HPP and Raw Pet Food: Why High Pressure Pasteurization Doesn't Belong

There are occasions when we might not have the financial means, time, or desire to prepare homemade raw meals for our carnivore companions. Luckily there are many companies that are in the pet food industry that make complete pre-made raw food. All you do is defrost, portion out and feed. Unfortunately though, while we would like to think all raw food companies are producing quality products, following raw feeding principles and goals, that isn’t always the case. One emerging practice that many raw pet food companies are adopting is High Pressure Pasteurization or HPP. What is High Pressure Pasteurization?

In short, HPP is designed to sterilize a food item by destroying bacteria and preserving raw pet food, supposedly making raw pet food safer and extending its shelf life (1). This is achieved by non thermal or heat based (although low temperatures are used) processes using high pressure. You may be familiar with this concept as we have often heard of pasteurized milk, eggs and juice. We also consume many products that use HPP like salsa, guacamole, jams, jellies and smoothies.

HPP is a process approved by the USDA (2,3). It involves placing the sealed food in a water filled steel chamber where intense pressure is applied to the product through a series of pumps. The food is sterilized and better preserved by inactivating microorganisms and enzymes (4) .

What is considered high pressure?

Glad you asked. It means 50,000 pounds per square inch or more is being applied to a product. Now, let's put that into perspective. Think about deep-sea divers who venture into the ocean's depths with oxygen tanks. As they descend, the water's immense weight poses a risk of oxygen poisoning because of the pressure applied on the oxygen in the tank (5). The Mariana Trench, the deepest of them all, plunges down to a staggering depth of about 11,034 meters (36,201 feet) - that's seven miles below sea level, even deeper than the height of Mount Everest, which stands at 29,032 feet. The pressure in the Mariana Trench measures at a whopping 1,086 bars (the unit used for pressure). How does HPP compare? Well, HPP applies pressure approximately five times greater than that experienced in the Mariana Trench.

What does HPP actually do to the food?

The pressure that is applied breaks the hydrogen bonds (6) in proteins, which not only are found in meat, but make up enzymes, hormones and what is secreted by immune cells. These bonds typically are responsible for the stability and structure of the protein. The structural integrity of proteins plays a crucial role in their ability to perform specific functions. When a protein undergoes conformational changes, it loses its capacity to interact with particular substrates and receptors, resulting in a loss of functionality (7). Properly structured proteins are essential for various fundamental processes, including growth and maintenance, biochemical reactions such as metabolic enzymes (8) that drive your pet's metabolism, energy production (9), blood clotting (10), muscle contractions (11), and more (12).

Proteins also serve as the building blocks for hormones, facilitating cellular communication within your companion's body. Additionally, they contribute to maintaining the body's proper pH balance and play a pivotal role in fluid regulation. These versatile molecules are involved in the creation of immunoglobulins, also known as antibodies, which are vital for combating infections. Furthermore, proteins aid in the transport and storage of nutrients and serve as an energy source. In essence, proteins are the backbone of many essential processes that keep your pet healthy and vibrant. So intact protein is quite essential for the proper functioning of the carnivore body.

Why is HPP a problem?

Now it sounds great that bacteria is being destroyed and that chemical preservatives or additives can be reduced in the final product, at the end of the day you eat food treated with HPP and you're alive to tell the tale, right?

First of all, not all bacteria is bad. There is actually a lot more good and non disease causing

bacteria out there (13). The gut is teeming with good bacteria. It is the good that keeps any bad microorganisms in check. The good bacteria outcompetes the bad by starving them of nutrients and resources, some even specifically target disease causing microorganisms (14). It's not just important for utilizing nutrients properly but it also helps to stimulate the immune system (15), plays a role in brain development (16), generates vitamins and helps to eliminate foreign bodies.

Despite popular belief it is not easy to supplement a diet to stimulate a healthy microbiome, only a truly raw diet that is minimally processed, containing all its natural bacteria can support a healthy gut, microbiome and superior immune system.

However HPP does not discriminate between good and bad bacteria so ALL bacteria that can be destroyed is….good or bad (17).

Unfortunately there are now super bacteria that are surviving these extreme temperatures and environments and unfortunately reproducing to create more bacteria with this same mutation when they replicate (18).

Despite HPP, there is still a risk for recontamination. The food is only preserved and sterilized for as long as the package is closed. Recontamination is actually one of the leading causes for recalls! Most contamination is not due to the product but human error.

Ultimately HPP does not really beat more traditional heat based pasteurization in regards to killing bacteria, microorganisms, spores and viruses. It has yet to be determined if HPP is effective against viruses or mold (19). More times than not spores go into a dormant state during HPP then germinate at a later time causing illness and disease (20). Due to this fact, companies are starting to add heat pasteurization as well as irradiation to their process in the hopes there will be a piece of equipment some day that will provide the ability to kill all bacteria, viruses, molds and anything else left in the food that can be labeled as “bad’. That all being said, heat and the destruction of proteins, vitamins, minerals and heat sensitive fats and enzymes is one major reason we feed a raw diet so a process involving heat makes little sense.

High pressure environments also destroy and alter sensitive ingredients such as enzymes which degrade in the range of 20-60% (21). Fat is also affected.

Enzymes play a crucial role in ensuring the proper functioning of your pet's body. They are a key component in aiding your furry companions in effectively digesting and absorbing the essential nutrients from their food. Without these vital enzymes, many pets experience digestive issues, muscle wasting, weight gain, malnutrition, and absorption problems (13), leading to a range of health concerns (22).

When the body's enzyme reserves are depleted, the pancreas takes on an increased workload to compensate. This heightened activity can lead to a condition known as pancreatitis, characterized by inflammation of the pancreas. Ordinarily, digestive enzymes facilitate the breakdown of food. However, when these enzymes are lacking, the pancreas must release an excessive amount of enzymes, inadvertently causing harm to itself in the process (23).

Fat is also affected and unfortunately to a dangerous level. HPP increases lipid oxidation or the degradation of fats. Free Radicals, molecules with an unpaired electron that are very unstable, take electrons from the cell membrane creating cell damage (24, 25). This typically affects polyunsaturated fats found in meat like fish, beef and lamb. While we live in a society where we see fat as bad and this may seem like a great side effect, polyunsaturated fatty acids are often the first to be affected. They are essential for the function of your companions nerves (26), promoting healthy blood clotting (27), supporting brain well-being (28, 29), and strengthening your muscles (30). Lipid oxidation can also permanently mutate DNA as well as cause cancer (31). Another byproduct of this damage is Reactive aldehyde species or RASP. The molecules are toxic, promote inflammation (32), create autoantibodies which are immune proteins that erroneously identify and react to an individual's own tissues or organs (33) and alter how proteins function (34).

While its claimed minimal depletion is caused by vitamins and minerals it has been found that after HPP Vitamin A is degraded by 20% and Vitamin C by 22-35% (35, 36).

While HPP has been studied on human foods like fruits and vegetables as well as prepared products like yogurt, milk, juices, salsa etc. there are little studies performed directly on pet food.

One study however, performed in 2016, by researchers at Colorado State University conducted a study to assess the effectiveness of HPP in reducing microbial contamination in a beef-based raw dog food. The food was intentionally contaminated with non-pathogenic Escherichia coli test species to simulate the response of pathogenic Salmonella in similar foods. After subjecting the food to HPP and subsequent frozen storage, the results showed a significant reduction in microbial counts, indicating that HPP effectively decreased bacterial levels. However, it did not achieve complete sterilization, which raises concerns for the process's goals (37).

HPP is often labeled as a "natural" preservation method due to its avoidance of chemical additives, it's essential to scrutinize this claim. HPP induces alterations in the product that deviate from the natural state and diet of our beloved animal companions, raising questions about its true "naturalness."

Moreover, it's worth noting that the machinery needed to execute HPP comes with a substantial price tag. As a result, the cost of your raw pet food is likely to surge to offset this significant business expense.

So Why are Companies using HPP?

It's important to note that HPP is not a mandatory procedure for raw pet food companies. However,

due to the FDA's longstanding concerns about the safety of raw pet food, companies face substantial pressure stemming from the FDA's Food Safety Modernization Act of 2011 (FSMA) (38). This act puts a zero tolerance policy on bacteria found in raw pet food. This does not apply to other pet food types like kibble who have had major bacteria contamination outbreaks over the years as well as excessive vitamin content and positive tests for aflatoxins in food. This standard doesn’t even apply to human food which is absurd since salmonella is allowed in chicken you find at the grocery store for people (39)!

Unfortunately though we all know once you have a recall, your company now has a target on its back and that's quite bad for business so fear of these repercussions are persuading raw pet food companies to start using HPP on their products unfortunately praying on the concerns of pet owners versus educating their clients.

Raw food doesn’t need to be safer. Our companions are designed to consume raw meat, organs and bone. Healthy companions have the anatomy and physiology to neutralize bacteria and as long as proper sourcing, handling, storage and disposal are utilized there is little risk to humans. Many raw feeders opt for raw food over kibble or canned alternatives for several reasons. Raw food is valued for its freshness, minimal processing, preservation of natural integrity, absence of denaturation, and retention of essential vitamins, minerals, proteins, fats, and enzymes in their original form. Therefore it is reasonable to conclude the informed raw feeder should not feed raw food treated with HPP.

What Raw Food Companies use HPP? Now we don’t like calling out or bashing companies, but this is an important topic and with the growing popularity of this practice a list is necessary so pet owners and raw feeders have the knowledge to make the best decisions for their carnivore companions.

Keep in mind companies are not required to mention they use HPP. Some will provide this information on their website, others don’t. Prey Model Raw Companies

Texas Tripe

Bravo

Blue Ridge Beef

Steve's Real Food

Raw Dog Food and Company (some of the 80/10/10 blends)

PMR+ Raw Companies

Vital Essentials

We Feed Raw

Steve's Real Food

Non Prey Model Raw Companies

​Primal

Northwest Naturals

Stella and Chewy’s

Nature's Variety Instinct

Steve's Real Food

Tuckers *This list is not all inclusive we will update it as new information presents itself

RESOURCES: Gezai Abera W/giorgis | Fatih Yildiz (Reviewing editor) (2019) Review on high-pressure processing of foods, Cogent Food & Agriculture, 5:1, DOI: 10.1080/23311932.2019.1568725

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