High-Pressure Processing Tames Dangerous Bacteria in Raw Beef Pet Food

Raw pet food has become one of the fastest-growing segments of the companion animal market, driven by owners who increasingly regard their dogs and cats as family members and who want diets that look more natural and less processed than extruded kibble. But the same minimal processing that makes raw diets appealing also leaves them vulnerable. Because raw meat products are distributed without a terminal heat treatment, they can carry zoonotic pathogens such as Salmonella, Listeria, and pathogenic Escherichia coli, posing risks not only to pets but also to the humans who handle their food. A new study published in Food Science of Animal Resources by Ui-Bin Baek and Hack-Youn Kim of Kongju National University in South Korea now offers a detailed map of how high-pressure processing, a non-thermal sterilization technology, can make raw beef safer while revealing the quality trade-offs that come with it.

The research team set out to answer a question that has practical consequences for the pet food industry: how much pressure is enough to kill dangerous microbes, and how much is too much before the meat itself begins to suffer? They treated raw beef loin, a primary ingredient in raw pet food formulations, at pressures of 0.1, 100, 300, and 500 megapascals for holding times of 5 to 15 minutes, then tracked both microbial survival and a battery of physicochemical properties over two weeks of refrigerated storage. Five pathogens were inoculated onto the meat: Salmonella Typhimurium, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus. The samples were vacuum-packed and processed within two hours of inoculation to minimize any changes in microbial populations before treatment.

The microbial results followed a clear pressure-time hierarchy. At 100 megapascals, the inactivation effect was limited, consistent with reversible cellular responses rather than irreversible damage; membranes may become permeabilized without sufficient disruption of intracellular structures, allowing microorganisms to recover. As pressure increased, structural disruption of cell membranes and protein denaturation progressed, leading to irreversible cellular damage. The most striking result came at 500 megapascals for 15 minutes, where Salmonella Typhimurium was reduced to below the detection limit of one log colony-forming unit per gram and was never re-detected during the entire two-week storage period. The other pathogens were not completely eliminated, but they showed substantial reductions with limited regrowth.

The differential survival of the pathogens tells a fascinating story about cell architecture. Gram-positive bacteria such as Listeria monocytogenes and Staphylococcus aureus possess thicker peptidoglycan layers than their gram-negative counterparts, conferring greater pressure resistance. Among all the organisms tested, Staphylococcus aureus proved the toughest, and the authors attribute this to a suite of defensive features: the antioxidant pigment staphyloxanthin, a high content of branched-chain fatty acids in the cell membrane, extensive secondary cross-linking of peptidoglycan, and teichoic acids that stabilize the cell wall against deformation. Immediately after the 500-megapascal, 15-minute treatment, E. coli, Listeria, Staphylococcus, and Bacillus were reduced by 77.47, 77.58, 48.77, and 71.83 percent respectively compared with the control, and over the storage period the reductions reached 59.46, 68.35, 53.39, and 92.08 percent.

Bacillus cereus added another layer of complexity because of its spore-forming ability. Rather than being killed directly, pressures above 50 megapascals stimulate germinant receptors and SpoVA channels within the spores, triggering the release of calcium and calcium-dipicolinic acid and raising the water content of the spore core. Once germinated, the spores convert into vegetative cells, losing their pressure resistance and becoming more susceptible to oxidative stress and DNA damage. This supports what the authors describe as a germination-inactivation sequence rather than direct spore lethality, a nuance that matters greatly for shelf-stable product design.

On the quality side, the picture was more mixed. Proximate composition, meaning moisture, protein, fat, and ash content, remained unchanged across all treatments, largely because vacuum packaging prevented drip loss, the main route by which pressure treatment can alter bulk nutritional composition. pH was similarly stable throughout processing and storage, which the researchers link to the suppression of microbial metabolism and endogenous enzymatic activity, the two main drivers of postmortem biochemical change. However, higher pressures and longer holding times increased lightness, yellowness, shear force, water-holding capacity, and thiobarbituric acid reactive substances, a marker of lipid oxidation, while redness declined. The 500-megapascal, 15-minute treatment raised lightness by 36.95 percent compared with the control, producing a visibly paler product.

One of the most intriguing findings is a paradox in texture. The highest pressure-time combination produced both the greatest water-holding capacity and the highest shear force, meaning the meat held more water yet became tougher. The authors explain this through pressure-induced protein aggregation: dissociated myofibrillar proteins interact through exposed sulfhydryl groups and hydrophobic residues, forming gel-like networks that immobilize water within a mechanically rigid matrix. Water retention, in other words, does not equal tenderness under high pressure. Meanwhile, color changes were governed by non-linear interactions between structural light scattering and myoglobin redox chemistry; at an intermediate 300 megapascals, metmyoglobin-reducing enzymes remain active enough to partially preserve redness, whereas 500 megapascals inactivates those enzymatic defenses.

Oxidation and spoilage chemistry also responded to pressure in opposing directions. Lipid oxidation, measured as TBARS, increased with both pressure intensity and storage time, driven by the release of non-heme iron when myoglobin’s porphyrin structure is destroyed; that iron reacts with hydrogen peroxide to generate hydroxyl radicals that attack lipids. Volatile basic nitrogen, an indicator of protein deterioration, moved the opposite way, falling significantly at 500 megapascals because high pressure suppresses both the microbes and the proteolytic enzymes, including calpains and cathepsins, that would otherwise degrade muscle proteins. Yet even here, storage mattered: VBN values climbed in all groups by week two, suggesting residual enzymatic activity persists after treatment.

The study’s practical conclusion is that processing intensity must be optimized rather than maximized. The 500-megapascal, 15-minute condition delivered the strongest antimicrobial effect but also the worst quality outcomes, including tougher texture, more lipid oxidation, and color deterioration. Moderate conditions around 300 megapascals for 15 minutes achieved substantial microbial reduction while better preserving the attributes that determine palatability, which matters because companion animals are sensitive to texture and appearance as well as to microbial hazards. The authors acknowledge limitations, notably the absence of sensory evaluation, and propose that future work employ electronic nose and tongue instruments and gas chromatography-based volatile analysis, along with digestibility trials, to establish biologically relevant processing windows. For an industry racing to make raw diets safe without making them sterile and unappetizing, this study provides exactly the kind of pressure-time framework needed to find that balance.

Subject of Research: Effects of high-pressure processing on microbial safety and physicochemical quality of raw beef loin for pet food

Article Title: Analyses of the microbial safety and physicochemical characteristics of beef loin treated with high-pressure

Article References: Baek, U.-B., & Kim, H.-Y. (2026). Analyses of the microbial safety and physicochemical characteristics of beef loin treated with high-pressure. Food Science of Animal Resources, 46(1), Article 74. https://doi.org/10.1007/s44463-026-00081-w

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00081-w

Keywords: high-pressure processing, raw pet food, beef loin, foodborne pathogens, Salmonella, Listeria monocytogenes, Staphylococcus aureus, microbial inactivation, lipid oxidation, meat quality, non-thermal sterilization, food safety