Dog food recalls are far too common, often due to contamination with bacteria like Salmonella. The Food Safety Modernization Act (FSMA) mandates "zero tolerance" for Salmonella in raw pet food, prompting manufacturers to seek ways to avoid bacterial contamination. Many choose High-Pressure Pasteurization (HPP), which is claimed to be ideal because it retains nutrients while eliminating bacteria. However, HPP also destroys beneficial bacteria and digestive enzymes, resulting in a product with minimal living organisms or natural enzymes.

HPP is widely used in the food industry because it maintains quality, extends shelf life, and ensures food safety without high temperatures. In the raw pet food industry, HPP effectively inactivates pathogens such as Salmonella, Escherichia coli, and Listeria monocytogenes, often implicated in food recalls.

HPP is a food preservation method that uses extremely high pressure (100 to 1000 megapascals) to inactivate harmful microorganisms and enzymes. Unlike traditional thermal processing, HPP achieves microbial inactivation without high temperatures, preserving the food's nutritional qualities.

During HPP, pre-packaged food products are placed into a pressure vessel filled with water, which acts as a pressure-transmitting medium. The vessel is then subjected to high pressure uniformly, effectively inactivating bacteria, viruses, yeasts, molds, and other pathogens by disrupting their cellular structures and biochemical processes. Because HPP operates at room temperature or lower, maintaining the food's fresh taste, texture, and nutritional value. HPP is a versatile and environmentally friendly alternative to conventional kibble extrusion techniques.

Studies show that HPP-treated foods retain more vitamins and antioxidants than foods treated with traditional heat processing methods. HPP also better retains nutritional attributes such as flavor, color, and nutrients than thermal processing.

Specific nutrients retained with HPP include Vitamin C, carotenoids, and polyphenols. Research indicates that HPP-treated fruits and vegetables maintain higher levels of vitamin C during storage compared to thermally processed ones. The stability of ascorbic acid under HPP is due to lower degradation rates than thermal methods.

HPP generally maintains the stability of bioactive compounds, though the impact can vary depending on the food type and HPP conditions. In some cases, HPP can enhance the bioavailability of certain nutrients, making them more accessible for absorption. 

While HPP offers significant safety and shelf life benefits, it poses challenges regarding the nutritional and sensory qualities of raw meat-based diets (RMBDs) for dogs. Balancing these aspects is crucial for maintaining RMBDs' benefits while ensuring safety.

One notable effect of HPP on fresh dog food is its impact on protein structure. HPP can change the texture and functionality of meat proteins, affecting how the food feels and behaves. Additionally, HPP can lead to protein oxidation, potentially creating free radicals that initiate various oxidation reactions. These reactions can cause off-flavors in the food and reduce nutritional value by degrading essential amino acids and lowering protein digestibility.

HPP influences enzyme activity in muscle meats, inactivating enzymes such as proteases naturally occurring in raw meat. These enzymes play a crucial role in nutrient digestion and absorption, and their inactivation can reduce the digestibility and nutritional benefits of the meat for dogs.

HPP can also lead to lipid oxidation, affecting the flavor and nutritional quality of the meat. Lipid oxidation can cause rancidity, leading to an off-flavor that may be unappealing to dogs and reducing the overall palatability of the diet. It also results in the loss of essential fatty acids necessary for dogs' health.

Another concern is HPP's effect on the microbiota of fresh diets. While HPP effectively reduces harmful bacteria, it can also affect beneficial microorganisms. For instance, HPP can reduce or eliminate certain probiotics and other beneficial bacteria that contribute to a healthy gut microbiome in dogs, potentially impacting overall gut health.

Other Sterilization Methods for Commercial Fresh Food

Besides HPP, several sterilization steps are used for commercial raw dog food, including irradiation, thermal processing, freeze-drying, fermentation, or chemical preservatives. 

Irradiation employs ionizing radiation, such as gamma rays, X-rays, or electron beams, to eliminate bacteria, viruses, and parasites in food. This process works by breaking down the DNA of these microorganisms, preventing them from replicating and causing illness. Radiation can achieve these effects without significantly affecting the food's nutritional quality, taste, or appearance. The process is highly controlled and regulated to ensure safety and effectiveness, making it a reliable method for decontaminating raw dog food.

Thermal processing involves using heat to kill pathogens in food. Methods include:

Baking: Cooking food at high temperatures in an oven.

These methods effectively kill bacteria, viruses, and parasites by denaturing their proteins and disrupting cellular structures. However, thermal processing can alter the nutritional value and texture of the food. For example, vitamins sensitive to heat may degrade, and the texture of the food may become softer or more solid, depending on the method used.

Freeze-drying, also known as lyophilization, involves freezing the food and reducing the surrounding pressure to allow the frozen water in the food to sublimate directly from the solid to the gas phase. This process removes moisture, which inhibits microbial growth since bacteria, viruses, and parasites need water to survive. Freeze-drying preserves the food's nutritional content, flavor, and texture better than other dehydration methods. It extends the shelf life of raw dog food without refrigeration.

Fermentation involves using beneficial bacteria to convert carbohydrates in the food into organic acids, gases, or alcohol. This process creates an environment that is hostile to harmful pathogens, thus inhibiting their growth. The beneficial bacteria outcompete the harmful ones for resources and produce compounds that further suppress pathogen development. Fermentation not only makes the food safer but also enhances its probiotic content, which can be beneficial for the gut health of dogs.

Chemical preservatives such as organic acids (e.g., lactic acid, citric acid) are added to raw dog food to inhibit microbial growth. These substances work by lowering the pH of the food, creating an acidic environment that is unfavorable for the survival and growth of pathogens. By disrupting the microbial cell membrane and interfering with enzyme function, these preservatives help kill pathogens and prolong the shelf life of the food.

Natural antimicrobial agents include essential oils, vinegar, and plant extracts. These substances have inherent antimicrobial properties that can reduce the pathogen load in raw dog food. Essential oils, such as those derived from thyme, oregano, and rosemary, contain compounds that can disrupt microbial cell membranes and inhibit enzyme activity. Vinegar, which contains acetic acid, lowers the pH of the food, making it difficult for pathogens to thrive. Plant extracts, such as those from garlic and onion, also have antimicrobial effects and can be used to enhance food safety.

These methods are often combined to ensure the safety and quality of commercial raw dog food. For instance, a product might be freeze-dried and then treated with natural antimicrobial agents or chemical preservatives to provide multiple layers of protection against pathogens. By using a combination of these processes, manufacturers can effectively reduce the risk of contamination while maintaining the nutritional integrity and palatability of the food.

When choosing a commercial fresh food diet for your dog, either raw or gently cooked, a key factor is how the food is prepared and what measures are taken to ensure its safety. Companies should be transparent in their manufacturing methods. While HPP offers significant safety and shelf life benefits, it also poses challenges regarding the nutritional and sensory qualities of raw meat-based diets for dogs. Balancing these aspects is crucial for maintaining the benefits of RMBDs while ensuring their safety.

HPP effectively eliminates harmful bacteria in raw pet food while preserving nutrients, but it also destroys beneficial bacteria and digestive enzymes, potentially reducing the food's overall nutritional value.

HPP-treated foods retain more vitamins and antioxidants than foods processed using traditional heat methods, maintaining better flavor, color, and nutritional profiles.

There are several options for sterilization of commercial fresh, other than HPP. 

A Diffusion Model to Quantify Membrane Repair Process in Listeria monocytogenes Exposed to High Pressure Processing Based on Fluorescence Microscopy Data 

Heat assisted HPP for the inactivation of bacteria, moulds and yeasts spores in foods: Log reductions and mathematical models - ScienceDirect 

Comparison of the Effect of Holder Pasteurization and High-Pressure Processing on Human Milk Bacterial Load and Bioactive Factors Preservation - PMC 

Differential gene expression of Listeria monocytogenes during high hydrostatic pressure processing     

Pasteurization of Food and Beverages by High Pressure Processing (HPP) at Room Temperature: Inactivation of Staphylococcus aureus, Escherichia coli, Listeria monocytogenes, Salmonella, and Other Microbial Pathogens | Semantic Scholar   

High pressure processing to control Salmonella in raw pet food without compromising the freshness appearance: The impact of acidulation and frozen storage - ScienceDirect.   

Impact of High-Pressure Processing on Food Quality | SpringerLink  

Impact of High Pressure Processing on the Safety and Quality of Food Products: A Review 

High-pressure processing--effects on microbial food safety and food quality.  

Opportunities and challenges in high pressure processing of foods  

Recent Advances in the Use of High Pressure as an Effective Processing Technique in the Food Industry | Food and Bioprocess Technology  

Effects of high pressure on meat: A review  

High Pressure Processing of Meat, Meat Products and Seafood 

Protein and lipid oxidation in meat: A review with emphasis on high-pressure treatments - ScienceDirect  

The effects of raw-meat diets on the gastrointestinal microbiota of the cat and dog: a review  

One notable effect of HPP on fresh dog food is its impact on protein structure. HPP can change the texture and functionality of meat proteins, affecting how the food feels and behaves. Additionally, HPP can lead to protein oxidation, potentially creating <a href="https://www.feedreal.com/articles/free-radicals-and-natural-antioxidants">free radicals</a> that initiate various oxidation reactions. These reactions can cause off-flavors in the food and reduce nutritional value by degrading essential amino acids and lowering protein digestibility.

Understanding the Effects of High-Pressure Pasteurization on Raw Dog Food

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