activity level (aw) less than .8. A water activity level close to one is necessary to maximize the effectiveness of the HPP process. HPP should also not be employed with products with air pockets (like baked goods), which can deform under pressure. Finally, in certain raw meat and egg products, HPP may cause a change to texture or color, but not flavor. This effect does not extend to marinated meats.
Unless combined with heat treatment, HPP does not ensure the permanent sterilization of spores or deactivation of enzymes, so it is not suitable for products requiring a room temperature shelf life of months or even years. However, HPP combined with refrigeration provides a highly effective solution for preventing spore germination.
What to look for in HPP-Compatible Food Packaging
The right packaging is crucial to withstanding the rigors of the pressurization process. When sourcing HPP-compatible packaging, we recommend looking for vendors that can provide packaging with the following features:
- Wide flanges and a wide sealing surface to maintain a secure seal and avoid blowouts during pressurization.
- Strong sidewalls to help the container maintain its shape without damaging the food inside.
- A heavy-duty design that is resistant to cracking.
Need help finding the right packaging solutions compatible with high-pressure processing? Lacerta is here to help.
With over 30 years of experience in food packaging, we can help find the right solution for your HPP-related challenges and beyond. Our team is ready to help find the right packaging to boost your products’ shelf life while helping them look and taste their best.
We invite you to reach out to our team to discuss your food packaging needs
