Are macro and micronutrients damaged by intense pressure? High pressure pasteurization (HPP) is a popular pathogen intervention method that has sparked some controversy in recent years due to its potentially damaging effects on cellular integrity. This document seeks to provide clarity in regards to HPP’s effect on macronutrients, micronutrients and microplastic contamination. It will also clarify conditions and variables that would render HPP more or less effective.
The macronutrient composition (protein, fat, fiber, carbohydrates, moisture) of a food product significantly influences the outcomes of the high-pressure pasteurization (HPP) process. Misapplication of HPP not only risks product safety but also undermines the integrity and quality of the final product. (Vocabulary – “Toller” = HPP processor)
HPP is MOST effective on
–High-protein foods – Proteins tend to denature under pressure (HPP), disrupting the cell walls of pathogens and leading to greater inactivation.
–High moisture foods – The moisture content of the food must be >60-80% (depending on the composition of the food) to ensure HPP is effective. High-moisture environments are necessary to uniformly distribute the water pressure, leading to more consistent inactivation of pathogens.
HPP is LEAST effective on
–High-fat foods – Research suggests that fat levels as low as 10% can start to have a protective effect on pathogens during HPP. The protective effect increases as the fat content rises. Fat can encapsulate pathogens or create microenvironments within the food matrix that are less affected by the pressure.
–Low-moisture foods – If the moisture content of the food is <60-80% (depending on the composition of the food) then HPP is ineffective due to lack of uniform pressure.
These facts make it essential to tailor HPP applications to the specific characteristics of the food.
The amount of pressure and time that pressure is applied must be accurate to ensure pathogen mitigation.
Standard HPP pressure and time are generally effective for pathogen reduction but depend heavily on the food’s composition, particularly water activity and fat content. Lower pressures or extended processing times are less effective and can lead to insufficient pathogen inactivation, increasing the risk of recalls and the impact on the product.
In a presentation at the recent annual AAFCO meeting, August 2024, Dr. Grace Danao, Research Associate Professor and specialist on HPP at the University of Nebraska states that some companies request “’instead of using the highest pressure for a short amount of time, we want to use the lowest pressure for a longer period of time.’ That’s not going to work at all. If you use a little pressure, you’re not going to get the infiltration of those proteins from the cellular membranes… plus, the toller will charge you more because now you’re holding their equipment three times longer, and so their throughput is being affected throughout the day as well.” She also states that HPP is “just a pasteurization technique. It’s not for sterilization.” If you want to sterilize the product, you must add an anti-microbial agent to the food.
STANDARD – 600MPa for 3 minutes (87,000 psi)
LOWEST TOLLERS WILL GENERALLY PROCESS – 500MPa for 5 minutes + a surcharge for longer processing times.
LOWEST PRESSURE OPTION TO IRREVERSIBLY DAMAGE MICROBIAL CELLS – 450MPa
LEAST EFFECTIVE AND UP TO 3X MORE EXPENSIVE – 300MPa for 9 minutes will still create “irreversible changes to the proteins…” but will not necessarily inactivate pathogens.
Standard HPP practice for pet food:
PRESSURE –
87,000psi (pounds per square inch)
= 600MPa (megapascals)
= 6,000 bar
“This is equal to the pressure at 6.7-7x the amount of pressure that you would see at the bottom of the Mariana Trench or deepest part of our ocean. I always tell people there’s really nothing natural about these pressures.” Dr. Grace Danao
Safety – But if HPP is done, the product is safe, right? No. Previously, we discussed the importance of ensuring that the product is high moisture and low-fat to ensure efficacy. Freeze-dried, dehydrated, and other low-moisture foods will not benefit from HPP. High-fat foods will not benefit from HPP. What else might negatively affect the effectiveness of HPP? Let’s look at the process:
High-Pressure Pasteurization/Processing on Pet Food:
Potential contamination points are in bold. The time and temperature of the product at steps 7 and 9, nutrient composition, and HPP pressure and time used will determine how effective the high-pressure processing will be.
Step 1 – Receive meat/liquid ingredients
Step 2 – Tempering or frozen meat/organ
Step 3 – Weigh/Batch all ingredients
Step 4 – Grind
Step 5 – Blend/Mix
Step 6 – Package into 10lb tubes for HPP
Step 7 –
Ship to HPP toller. The more time it takes to get to the toller, the less effective HPP is.
Step 8 –
HPP is done at the toller. With the nutrient composition in mind, if the correct pressure and time is applied then HPP will inactivate pathogens.
Step 9 –
Ship from toller to manufacturer for hte final production. Great than 24 hours of transit time can significantly increase the risk of recovery of listeria.
Step 10 –
Grind. The food is removed from the packaging done in step 6, potentially recontaminating it.
Step 11 – Form into sliders, patties, nuggets etc.
Step 12 – Patial Freeze.
Step 13 – Transfer into final packaging.
Step 14 –
Final freeze. This may help precent pathogen growth. Freezing cannot kill pathogens that have contaminated the product during any of the BOLDED steps or recovered after step 8.
Nutrient composition before and after HPP –
HPP does alter the composition of food. When 3 raw eggs were HPP’ed, this was the result.
For more information click HERE and visit www.thyssenkrupp-hpp.com
Some manufacturers claim that there is an increase in nutrients after HPP – implying that HPP magically creates vitamins and minerals out of nowhere. Is this possible? No. Let’s look at what’s happening.
*Moisture content – pre and post HPP
Water loss is why nutrients falsely appear to increase after water loss caused by HPP
*Food chemistry analysis has several inherent limitations that can lead to discrepancies in nutrient calculations. Laboratories use different methods to measure each component (protein, fat, fiber, moisture, etc.), and these methods can have slight inaccuracies or variations, especially when handling complex food matrices. For instance:
1. Laboratory Moisture Overestimation: Moisture is often difficult to measure precisely, especially when high, leading to inflated numbers that skew totals.
2. Sampling Variability: Even slight differences in sample composition (like fat or fiber distribution) can affect results. High Pressure Pasteurization (HPP) or other processing techniques can also alter moisture and other components in ways that aren’t uniform across all samples.
3. Laboratory Rounding Errors: When summing percentages, small rounding differences can accumulate, pushing totals above 100%.
These issues explain why laboratory-reported values sometimes exceed 100%, as seen in your analysis, and why dry matter can calculate to over 100%, as individual components may have slight over- or under-estimations.
Solutions Pet Products does not want to misrepresent the number provided by the laboratory. Therefore they have been shared exactly as they are listed on the laboratory report.
When a food product undergoes HPP, the cellular matrix is damaged, causing it to lose water and reducing the moisture content. This moisture loss also represents a reduction in the total product weight, meaning the other nutrients become more concentrated not because their amounts have increased, but because they now make up a larger proportion of the smaller, more concentrated product.
Water is one of the most beneficial components in raw pet foods. In addition to its contributions to whole-body health, water contributes to the body’s ability to transfer nutrients from place to place. The significant moisture loss in Sample #1 compared to Sample #2 suggests that HPP may cause greater water loss in products with higher moisture content. This loss can potentially reduce nutrient availability and bioavailability. While the high moisture content in Sample #1 enables effective pathogen inactivation at standard HPP settings (600 MPa for 3 minutes), it also makes high-protein foods more vulnerable to protein denaturation, diminishing their nutritional value and digestibility. Additionally, pathogens like Listeria monocytogenes can recover during storage if HPP is not paired with antimicrobial treatments or rigorous refrigeration. It is impossible to compare the nutrient content of two reports with different moisture levels unless you convert the nutrients to Dry Matter (DM).
PROTEIN CONTENT CONSISTENTLY DECREASES AFTER HPP TREATMENT
Sample #1 (higher protein) – 14.99% protein loss after HPP
Sample #1 – pre-HPP – 66.2% DM, post-HPP – 51.21% DM
Sample #2 (higher fat) – 0.74% protein loss after HPP
Sample #2 – pre-HPP – 37.08% DM, post-HPP – 36.34% DM
HPP processing can significantly alter protein structure, leading to denaturation, which disrupts the protein’s native form and affects its functional properties. This denaturation can reduce protein solubility, causing proteins to form aggregates that are harder to detect and quantify using standard analytical methods, resulting in a lower measured protein content in the HPP sample. The marked decrease in protein in Sample #1, compared to the lesser change in Sample #2, suggests that HPP has a more pronounced impact on high-protein foods, where denaturation and aggregation are more significant, leading to a greater reduction in measurable protein content. This highlights the need for careful consideration of initial protein levels when applying HPP, as higher protein concentrations may be more susceptible to damage during the process.
The International Association of Food Protection (IAFP) provides laboratory analyses suggesting that HPP can significantly alter the protein content in pet food, potentially decreasing the bioavailability and nutritional value of essential amino acids. Proteins are composed of amino acids, which are necessary for numerous biological functions in animals. When subjected to HPP, the structure of these proteins can be disrupted, leading to potential denaturation. This process does not create new amino acids but can release existing ones from their protein structures, altering their availability and functionality.
The wet matter analysis of the pre and post-HPP samples initially suggests an increase in amino acids such as tryptophan and histidine. However, when these results were compared on a dry matter basis—removing the influence of water content lost in the HPP process—it became clear that there was no actual increase in these nutrients. This discrepancy underscores the potential for wet matter analysis to falsely imply increased nutrient density in post-HPP samples, which is misleading.
More critically, dry matter analysis revealed a decrease in essential amino acids such as cystine, methionine, and alanine, despite wet matter results falsely implying an increase. This indicates that HPP may cause degradation or structural changes in proteins, leading to a reduction in these crucial amino acids. Such changes could negatively impact the nutritional value of the food, as these amino acids play vital roles in health and must be absorbed efficiently for optimal benefits.
Additionally, the analysis showed an increase in amino acids such as arginine, aspartic acid, and glutamic acid, among others, in both wet and dry matter comparisons. This suggests that these amino acids may be more resistant to degradation under HPP or that they are being released from more complex protein structures due to the processing. While these increases might initially seem beneficial, they could actually indicate that the original protein structures were damaged, potentially reducing the overall quality and absorbability of the proteins.
INCONSISTENT IMPACT ON FAT
Sample #2 (higher fat than #1) – 2.26% fat increase after HPP
HPP can induce oxidative reactions in fats, leading to degradation and the formation of volatile compounds that may compromise the accuracy of fat measurements. The contrasting changes observed between samples illustrate HPP’s inconsistent effects, which are heavily influenced by initial fat content, moisture levels, and fat types, making it imperative that manufacturers assess the appropriateness of HPP on each recipe prior to implementation. Additionally, the protective nature of fats and low water activity can reduce HPP’s effectiveness in inactivating pathogens like Listeria monocytogenes, often requiring higher pressures, longer processing times, or supplementary antimicrobials, which can significantly increase production costs.
These observations underscore the critical importance for HPP scientists to clearly communicate the necessity of understanding and accounting for macronutrient ratios in food products. Tailoring HPP applications based on specific nutrient compositions is essential to ensure accurate nutrient measurements, effective pathogen control, and optimal product quality. Failure to do so can increase the risk of product recalls and degrade performance. It is crucial that scientists ensure manufacturers do not apply HPP to unsuitable foods like freeze-dried, dehydrated, kibble, high-fat, or low-moisture products, and that they are aware of which nutrients may be compromised, enabling appropriate compensatory measures.
Further research is essential to fully validate these observations and to develop processing techniques that preserve the nutritional value of pet food while ensuring safety.
INCONSISTENT IMPACT ON FIBER
Sample #1 (high fiber) – 3.36% fiber loss after
Sample #1 – pre-HPP – 18.22% DM, post-HPP – 14.86% DM
Sample #2 (low fiber) – 0.7% fiber increase after HPP
Sample #2 – pre-HPP – 4.81% DM, post-HPP – 4.88% DM
HPP can alter the solubility of dietary fibers, especially in high-fiber foods, leading to the potential loss of water-soluble fibers and resulting in lower measured fiber content. The significant reduction in fiber in Sample #1, compared to the lesser change in Sample #2, indicates that HPP may have a more substantial impact on foods with higher initial fiber content. This underscores the importance of understanding how macronutrient ratios influence HPP’s effects. HPP scientists must clearly communicate these potential impacts to manufacturers, ensuring they recognize which nutrients might be compromised and how to compensate for these changes. Failure to do so risks degrading product quality and increasing the likelihood of recalls.
EFFECT ON VITAMINS AND MINERALS
IAFP and other pre and post-HPP sample analyses also assess the impact of HPP on vitamins and minerals.
Sample #1 – higher protein, significantly higher fiber, and slightly higher moisture than sample #2
Sample #2 – higher fat than sample #1
Calcium, Phosphorus, and Mineral Analysis
Wet matter analysis suggested increases in calcium levels post-HPP in both samples #1 and #2. However, dry matter analysis, which provides a more accurate assessment by removing water content, revealed a decrease in calcium content, with losses ranging from 0.08% to 0.13%. Similarly, phosphorus showed an implied increase or no change in wet matter analysis but a decrease of 0.09% to 0.13% in dry matter analysis across both samples. This pattern was consistent for other minerals, including zinc, magnesium, potassium, sodium, copper, and iron, where wet matter results implied increases, but dry matter analysis revealed decreases. This suggests that HPP may damage the mineral content or alter its availability, potentially through changes in the food’s cellular matrix that affect nutrient stability.
Vitamin and Fatty Acid Analysis – Vitamins and fatty acids also showed discrepancies between wet and dry matter analyses. For instance, Vitamin A and Vitamin K showed implied increases or no changes in wet matter analysis but were found to decrease by 1380.72 IU/kg and 0.007%, respectively, in dry matter analysis. Fatty acids, such as linoleic acid and omega-6, exhibited the most significant increases in wet matter analysis, yet these results could indicate damage to the fat matrix, making the fats more susceptible to oxidation and less bioavailable.
Enzyme Activity and Nutrient Metabolism – HPP’s impact on the food’s cellular matrix may also extend to enzyme activity, which plays a crucial role in converting precursor compounds into active forms of nutrients. For example, if HPP alters the enzymes involved in niacin conversion or synthesis, this could lead to misleadingly higher levels of niacin in the HPP-treated samples. However, this alteration could negatively impact the body’s ability to metabolize these vitamins effectively once consumed, potentially leading to deficiencies in the active forms of vitamins or hindering their conversion into forms that can be utilized by the body. Such changes underline the importance of considering the effects of HPP on both nutrient content and enzyme functionality.
Laboratory Variability and Standard Deviation – It is important to recognize the inherent variability in laboratory analysis. Nutrient deviations observed between pre- and post-HPP samples might partially be attributed to standard deviations in laboratory measurements or sample homogenization issues. For instance, copper has a known standard deviation of about 25%, which can result in inconsistent test results. Additionally, the sensitivity of laboratory instruments might lead to higher readings post-HPP due to the breakdown of cellular structures that make nutrients more detectable. This variability emphasizes the need for cautious interpretation of laboratory results and highlights the complexity of accurately assessing the impact of HPP on pet food nutrition.
SO IS A HIGH-PRESSURE PASTEURIZED PRODUCT REALLY RAW?
It depends on your definition of “raw.” ” The definition of “raw” food traditionally refers to food that has not been cooked or significantly processed, thus preserving its natural enzymes, vitamins, and nutrients. High-pressure pasteurization (HPP), though non-thermal, applies extreme pressure that can alter the food’s cellular structure, enzymes, and nutrients. Therefore, HPP-treated meat does not fully qualify as raw by this standard definition.
Several lawsuits in the human food industry have challenged the labeling of HPP-treated products as “raw.” Notably, Suja Life, LLC, Hain Celestial’s BluePrint juices, and Forager Project were sued for misleading consumers by labeling HPP-treated juices as “raw.” The FDA has clarified that HPP-treated juice cannot be labeled as “fresh” under 21 CFR 101.95. Companies like Starbucks label their juices as high-pressure pasteurized to avoid legal issues. Despite these facts, HPP tollers like Avure Technologies continue to claim that key nutrients remain intact.
DAMAGED CELLULAR INTEGRITY:
A healthy cell has intact and functional membranes, imperative for selective permeability and effective communication. This description typically pertains to cells within the body but cells from raw food also have nutrients encapsulated within compartments, aiding gradual release and absorption during digestion. These intact cells interact optimally with the digestive tract, enhancing nutrient uptake. Raw food also contains bioactive compounds like enzymes and polyphenols that are required for cellular signaling and antioxidant defense. Preserving cellular integrity in food allows these compounds to remain active and support cellular function.
Companies rarely convert laboratory comparisons to reflect dry matter, which overlooks the fact that HPP consistently leads to a reduction in moisture content. This decrease is a direct result of cell damage, which compromises cellular membranes’ integrity and permeability. As a consequence, cells lose their ability to regulate ion gradients.
Scientific data shows that HPP fragments the cellular structure, making it “leaky” (like an exploded building vs a complete, finished building). Data determining the effects of exclusively consuming, as a complete diet, destroyed cells is incomplete. Nature does not provide large quantities of ruptured cells except in, perhaps, very rotten corpses. In rotting tissue, science shows that histamine and inflammatory compound levels are increased, sometimes dramatically.
Cell 1 Cell 2
Cell 1 – PRE HPP CELL Cell 2 – POST HPP CELL (600MPa)
Should you worry about plastic in HPP products?
There is limited data on the effects of phthalates and plasticizers in post-HPP (high-pressure pasteurization) samples, but several concerns are worth noting. HPP uses extreme pressure, over six times greater than the deepest part of the ocean, which requires flexible plastic casings with high levels of phthalates and plasticizers. These chemicals can detach from the plastic and migrate into food when heat, cold, or pressure are applied. Steve’s Real Food (SRF) referenced research states, “…significant migration of compounds from the plastic material was observed, but it was not enhanced by the high-pressure treatment (400 MPa, 10 min, 12*C).” This doesn’t eliminate the risk of plastic exposure. Phthalates such as DEHP, DINP, DIDP, DBP, and BBP, used in plastics for HPP processing, are known endocrine disruptors linked to reproductive toxicity, hormone disruption, and other health issues. Even small daily exposures can accumulate in the body over time, leading to significant health risks, including hormone imbalances, mineral disruptions, and increased heavy metal toxicity.
Phthalates like DEHP and DINP have been shown to disrupt thyroid and adrenal functions, leading to potential thyroid dysfunction, impaired stress responses, and cardiovascular issues. BBP and DBP can interfere with hormone regulation, potentially leading to conditions similar to menopause in both males and females. Given these risks, it’s advisable to ask manufacturers of HPP foods for post-HPP phthalate and plasticizer test results with a detection limit of 1-10 ppb. Testing with a limit of detection (LOD) above 1 ppm may not provide an accurate assessment of safety. Further, it is important to consider that exposure is cumulative. “Too much” phthalate/plasticizer is >1ppm. If only 50ppb/day is consumed, in only 20 days >1ppm would have been consumed. The body does not have a mechanism for detoxifying microplastics.
Ultimately, the use of HPP-treated foods as a sole source of nutrition could lead to long-term health issues due to the potential accumulation of endocrine-disrupting chemicals.
References:
- IAFP Presentation – Dr. S. Tejayadi, Dr. B. Johnson, Dr. M. Sayles, Dr. J. Kersey, Dr. J. Acuff
- AAFCO 2024 Meeting Presentation – Grace Danao – Research Associate Professor – consulting and testing services (mostly HPP, food safety, engineering, temperature mapping, and near infrared spectroscopy/chemometrics). Co-staff include Prashant Dahal, Research Technologist (HPP, high pressure homogenization, freeze drying), and Yhuliana Nino Guere, M.S. student, and other students’ applied research products (HPP efficacy on inactivation and recover of Listeria spp. And new HPP applications (thawing, enhanced proteolysis, valorization of protein byproducts
- Silva, M. J., et al. (2004). “Urinary levels of seven phthalate metabolites in the U.S. population from the National Health and Nutrition Examination Survey (NHANES) 1999-2000.” Environmental Health Perspectives, 112(3), 331-338.
- Rudel, R. A., et al. (2011). “Phthalates, Alkylphenols, Pesticides, Polybrominated Diphenyl Ethers, and Other Endocrine-Disrupting Compounds in Indoor Air and Dust.” Environmental Science & Technology, 45(17), 6965–6972.
- EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF). (2019). “Risks to human health related to the presence of di-(2-ethylhexyl) phthalate (DEHP) in foodstuffs: Scientific opinion of the Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF).” EFSA Journal, 17(7), e05732.
- EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). (2019). “Risks to human health related to the presence of diisononylphthalate (DINP) and diisodecylphthalate (DIDP) in foodstuffs: Scientific opinion of the Panel on Food Additives and Nutrient Sources added to Food (ANS).” EFSA Journal, 17(4), e05650.
- Rodricks, J. V., et al. (2010). “Evaluation of the hazards of industrial chemicals: Diisononyl phthalate.” Journal of Applied Toxicology, 30(4), 291-302.
- Puupponen-Pimiä, R., et al. (2001). “Effects of High-Pressure Processing on Antioxidants and Anthocyanins in Lingonberry Juice.” Journal of Food Science, 66(1), 116-120.
- Plaza, L., et al. (2004). “High-Pressure Processing of Tomato Puree: Lycopene Stability and in Vitro Bioaccessibility.” Journal of Agricultural and Food Chemistry, 52(25), 7872-7877.
- Leistner, L. (2000). “Basic aspects of food preservation by hurdle technology.” International Journal of Food Microbiology, 55(1-3), 181-186.
- Raikos, V., et al. (2011). “Effect of High-Pressure Processing on the Rheological and Microstructural Properties of Tomato Puree.” Food and Bioprocess Technology, 4(5), 819-826.
- Tapia, M. S., et al. (2008). “Impact of high-pressure processing on vitamin C, vitamin E, flavonoids, and antioxidant activity of fruit beverages.” Innovative Food Science & Emerging Technologies, 9(1), 117-122
- Zagger, Zachary (2013) “Specialty Food Co. Accused of Selling Bogus ‘Raw’ Juice.” Law360.com
- High Pressure Food Processing (HPP). Kobelco.co.jp