High-pressure pasteurization (HPP) is a controversial topic when it comes to raw dog food.
You may be someone who says you’d never feed HPP food to your dog. Or perhaps it eases your concerns about risky bacteria in the food … like Salmonella, Listeria or E coli. Maybe your vet doesn’t approve of raw feeding, but feels better if you use a food that’s HPP.
There are many different views on HPP. So I want to explore the topic of HPP … and try to clear up some questions and misconceptions.
What Is High Pressure Pasteurization (HPP)?
You may be familiar with pasteurization, which uses high heat to control food pathogens. But high pressure pasteurization is different.
Most high pressure pasteurization doesn’t use heat. It’s a cold temperature method used to prevent food spoilage. HPP applies extremely high pressure to foods to manage bacteria. HPP Is also called high pressure pascalization or cold pasteurization.
And it’s not just used for pet foods but also many foods you probably enjoy yourself. Here are some grocery store products you might buy …
- Fruit purées, baby foods
- Dips like guacamole or hummus
- Sauces, dressings, salsas
- Pre-made meals, wet salads
- Meats (fresh and processed)
- Seafood (raw and cooked)
These are just a few of the foods that are usually high pressure pasteurized. So now you know why that guacamole you bought didn’t turn brown!
HPP Process For Raw Dog Food
In some cases, the manufacturer grinds, mixes and packages the raw ingredients. Then they HPP the packaged product. Some may even open the packaging and regrind the food before repackaging it. This may open up the risk of post-processing contamination.
In other cases, foods aren’t HPP’d in their final packaging. So (using clean rooms), companies may further process the foods. Other companies may dehydrate, air dry or freeze-dry the HPP’d product.
Here’s the actual HPP process:
- The product is put in hermetically sealed packaging.
- It’s placed into a “pressure vessel.”
- The pressure vessel is filled with cold water.
- High levels of isostatic pressure (300–600MPa (megapascals) or 43,500-87,000 psi) are applied (through the water) to the food.
- “Hold” times range from a few seconds to a few minutes.
To understand the amount of pressure applied to HPP foods … let’s compare it to the Mariana Trench. That’s the deepest place on earth. It’s nearly 11,000 meters below sea level and deeper than Mount Everest is tall. The pressure of most HPP foods is about 5 times the pressure in the Mariana Trench.
These extremely high pressures disrupt the cell membranes of microorganisms in the food. They die and viable cells can’t survive. But while HPP kills bacteria in the food, it doesn’t kill spores.
Spores Survive HPP
There are some spore-forming organisms like Clostridium botulinum (responsible for botulism poisoning in people). HPP doesn’t eliminate these. One study concludes:
“…spores of bacteria remain the most difficult problem to eliminate for making HPP-treated low-acid foods stable at room temperature. Eliminating all spores in a low- acid commercial food while maintaining non-thermal processing conditions is not possible at the present time.”
This happens because spores will become dormant during HPP, but often germinate later. This means that heat treatments like PATS (pressure-assisted thermal sterilization) is more effective for spores like Clostridium.
However, botulism or other Clostridium poisoning is very rare in dogs. So this is more of a risk for the owner handling the food. Wash your hands and you’ll be fine!
Toxins From Food Packaging
The main concern here is toxins that might leach from packaging into the food.
One study concluded,
“There is a need for further research on HPP effects on mass transfer processes between food, packaging films, and storage environment. […] The possibility of packaging components and packaging degradation substances formed during high temperature and pressure processing, transferring into foods where they can experience further chemical changes has to be investigated.”
But in general, research shows the pressures and hold treatment times used for raw dog foods don’t cause any transfer of packaging chemicals into the food.
If you buy HPP foods, ask the manufacturer about their packaging. Make sure they use BPA-free packaging materials. And ask them if they’ve tested the food for any leaching of chemicals.
HPP Isn’t Legally Required
HPP has become increasingly popular as a method of pathogen control since the Food Safety Modernization Act (FSMA) was introduced in 2011.
There’s no law requiring raw pet food makers to use HPP. But many of them have been forced into it.
Before FMSA, the FDA didn’t do anything proactive about pet food safety. For example, they didn’t investigate the melamine-tainted pet food that sickened or killed thousands of pets in 2007 until after the fact, in 2008.
And there are still no FDA laws about Salmonella or other bacteria in pet foods. There’s a July 2013 document called Guidance for FDA Staff on salmonella in foods for animals. It states that “FDA’s guidance documents, including this guidance, do not establish legally enforceable responsibilities.”
HACCP stands for Hazard Analysis and Critical Control Point. It’s a USDA enforcement program to ensure food safety and quality control. It requires human and pet food companies (raw and cooked) to maintain a detailed log of manufacturing processes, standards and tracking. It doesn’t specifically require methods like HPP.
But the FDA thinks raw food is dangerous. So they and some state Departments of Agriculture have pressured raw food manufacturers. And even though there have been serious salmonella outbreaks from contaminated kibble, not raw foods … they have targeted raw food manufacturers.
The FDA has applied a zero-tolerance policy to bacteria like salmonella or listeria in raw pet food. (That in itself is absurd since they allow salmonella in grocery store chicken for humans!).
They conduct frequent raw pet food plant inspections and sample-testing to find “adulterated” foods. They often force manufacturers into product recalls. They’re mostly worried about people getting sick from handling raw pet foods … or something like your dog licking your child’s face.
But there are no reported cases of bacteria in raw pet foods harming people or animals. Meanwhile, there are many cases of kibble contaminants harming pets … excess vitamin D and aflatoxins being two recent examples.
Still, it gets very difficult and expensive for raw manufacturers to deal with this constant onslaught. One well-known raw food manufacturer told us …
“After your first recall you get a target on your back and get retested over and over. There’s a huge amount of paperwork, and your plant is shut down while the Department of Agriculture is in your plant asking for information. Since we moved to HPP, all the salmonella tests have been negative.”
So … some manufacturers have resorted to using HPP for their raw foods. Some may only use it for higher bacteria risk foods like poultry. Some freeze-dried foods may also be HPP.
In some cases, manufacturers will tell you they’re using HPP. Others don’t mention it, so you’ll have to call them to find out. They’re not required to disclose HPP on their labels or websites.
I want to go over the effects HPP has on raw dog food. There’s been quite a bit of research on HPP for human foods, but the analysis isn’t straightforward.
Food Changes After HPP
One thing you need to know is how HPP changes the quality of your dog’s food.
The research can be confusing because some studies focus on human foods. So they use higher temperatures, longer hold times and higher pressures than raw dog food makers use.
Typical levels for raw food manufacturers are 600 MPa, with hold times of around 2 minutes and cold water temperatures.
Is It Still Raw?
Texture and color changes in HPP foods cause people to ask “is the food really raw?”
The answer is that it is … as long as heat wasn’t used during the HPP process. Some HPP processing is done with higher water temperatures. So ask the maker of your food about the temperatures they use for their HPP.
And here’s something else to think about. Is all your dog’s food really raw anyway? Veterinarian Marion (Meg) Smart DVM PhD asked that question at a panel discussion last year.
She pointed out dogs bury food and leave it incubating in the ground for weeks or months. When they eventually dig it up, is it really still raw? It’s certainly covered in mold and bacteria! The protein structure will have changed too.
At the very least, it’s fermented or may even be partly cooked from its warm underground stay. I also learned that some people who follow a raw or “living” food diet don’t eat fermented foods. Fermenting can make food appear “cooked” and change the texture and color.
In the wild, mother wolves eat food and regurgitate it for their cubs. Is it truly raw after it’s been exposed to powerful stomach acids?
These are just things to keep in mind when you consider the pros and cons of HPP food for your dog.
Let’s look at what HPP does to meat, since that’s the main ingredient in your dog’s raw diet.
HPP Effects On Meat
The main conclusion from studies of HPP on meat is that HPP may “denature” protein (ie take away its natural quality). This happens because HPP breaks down the protein molecules, which affects the myofibrillar structure of the meat. This means the muscle fibers are different than non-HPP meat.
But research also shows that the process changes the color and texture of meat more than nutrient value.
- It can give the meat a more gelatinous quality.
- It makes red meats like beef look lighter in color … almost as if cooked.
- It can make the meat more tender and digestible.
These changes are more important to people than to dogs, who usually aren’t too concerned about color or texture.
Several studies report that HPP makes meat more digestible. Because the structure of the protein is altered, it may mean digestive enzymes can break down the nutrients more readily.
And at least one raw pet food manufacturer has tested the bioavailability of their food after HPP. The research showed digestibility after HPP was …
- Protein 95.6%
- Fat 97%
- Caloric 96%
This data is encouraging and suggests your dog can still gain most of the nutritional benefits in the food.
Lipid (Fat) Oxidation
HPP does appear to increase fat oxidation. This is not during the HPP process but later, during storage. However, it’s less likely with raw dog foods because of shorter hold times, lower pressures and water temperatures.
Oxidation also varies depending on exposure to air during storage. Removing air from the bags and using vacuum packaging offers protection against oxidation. Keeping the food frozen may help slow lipid oxidation too.
Poultry like chicken or turkey may suffer more from lipid oxidation than other meats. Reducing the fat content in these foods helps lower the risk of oxidation.
If you feed your dog HPP foods, use extra care when thawing. Thaw the food in an airtight container to minimize exposure to air and thus fat oxidation.
Studies have focused a lot on vitamin C because HPP is used so much in juices and other fruit products. Vitamin C loss occurs more at higher pressure levels, with longer hold times (20 minutes or more compared to around 2 minutes for most pet foods). Also, alkaline foods are more susceptible to vitamin C loss.
One study looked at the effects of HPP on antioxidants and carotenoids in vegetables at 400 and 600 MPa. At these levels they found that “antioxidant capacity and total carotenoid content differed between vegetables but were unaffected by HPP treatment.” 600 MPa is the pressure used for most HPP dog foods, so it’s likely most important vitamins are still intact.
One raw pet food maker found that vitamin A deteriorated by about 20% after HPP. Pantothenic acid, pyroxidine and vitamin B12 were also lower. So the company has increased the amounts of liver and other organ meats, as well as muscle meats, to make sure they still meet AAFCO requirements for these nutrients.
Minerals, including important ones like calcium and phosphorus, appear to be minimally affected by HPP.
In fact, a manufacturer review found that some minerals actually increased slightly during HPP.
Live enzymes are one of the reasons to feed your dog a raw diet. So you want to know whether enzymes are damaged during HPP.
One study found that pressures of 800 MPa or more, longer hold times (up to 45 minutes) and warm temperatures (25 to 60 degrees Celsius) increased the inactivation of food enzymes. At water temperatures under 45 Celsius, they found no impact on enzymatic activity.
At the lower pressures, water temperatures and hold times used in raw dog food, it appears enzyme loss in the food is minimal. This conclusion has been confirmed by at least one manufacturer’s testing of their own foods.
Generally, nutrient losses during HPP appear small at the pressures and hold times used for raw pet foods.
A 2011 joint Mexican-Spanish-US study of different HPP research concluded,
“In general, HPP causes no significant losses of functional compounds in foods, and often HPP has been to induce much lower losses than conventional thermal processes. [ … ] Additional research is required on important compounds such as vitamin E. Polyphenols seems to be favored by HPP treatments and in some cases HPP may increase their availability. Studies performed on antioxidant activity are few and contradictory. This may reflect the diverse methods used to quantify antioxidant activity in different foods.”
But … should you use HPP foods for your dog?
Should You Feed HPP Foods?
Well, first of all, you may not have much choice.
Many raw (and raw freeze-dried) food manufacturers are using HPP. Some may use it just for higher bacteria foods like poultry. But it can be hard to find a brand that doesn’t use HPP … and isn’t suffering the effects of frequent inspections and testing by government officials.
Personally, based on the research I’ve read, I’d be comfortable feeding HPP foods to my dog. Although I don’t worry about bacteria, the FDA does … and so do some conventional vets.
And of course, I eat quite a lot of foods myself that I now know have been high pressure pasteurized. And frankly, I’ve never stopped to consider whether my hummus, soup or salsa is less nutritious!
If you want the peace of mind of knowing your dog and your family are safer, HPP foods offer a big advantage. And they offer peace of mind for the manufacturer too … not having to worry about bacteria in their foods harming pets or people.
The biggest factors with changes in raw dog food after HPP are related to the texture and color of food. These are things people care about, but dogs don’t usually mind.
Even still … there are some questions to ask the manufacturer to make sure you’re getting a high-quality product.
Questions For Food Manufacturers
Of course, the first question is …
- Do you use HPP?
Some may not make the information easily accessible. So you might have to do some digging or make some phone calls. Be prepared to read between the lines. Many companies send their foods out to be HPP’d. Then they can say “we don’t HPP our foods” … technically not a lie!
Personally, I’d rather choose a company that’s honest and open about their processes and the reasons for them.
Then, ask about the specific process.
- What pressure, water temperatures and hold times does your HPP process apply?
Ideally you should expect pressure of up to 600 MPa, cold water, and hold times of around 2 minutes. If warm or hot water is used, then your food may not be truly raw.
The next few questions are important if you want to make sure your dog is getting sufficient nutrients.
- Have you tested the nutrients in your food after the HPP process?
- Have you made changes to compensate for any nutrient losses?
- Is your Guaranteed Analysis label based on nutrients after HPP?
With respect to the risk of fat oxidation …
- Do you add antioxidants to prevent lipid oxidation?
- Do you remove oxygen from the packaging before sealing?
- Is food vacuum-packed or at least in airtight packaging?
And finally, to be sure your food is chemical-free…
- Do you use BPA-free packaging?
- Have you tested for any leaching of chemicals into the food after HPP?
These are all things I’d want to know before deciding to use a food that’s been high pressure pasteurized. As always, it’s important to do your research to make sure your dog’s getting what he needs.
But what if you absolutely don’t want to use HPP?
Are Non-HPP Raw Foods Risky?
For most dogs and dog owners, no. Many raw feeders have been feeding non-HPP foods … including homemade raw foods … for decades. And it’s very rare that they or their families or dogs have any problems.
Healthy dogs’ digestive systems can efficiently digest raw meat. They can even handle spoiled or contaminated meat. Dogs have highly acidic stomachs as well as natural digestive enzymes and bile that help them process Salmonella and other bacteria without becoming ill. So they’re not prone to illness from these bacteria.
In fact, you may have noticed, dogs can happily digest all kinds of things that would make us humans ill. Rotten animal carcasses, ancient bones they dig up, all kinds of animal poop, water from a filthy puddle or pond, even their own vomit. Most dogs don’t suffer any ill effects.
As I mentioned earlier, what the FDA is worried about is you or your family getting sick from bacteria. But they haven’t found any cases of raw dog food causing illness.
We know how to handle meat for ourselves … and it’s not any different when we handle dog food. Remember … even the FDA allows grocery store chicken for people to contain Salmonella!
So wash your hands and clean your cutting boards and counters thoroughly.
How To Keep Your Dog Safe
Feeding HPP foods is obviously one option. And because so many manufacturers are using HPP, you may not have much choice when you buy pre-made food.
With HPP food, you’ll minimize bacteria risk to your dog and your family. And, as long as you buy from a reputable company, your dog will get all the nutrients he needs.
But … whatever food you give your dog, support his healthy digestive system so that his natural defenses can handle bacteria.
Feed the best quality meats you can. If possible, give meat from grass-fed, free-range animals. They’re less likely to contain pathogenic bacteria than unhealthy, stressed, poorly-fed factory-farmed animals confined to crowded, dirty pens.
Find a food that doesn’t use synthetic vitamins and minerals. Raw food ingredients should stand on their own.
Give probiotics to support balanced gut bacteria.
Always give filtered or spring water, not straight tap water.
Whether you choose HPP food or not, always be sure you understand your manufacturer’s ingredient sourcing and processing practices. I’d like to leave you with a quote from animal nutritionist Richard Patton PhD:
“The FDA purports to have reason to consider raw as more of a risk than dry pet food. That’s their position. I counter that any pet food, including raw, is safer than human food, based on the FDA’s own publications. HPP or not? This would appear to be an irrelevant question, as regardless of your preference, the choice is getting hard to find. Lost in all the hand wringing and noise is a simple reality: The most foolproof way to minimize the chance of your pet’s food being contaminated is to buy from a reputable company that meets government certification criteria, procures high quality ingredients and is obsessive about proper manufacturing.”
As always … get to know your supplier!
[FDA Announcement] Food Safety Modernization Act (FSMA). Updated 1/4/21.
[Guidance For FDA Staff] Compliance Policy Guide Sec. 690.800 Salmonella in Food for Animals. 12 Jul 2013.
Simonin H et al. New insights into the high‐pressure processing of meat and meat products. Comprehensive Reviews In Food Science & Safety. May 2012;11(3):285-306.
Messens et al. The use of high pressure to modify the functionality of food proteins. Trends in Food Science & Technology. 1997;8(4):107-112.
Black EP et al. Response of spores to high pressure processing. Comprehensive Reviews In Food Science & Safety. Oct 2007;6(4):103-119.
Gould H et al. Clostridium difficile in food and domestic animals: A new foodborne pathogen? Clinical Infectious Diseases. Sep 2010;51(5):577–582.
[FDA Notice] HACCP principles and application guidelines. Updated 12/19/17.
Escobedo-Avellaneda Z et al. Benefits and limitations of food processing by high-pressure technologies: effects on functional compounds and abiotic contaminants. Journal of Food. 2011;9(4):351-364
Kaur L et al. High pressure processing of meat: Effects on ultrastructure and protein digestibility. Food Funct. 2016;7:2389-2397
Soyer A et al. Effects of freezing temperature and duration of frozen storage on lipid and protein oxidation in chicken meat. Food Chemistry. 2010;120(4):1025-1030.
AMARAL, Beatriz A et al. Lipid oxidation in meat: mechanisms and protective factors – a review. Food Sci. Technol. 2018;38:1-15.
Seyderhel I et al. Pressure induced inactivation of selected food enzymes. Journal of Food Science. 1996;61(2).
Chakraborty S et al. High‐pressure inactivation of enzymes: A review on its recent applications on fruit purees and juices. Comprehensive Reviews In Food Science & Safety. 2014;13(4).
Oey I et al. Does high pressure processing influence nutritional aspects of plant based food systems? Trends in Food Science & Technology. 2008;19(6):300-308.
McInerney JK et al. Effects of high pressure processing on antioxidant activity, and total carotenoid content and availability, in vegetables. Innovative Food Science & Emerging Technologies. 2007;8(4):543-548.