Quick Answer: High pressure processing (HPP) is a non-thermal pasteurization method that subjects sealed food to pressures of roughly 600 megapascals (about 87,000 psi). The pressure inactivates pathogens such as Listeria and Salmonella while leaving flavor and nutrients largely intact. It extends shelf life without heat, but it does not sterilize food, so refrigeration still matters.
High pressure processing sounds like a lab curiosity until you see it running. In a Nebraska lab, packaged pet food goes into a small tub, which is then lowered into a chamber that squeezes it with extraordinary force. Mary-Grace Danao, an associate research professor in the Department of Food Science and Technology at the University of Nebraska–Lincoln, described the pressure in comparative terms: six times the pressure at the Pacific Ocean's deepest point. That scale is why HPP has moved from research bench to production line across human and pet food.
What HPP Actually Does to Food
HPP works through isostatic pressure. The force acts equally on every surface of a sealed package, so the process doesn't depend on shape or the geometry of the food the way heat transfer does. Pathogens and spoilage organisms have cell membranes and proteins that deform under that pressure, and the damage stops them from reproducing.
Here's the part many marketing pages skip: HPP is a pasteurization step, not a sterilization step. Bacterial spores, the tough dormant forms produced by organisms like Clostridium botulinum, are largely resistant to HPP at typical settings. That's why HPP products still need cold chain storage. When a manufacturer says "shelf life extended," they mean the pathogen load has been reduced enough to make refrigerated shelf life longer, not that the product can sit on a warm shelf.
The upside is that heat-sensitive qualities survive better than they do under thermal pasteurization. Vitamins, color, and fresh flavor are less affected because the process doesn't rely on temperature. That tradeoff is why HPP has become attractive for juices, guacamole, and now raw pet food.
Why Raw Pet Food Is Driving Demand
Raw and minimally processed pet food is the fastest-growing segment of the pet food industry, according to the university's account of the research. Owners want fewer fillers and less processing. The problem is that raw products carry real pathogen risk for both animals and the people handling them.
HPP offers a middle path. It can reduce bacterial loads like Salmonella and Listeria in finished packaged food without cooking it. That's why Danao's lab has become a go-to reference point. The university's Food Processing Center has a Biosafety Level 2 (moderate-risk) designation, which allows researchers to inoculate food with a target virus or bacterium and then determine the exact HPP parameters needed to eliminate it.
This is where most guides go wrong. They treat HPP settings as universal. They aren't. Pressure level, hold time, temperature, and the food matrix all interact. A high-fat pet food and a high-moisture meat product can need different parameters to hit the same log reduction. Product-specific validation is what separates a credible HPP program from a box a manufacturer ticks.
Dark-Cutting Beef: Turning a Quality Problem Into a Product Option
Dark-cutting beef is one of the more surprising applications. The condition happens when cattle are stressed before slaughter, depleting glycogen and leaving the meat with a dark, purplish color. Consumers tend to read that color as spoilage, even when the meat is safe, so it's often discounted or diverted to lower-value uses.
In a paper published in Applied Food Research, Danao and colleagues showed that HPP at specific settings can shift the meat's appearance toward a normal-looking color while keeping nutritional value and texture. That matters because a meat product that moves from discount to standard shelf space changes the economics for a processor.
The catch is that appearance-enhancing treatments raise labeling and regulatory questions, and any processor using this approach would need to validate it against their own supplier and grading specifications. The study is a proof of concept, not a blanket license to sell dark-cutting beef as standard product.
Avian Influenza and the Cat Problem
Cats are unusually susceptible to avian influenza, and food is a central route of infection. Raw milk and raw or undercooked meat are the main concerns. Pet food is therefore a live safety question, not a theoretical one.
Danao is in discussions with Dustin Loy, director of the Nebraska Veterinary Diagnostic Center, and Hiep Vu, an associate professor of animal science who is internationally recognized in animal virology. Loy has framed HPP as "a potential robust enhancement for pet food safety," with the possibility of new products and economic impact for the state's agricultural and food systems.
Here's what makes this more than a press-release promise. Viral inactivation by HPP depends on the virus type, the matrix, and the process conditions, so each target needs its own validation. Before any manufacturer adds an HPP step to address a viral hazard, it should confirm the specific pathogen reduction with a challenge study run by a qualified lab.
Comparing HPP With Thermal Pasteurization
Choosing between HPP and heat treatment depends on what you're protecting. The table below summarizes the main tradeoffs.
| Factor | High Pressure Processing | Thermal Pasteurization |
|---|---|---|
| Primary mechanism | Pressure (about 600 MPa typical) | Heat (commonly 72°C for 15 seconds for HTST milk) |
| Effect on fresh flavor and color | Minimal change | Noticeable change in many foods |
| Spore inactivation | Limited; spores largely survive | Effective at higher temperatures and times |
| Packaging requirement | Flexible, sealed packages that withstand pressure | Heat-stable packaging |
| Typical use | Juices, guacamole, raw pet food, ready-to-eat meats | Milk, many shelf-stable foods |
The practical takeaway: HPP wins when quality and fresh character matter most and the product stays refrigerated. Thermal treatment still wins when you need shelf stability or spore control.
Where Education and Industry Meet
Research only matters if the people running plants can use it. Danao's outreach covers Nebraska Extension educators, veterinary students, and nutrition majors at the university. She also leads workshops for food industry personnel.
Frank Jimenez, CEO of Universal Pure, a Lincoln company that manufactures machinery for animal and human food, said the university's "expertise in food safety, HPP research and extension programs help move new ideas from the laboratory into practical applications." Rob Peregrina, director of Hiperbaric USA Corp., which supplies the lab's equipment, said the workshops "bridge the gap between the science of high pressure processing and its real-world application."
That gap is real. A plant manager who understands validation protocols, log reduction targets, and packaging compatibility makes far fewer costly mistakes than one who learned HPP from a vendor brochure. The Food Innovation Center is hosting a public open house on October 30, where attendees can see the research and equipment firsthand. Registration is available through the university's announcement.
Danao went further than cautious praise, saying: "Lincoln, Nebraska, truly is the HPP capital of North America." Whether or not you accept that label, the concentration of equipment and expertise within a short distance is unusual, and it's the reason people are now coming to Lincoln to learn the process.
Frequently Asked Questions
What is high pressure processing?
High pressure processing is a non-thermal pasteurization method that puts sealed food under very high pressure, usually around 600 MPa. The pressure disables pathogens and spoilage organisms without heat. HPP extends refrigerated shelf life and generally preserves fresh flavor, color, and nutrients better than heat-based methods.
Does high pressure processing kill all bacteria?
No. HPP reduces many vegetative bacteria and viruses, but bacterial spores generally survive typical HPP conditions. That's why HPP products still need refrigeration and proper cold chain handling. Any claim of sterility should be treated with skepticism.
How do you know what HPP settings a product needs?
Settings depend on the pathogen, the food matrix, pressure, hold time, and temperature. Manufacturers validate them through challenge studies, where a target organism is inoculated into the product and tested after treatment. Labs with the right biosafety designation, like the one at Nebraska's Food Processing Center, can run these tests.
Can high pressure processing help with avian influenza in pet food?
It may, which is why researchers are exploring it. Cats are highly susceptible to avian influenza, and raw or undercooked foods are a known route of infection. However, any viral inactivation claim has to be validated for the specific virus and product, so manufacturers should not assume HPP is a blanket fix.
Is HPP the same as pasteurization?
HPP is a form of pasteurization, but it works differently. Thermal pasteurization uses heat, while HPP uses pressure at or near room temperature. The result is a pathogen reduction that is often gentler on flavor and texture, though HPP does not achieve the same spore control as high-heat treatment.
Final Takeaway
If you're evaluating high pressure processing, the single most useful step is to ask for product-specific validation data before you commit. HPP can extend shelf life and protect fresh quality, but only when its parameters match your food and pathogen. Pass this article to someone managing a raw pet food or specialty meat line who's wrestling with that exact validation question, and ask them to request a challenge study from a qualified lab this month.