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Scientific Evidence of Effects of HPP on Meat Products

by Chelsea Kent

High Pressure Pasteurization (HPP) claims to decrease the potential of pathogens such as Salmonella, Listeria, Campylobacter and E.Coli in raw meat pet food products while still maintaining the “raw” integrity.
How does HPP work? HPP is a non-thermal, cold processing technique in which the food, in its flexible, plastic, oxygen rich packaging, is subjected to high levels of hydrostatic (water) pressure. In 2012, documents were published stating that pressure greater than 400 MPa is necessary to achieve efficient microbial inactivation. However, Staphylococcus Aureus, Spores, Protease Cathepsin, etc are resistant even above 600MPa (87,000 psi (pounds per square inch)). HPP treatment at subzero temperatures (on frozen raw foods) is not effective in decreasing microbial counts in meats due to lack of plasticity of the product. (1)
How much real life pressure is 87,000psi?
When a Scuba Diver is exposed to underwater pressure Boyle’s Law states that effects of pressure cause an increase in the absorption of nitrogen which can lead to oxygen toxicity, nitrogen narcosis, carbon monoxide toxicity and decompression sickness. (19) These physiological effects are usually reversible in a living being because a living being is capable of persistently working to metabolize excess nitrogen and strive for homeostasis, while dead tissue is not. Of course, humans can’t survive the depths of the ocean (17,000 psi) without a submarine. Even a submarine would not survive 30,000psi which bends steel. A Scuba Diver would have to reach 200,685 ft (6.3 times the depth of the Mariana Trench) to reach 87,000psi (21) thus it would take a diver 418 hours of active metabolizing to recover from the physiologic changes caused by the pressure. The tissues of deep water sea-life brought up to shallow surfaces suffer the congealing pressure off its lipids, start to ooze internally and lose integrity in their nerve cell membranes (which get “quite leaky”). (23) Imagine the effects of an animal brought up from 6.3 times that depth!!! Yet that’s what HPP does to your pets’ food.

Mandating (or lack thereof) of HPP
Rumor falsely states the FDA will soon mandate HPP.  This is a false statement.  Since 2009 the FDA has worked with the FSIS (Food Safety & Inspection Service) and FIC (Food Industry Counsel) to enforce HACCP plans (Hazardous Analysis Critical Control Point) to pet food companies (canned food excluded) because the FDA does not have the authority to enforce pathogen stop-gap measures. The 2016 USDA’s FSIS HACCP enforcement program is designed to ensure food safety and quality control by requiring raw and cooked, human and pet food companies to maintain a detailed log of manufacturing processes, standards and tracking. It does not specify or enforce stop gap methods such as HPP, irradiation or cooking. Legally, according to the FSIS authority HACCP, itself, is considered a “stop gap method” just as irradiation, HPP, cooking and “other methods” that are “not yet researched” such as fermentation are (if it can be proven by the company to work) (Answers Pet Food proved to the FDA in a court of law that fermentation is an effective stop gap method).
Damage done by HPP… what does the science say?
HPP fractionates the protein molecule and delays rigor mortis, which is useful for tenderizing. It disassociates myosin, actin, albumin, myoglobin and causes coagulation, aggregation or gelation of sarcoplasmic proteins and myofibrils. (1)(12) Muscle proteins are also susceptible to oxidative reactions that involve the loss of essential amino acids and decrease protein digestibility, thus affecting the nutritional value of the meat. (1) HPP can affect protein conformation and lead to protein denaturation, aggregation or gelation. (10) The higher the fat or water content the greater the “whitening effect” caused by protein coagulation (loss of solubility of sarcoplasmic and myofibrillar protein and/or globin deterioration from heme group displacement). Therefore, in addition to beef and other fatty meats (20-25%) being more susceptible to whitening, they are also more susceptible to lipid oxidations. (1) HPP induces meat protein modifications that result in varying effects on meat product texture and water retention. Because of this the meat develops a cooked and sticky look after thawing. Because the muscle proteins and heme groups are displaced the thawing and freezing time is decreased and the meat doesn’t freeze uniformly unless in an oxygen depleted environment (vacuum sealed) (1) which may allow bacteria to re-proliferate and speeds oxidation of lipids. Glutamate/Glutamic Acid (not to be confused with gluten) are naturally present in amino acid rich proteins. Hydrolyzation is a process where proteins are broken down into their component amino acids (accomplished by many methods, including, obviously, HPP). Hydrolyzation releases natural glutamate into its “free form” which results in a by-product of 5-20% MSG. (20)

Lipid oxidation (peroxide and cholesterol) is dramatically increased after HPP especially in oxygen rich environments. Oxidative reactions make meat susceptible to loss of amino acids and decrease protein digestibility. The only ingredients known to limit oxidative damage in HPP products are rosemary, sage, EDTA, or egg white powder. Tocopherols, most commonly used in raw pet foods, are specifically listed as being ineffective. (1) Lipid peroxidation is the oxidative degradation of lipids which results in cell damage and rupture of red blood cell membranes which may be mutagenic and carcinogenic. Tests of toxicity of lipid hydroperoxides done on mice showed they did not survive past embryonic day 8, indicating that the removal of lipid hydroperoxides is essential for mammalian life. (2,3) Considering that most pets stay on a diet of one brand, and often one protein, for their entire life this science makes it seem life-threatening to use HPP meats as the primary source of any animals diet. Studies showed that lipid oxidation was ONLY slowed if the meat was pressure treated at 500MPa or above for 30-60 minutes at 20-70* C (68-158* F) (cooked) and vacuum sealed at the time of processing. Raw Pet Foods HPP for only 3-5 minutes at lower temperatures at 600MPa and do not commonly vacuum seal. Additionally, HPP meats are more stable and resistant to re-proliferation of pathogens ONLY if cooked prior to, or in conjunction with, HPP. (1)
Vitamin A has up to 100% loss at 87,000 psi. (1) Vitamin C has 30-40% decrease at only 400MPa and up to 70% at 600MPa (87,000psi) that is only limited by lowering oxygen concentrations. (5) Synthetically supplemented B Vitamins have a 30x greater rate of decay after HPP, especially Thiamine Monophosphate (TMP). (8) TMP deficiency results in the disease called Beriberi which may result in difficulty walking/incoordination, mental confusion, pain, strange eye movements, tingling, vomiting, increased heart rate, shortness of breath, enlarged heart, congestive heart failure and swelling of the lower legs. Lycopene (11) and Carotiniods (7) are damaged by HPP. HPP decreases the pH of meat products. (1) Excessively low pH levels may cause metabolic acidosis, which leads to acidemia, resulting in fatigue, headache, loss of appetite, coma or death. Whether the decrease of pH caused by HPP is significant enough to cause acidemia is debatable but a pet with existing health concerns such as urinary stones/crystals, infections, cancer, etc caused by low pH may be exacerbated by HPP.
HPP can inactivate microorganisms and enzymes as well as degrade and denature nutrients. (6) While blood and muscle tissue are void of DIGESTIVE and food enzymes metabolic enzymes are found in other tissues, including blood and muscle.  These enzymes are still part of the natural process of carnivore digestion, and are therefore beneficial for health. Just as cooking salad or fruit removes many beneficial enzymes and nutrients from foods, natural enzymes from all raw foods assist with balanced health in people and pets.
Studies have shown that polymer packaging material (plastic) that pet food is kept in is modified by high pressure. A significant migration of compounds from the plastic material into the food product has been observed. Traces of n-hexanal and some hydrocarbons have also been found by Schindler and others in 2010. (1) The Ecology Center lists “product packaging and food wrap plastic” under the section for Phthalates (DEHP, DINP, and others) and states that they are Endocrine Disruptors, linked to asthma, developmental and reproductive effects, release of dioxins and mercury, including cancer, birth defects, hormonal changes, decreasing sperm counts, infertility, endometriosis and immune system impairment. (4) Plastic fragments have never been found in raw pet foods.  However, plastic fragments have also never been found in plastic water bottles that were left in a 100* car or frozen, though research is wide-spread proving the health detriments of drinking water from a plastic bottle that has been heated or frozen.

Harlequin Dane
Dogs and cats are designed to tolerate pathogens
They have pathogen regulating, rather than digestive enzymes in their mouths, their short digestive tracts pass foods quickly, before they can harbor pathogens, their stomach acid is 1, far more acidic than a person. While a dog or cats system is fully capable of tolerating high levels of pathogens, in the case of illness it is unnecessary for the immune system to be forced to endure pathogens when it could be using metabolic and immune resources to heal. So the question becomes, is truly raw or HPP safer for an immune compromised pet??? Studies show that HPP is only highly effective in short and long term pathogen regulation when products are cooked or cured first, and then HPP. HPP alone does not always provide sufficient regulation of pathogens. HPP increases oxidation and free radicals, decreases enzymes and antioxidant capacity and destabilizes the amine matrix. Therefore, an already taxed immune system would have an increased free radical load, decreased contribution of enzymes to regulate health and decreased antioxidants to assist in regaining health.
The FDA, FSIS and FIC implemented a Zero Tolerance Policy (24) and “War on Pathogens” in 2009 (though FDA lists NO raw food recalls prior to 2009) on ALL raw pet foods. This means that non-HPP, completely raw pet foods, as well as HPP or other “stop-gap treated” foods, are allowed to have 0% pathogens in the food. Pathogen levels as low as .05% (far below levels that cause illness) will be recalled. For the consumer this means that untreated raw products are just as safe, if not safer than HPP. A non-HPP truly raw product must maintain superior standards because they must rely on the quality of well-sourced ingredients to be capable of testing negative for pathogens. Truly raw products would also maintain their natural bacterium that prevents pathogen proliferation once home with the consumer (22) while HPP pet food could purchase a Salmonella contaminated product and test free of pathogens after HPP, though bacteria needed to regulate the RE-proliferation of Salmonella were killed in the HPP process. It’s therefore safer to feed an immune compromised pet a fully raw product (that is unconditionally regulated for pathogens by FDA, FSIS and FIC) than it is to feed a HPP food product that burdens the body with lipid oxidation, decreased pH (metabolic acidosis), endocrine inhibitors, loss of Vitamin A, Thiamine, Vitamin C, Carotenoids, Enzymes, etc.
What if there ARE pathogens??? Wouldn’t HPP make the food safer?
Again, truly raw food is legally required to have substantially lower levels of pathogens than even Grocery Store meats for human food consumption. There have only been 5 recalls caused by the FDA’s Regulatory Offensive “War on Pathogens” that implemented microbiological sampling of over 2,000 raw pet food samples taken from retail stores between 6.1.2015-8.31.2015. FDA was instructed to enforce recalls on all products that tested positive for Salmonella, Listeria, E.Coli or Campylobacter. Despite the sampling of 2,000 raw (and HPP) pet food products only 5 (.002%) were recalled. 80% of the raw food recalls enforced in this time frame were popular HPP products. Only 20% (1 product (.0005%)) were caused by non-HPP, untreated raw pet food. Hundreds of other bags from the same truly raw batch were tested and no others came up positive.
Since 2007 there have been 7 recalls on Raw, untreated pet foods (no reported illnesses or death), 16 recalls on HPP pet foods (57% more than that of raw, untreated, non-HPP products), 2 recalls on Dehydrated raw pet foods, and nearly 300 recalls on Dry Kibble (Cooked Dog and Cat Food) and Cans (numerous reported illnesses and deaths), despite FDA’s active efforts to recall raw pet foods. (14)
E.coli is highly responsive to HPP, however since 2007 there has only been ONE recall of pet food for e.coli (dry food), making it a moot point for pet food regulation. PASTEURIZED dairy caused one recall. (17) Campylobacter – There is minimal reference to HPP’s ability to regulate Campylobacter. However, NO cases of campylobacter have ever been associated with pet food recall, making it a minimal concern. (18) Listeria monocytogenes has been observed to have a higher survival rate in cooked and HPP meat than in raw meats. (Simpson and Gilmour 1997) (1) From 2011-2016 there have been 10 Outbreaks caused by Listeria. None of them have been caused by pet products, 6 were caused by PASTEURIZED dairy. (15) Salmonella – In September of 2015 Dr. William James, a 28 year Chief Veterinarian of FSIS in charge of pathogen and residue sampling published a document showing his disappointment in FSIS’s ability to decrease Salmonella in food products since 2000 despite changes in policy. He states that FSIS will not change their regulatory strategy for Salmonella, despite its failures. (13) Since 2006 there have been 60 outbreaks caused by Salmonella, TWO of which were caused by COOKED, DRY PET FOOD (none from raw). (16)

Kicking Auss
(1) “New Insights into the High-Pressure Processing of Meat and Meat Products.” H. Simonin, F. Duranton, M. de Lamballerie, Comprehensive Reviews in Food Science and Food Safety, May, 2012. 10.1111/j.1541.4337.2012.00184
(2) Lipid peroxidiation – DNA damage by malondialdehyde. Marnett LJ. Mutation research 1999 Mar 8;424(1-2):83-95
(3) Muller, F.L. Lustgarten, M.S., Jang, Y., Richardson, A. and Van Remmen, H. (2007), “Trends in oxidative aging theories”. Free Radic. Biol. Med. 43 (4): 477-503 doi:10.1016/j.freeradbiomed.2007.03.034. PMID17640558
(4) Ecology Center, “Plastic Task Force Report” Berkeley, CA 1996
(5) Indrawati O., Ven der Plancken I., Van Loey A. Hendricks M., “Does High Pressure Processing Influence Nutritional Aspects of Plant Based Systems?” Center for Food and Microbial Technology, Food Science and Technology 2007
(6) M. Hendrickx, L. Ludikhyze, I. Van den Brock, C. Weesmaes, “Effects of High Pressure on enzymes related to food quality” Trends in food Science Technology, 9 (1998), PP. 197-203
(7) A. Fernandez Garcia, P. Butz, B. Tauscher, “Effects of high pressure processing on carotenoid extractability, antioxidant activity, glucose diffusion and water biding of tomato puree.” Journal of Food Science, 66 (7)(2001), pp 1033-1038
(8) P.Butz, A. Bognar, S. Dieterich, B. Tauscher, “Effect of high-pressure processing at elevated temperatures on thiamin and riboflavin in pork and model systems.” Journal of Agriculture and Food Chemistry, 55(4)(2007), pp 1289-1294
(9) So YT, Simon RP. Deficiency diseases of the nervous system. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley’s Neurology in Clinical Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 57. Updated 2014.
(10) W. MEssens, J. Van Camp, A. Huygebaert, “The use of high pressure to modify the functionality of food proteins” Trends in Food Science and Technology, 8(1997), pp 107-112
(11) W. Qui, H. Jiang, H. Wang, Y. Gao, “Effect of high hydrostatic pressure on lycopene stability” Food Chemistry, 97 (2006), pp 516-523
(12) W. MEssens, J. Van Camp, and H. Huyghebaert (1997), The Use of high pressure to modify the functionality of food proteins. Trends in Food Science and Technology (Vol. 8)
(13) FSIS’ salmonella policies: actions vs accomplishments (paid document)
(14) Search: “_____ recalls”
(22) Food Industry Counsel, LLC, FDA’s War on Pathogens, Criminal Charges for Food Company Executives and Quality Assurance Managers, S. K. Stevens, Esq.
(24) K&L Gates Docket No FDA-2010-D-0378; Draft Compliance Policy Guide Sec. 690.800, Salmonella in Animal Feed (75 Fed. Reg. 45,130 (August 2, 2010) Zero Tolerance Pathogens

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