Article Written By Roxanne Stone MSc – Dogs Naturally Magazine
Keeping your dog safe from disease is a high priority for every dog owner, and the last thing you want is to poison your dog with bacteria that may be lurking in his raw diet. You may even hesitate to feed your dog a raw diet because of safety concerns.
So … buying a brand that uses high pressure pasteurization (HPP) might sound like a good idea.
I’ll explain the HPP process a little later … but the purpose of HPP is to eliminate risky bacteria (like Salmonella or Listeria) in the food. It’s touted as a great solution for high quality, safe, raw commercial pet foods. If your veterinarian is uncomfortable with the idea of you raw-feeding your dog, she may try to steer you towards HPP foods to protect your dog from scary bacteria.
But HPP isn’t all it’s cracked up to be … there are some drawbacks you need to know about before you decide to give your dog HPP foods.
I’ll tell you why it’s not the best way to protect your dog from food-borne pathogens. But first, here’s some background on how HPP was “sold” to the pet food industry…
Why Raw Pet Food Manufacturers Use HPP
There’s a lot of fear-mongering about raw pet food … you’ll hear it from kibble manufacturers, TV and newspaper stories, conventional veterinarians and of course the FDA (US Food and Drug Administration). The FDA warns consumers about pathogens like Salmonella and Listeria monocytogenes, which they say could not only put your pets at risk of disease, but also your human family members.
HPP is a patentable technology so there’s money to be made from encouraging consumers to buy HPP products. And there’s a benefit to the manufacturer and marketer who can claim their foods are safer than other raw pet foods. No company wants to be responsible for poisoning you or your pets.
But the real reason for the growing use of HPP is the FDA’s Food Safety Modernization Act (FMSA).
Food Safety Modernization Act (FMSA)
FMSA was signed into law by President Obama in January 2011. The act was an attempt to take a more proactive approach to food safety issues, focusing on prevention.
Before FMSA, the FDA didn’t do anything about food safety issues until they happened … for example, the melamine-tainted pet food that sickened or killed thousands of pets in 2007 wasn’t investigated by the FDA until after the fact, in 2008.
Manufacturers started to panic when they knew FMSA was coming, even though the FDA isn’t forcing any manufacturer to sterilize or pasteurize their foods.
In fact, an FDA document called Guidance for FDA Staff on salmonella in foods for animals states that it “Contains Nonbinding Recommendations” and represents the FDA’s “current thinking on this topic.”
Nonetheless, FMSA sent manufacturers rushing to HPP and the practice is far more common than it used to be, despite its shortfalls … and the fact that there have been very few cases of salmonellosis in humans from pet foods.
History Of Salmonella In Pet Foods
The CDC (Centers for Disease Control and Prevention) has reported only two instances in the last 30 years of humans contracting salmonellosis from pet foods … and both those instances were from dry kibble:
- Dry Pet Food (2012) – Diamond Pet Foods, Gaston SC, Salmonella infantis, 49 people affected in 20 states (2 in Canada), 10 hospitalized, no deaths reported
- Dry Pet Food (2007) – Mars Pet Care, Pennsylvania facility, Salmonella schwarzengrund, 62 people affected, 10 hospitalized, no deaths reported
There have been no Salmonella outbreaks associated with any brand of commercial raw pet food.
The FDA even tested 78 samples of raw pet foods (35 frozen, 31 freeze-dried and 12 dehydrated) and found only five samples contained Salmonella and/or Listeria monocytogenes.
It’s important to note a few things about this sample testing:
- Just because they found salmonella in the samples doesn’t mean they’d make people sick. The science isn’t that simple and there are many variables. The tests are very sensitive and can pick up minute amounts of bacteria … even one viable cell. And they don’t distinguish between different types of Salmonella, some of which are non-pathogenic.
- All the samples tested negative for E. coli and STEC (Shiga toxin-producing E. Coli). Both these are dangerous bacteria you don’t want in your dog food. These negative tests suggest that most raw food manufacturers use high quality meats that have been USDA-inspected. It’s highly unlikely you’d find these pathogens in USDA-inspected meats.
- Of the five samples that tested positive, four were from frozen foods and one from freeze-dried food.
- None were from dehydrated food … but then I question whether dehydrated food can be defined as raw since it is dehydrated to the point of shelf-stability.
- All food recalls that occurred after this testing were voluntary and no manufacturers were required to recall their foods.
So, with that background showing that raw pet foods don’t pose a high risk either for dogs or the humans they live with, let’s review what actually happens in the HPP process.
The HPP Process
HPP isn’t just for pet foods. It’s used to prevent spoilage and extend the shelf life of many common grocery store products like guacamole, juices, hummus or fruit purees.
Here’s what happens during the HPP process:
- The final packaged product is placed into a vessel of water
- The vessel may also contain oil or propylene glycol to keep the equipment lubricated (but it doesn’t touch the food in its packaging).
- The food is subjected to a high level of isostatic pressure (300–600MPa (megapascals) or 43,500-87,000 psi), transmitted by water.
These are extremely high pressures that disrupt the cell membranes of microorganisms in the food. They die and viable cells can’t survive. While HPP kills bacteria in the food, it does not kill spores. I’ll explain this later.
To understand the amount of pressure applied to HPP foods, consider that it’s five times the pressure at the deepest place on earth … the Mariana Trench, nearly 11,000 meters below sea level and deeper than Mount Everest is tall.
So when HPP marketing says it’s a “natural” process … how can it be, when there is nothing on earth with that kind of pressure?
And what does that extreme pressure do to the food?
Problems With HPP
Companies marketing HPP claim that while the HPP process kills bacteria, it doesn’t affect the nutrients, flavor or color of the foods. But there are studies showing these claims just aren’t true.
Here are five problems (and one advantage) I’ve found in researching HPP and what can happen to foods subjected to it.
1 Loss Of Nutrients
We know that heat reduces nutrients in foods. What happens with HPP?
George Flick Jr, PhD, University Distinguished Professor Of Food Science and Technology at Virginia Tech University, is a recognized authority in HPP. In his publication Thought and Substantial Lab Research Required: High hydrostatic pressure processing has potential in the meat industry (Fleischwirtschaft International, Journal for meat production and processing, ISSN 0179-2415, No 3, 2009), Dr Flick states:
“Basically, the effect of high pressure on microorganisms and proteins/enzymes was observed to be similar to that of thermal processing.”
Yet HPP proponents insist that the food is still raw after the HPP process. The discrepancy may lie in the definitions published by AAFCO (the Association of American Feed Control Officials). AAFCO defines “raw” as “food in its natural or food state, not having been subjected to heat in the course of preparation of food.” Because heat is specifically mentioned, many consider that HPP doesn’t “cook” the food.
In fact, in HPP there’s a 5.5°F rise in temperature for every 100 MPa and HPP is performed at 300 to 600 MPa. HPP food looks cooked on the surface – and it is!
2 Lipid oxidation
Lipid oxidation is a known negative effect of the HPP process. There are several research studies showing that high pressure treated samples oxidize more rapidly.
Lipid oxidation means the fat in the food becomes rancid, making it potentially toxic to your dog. In humans, studies have linked lipid oxidation to disease states such as atherosclerosis, IBD and kidney damage.
This lipid oxidation may be due to the cooperative effect with the denatured protein in the meat. We know that HPP denatures protein and there are many associated chemical reactions that aren’t fully understood.
3 Organic Foods Can Be HPP
Because HPP is considered a “natural” process, it can be used for organic foods. So if you’re buying an organic raw dog food, don’t assume it’s fresh and natural … because it could be high pressure pasteurized.
4 Potential Transfer Of Phthalates To Food
Phthalates are chemicals compounds in food packaging and they are known endocrine disruptors, linked to thyroid issues and obesity in both pets and humans. Because the HPP process is performed in the packaging, it seems likely that phthalates may be transferred to the food during processing. Phthalates are very fat soluble so the fat in meat makes the tendency for migration more likely.
There are no studies suggesting this happens … but neither are there any studies saying it’s safe. And we know that phthalates can be transferred during heating or freezing, so it seems logical to conclude the same thing may happen when you apply 87,000 lbs of pressure!
A joint 2011 study into HPP benefits and limitations by three universities in Spain, the US and Mexico found “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.”
5 Spores Are Not Inactivated
I mentioned this earlier … some spore-forming organisms like Clostridium botulinum (responsible for botulism poisoning) are not eliminated by HPP. 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.”
The FDA is aware of this problem and doesn’t consider HPP a valid process for higher pH foods. Spores are common in meat and seafood.
There are some potential benefits to HPP. Some studies show that vitamin C is retained at higher percentages and carotenoids are concentrated at greater levels after HPP.
But the information is quite inconsistent, varying even within one study (like the joint study mentioned above). Several studies were done on juices and fruit purees, and the information was then extrapolated into meats. That’s a big no-no in research … you can’t assume what happens to one food is the same for another.
HPP Isn’t Foolproof
By now you can see some of the drawbacks to HPP, including the fact that it isn’t foolproof. For example …
- Dangerous spores like Clostridium botulinum can still exist after HPP processing
- Of the companies whose food tested positive for Salmonella and/or Listeria in the FDA sample tests, some were using HPP already
So HPP isn’t it’s not really working, despite an equipment cost of $0.5 to $2.5 million, which you, the end user, pay for in higher raw food prices!
And when you pay for HPP products, you’re paying more but buying an inferior product that’s not really raw, but “cooked” … using pressure instead of heat.
What’s The Solution?
My advice is to avoid HPP foods for your dog.
In a healthy dog, the digestive system is designed to digest raw, even 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.
In fact, you may have noticed, dogs can happily digest all kinds of things that would make us humans ill. Think about rotten animal carcasses, ancient bones they dig up, all kinds of animal poop, water from a filthy puddle or pond, even their own vomit … you name it, they suck it down and don’t seem to suffer any ill effects. And let’s not forget routinely sniffing other dogs’ butts (just where the Salmonella bacteria are likely to linger after a dog poops).
How To Keep Your Dog Safe
Make sure you support your dog’s healthy digestive system so that his natural defenses can handle Salmonella and other bacteria.
- Feed a whole food, raw meat based diet, avoiding carbohydrates.
- Feed meat from grass-fed, free-range animals, which are less likely to contain pathogenic bacteria than unhealthy factory-farmed animals confined in crowded, dirty pens and highly stressed.
- Give probiotics to support balanced gut bacteria (adding some raw kefir or fermented vegetables to his diet is a great way to do this).
- Minimize vaccines and avoid antibiotics or other pharmaceutical drugs that can destroy healthy gut bacteria and weaken the digestive system.
- Always give filtered or spring water, not straight tap water.
If you’re buying a commercial frozen raw food:
- Find out if your brand uses HPP. HPP isn’t disclosed on the food label, so you’ll need to call the manufacturer of your brand to find out. Some companies will use HPP for higher risk proteins like poultry, but not for other meats, so ask about specific proteins.
- Don’t assume that because your dog’s food comes with multiple stacked patties in a bag, it’s not HPP. Some companies will HPP the food, then open the packaging and regrind the food before repackaging it. This opens up the risk of post-processing contamination and is a bad idea from a food safety standpoint.
- HPP equipment is expensive, but don’t assume only larger companies can afford to do it. Smaller companies are less likely to use HPP, but they may send it out to another company for HPP processing.
- If your dog is immune compromised … you may find your veterinarian prefers HPP foods for immune-compromised animals. My preference is to lightly cook your dog’s food instead of buying HPP food. You’ll lose some nutrients through cooking but you’ll avoid the unknown risks of HPP.
And now … give your dog a nice raw meal. Then wash your hands … for at least 20 seconds with soap and water, according to the FDA’s advice.