High Pressure Pasteurization ≠ Raw


Research from Answers Pet Food

There have been varying opinions within the pet food industry concerning the process of High Pressure Pasteurization (or Processing), often referred to as HPP. Rather than base our decision on opinions and emotions, the Answers’ team chose to review scientific data and build our knowledge on the research and conclusive facts about this technology. There are many valuable research papers published in reputable scientific journals regarding this technology. We have taken the opportunity to evaluate this research and outline the most relevant conclusions for the concerned pet owner to review.

Based upon our knowledge of the value of a raw diet we understand the importance of limited processing on the meat to deliver the most nutritionally dense food to our pets. In our modern society this can be a challenging task, especially if we cannot raise and butcher our own livestock. Any processing step can have a deteriorating impact on the chemical composition of the meat; including grinding, mixing, vacuum stuffing and freezing. At Answers we do our best to minimize processing our raw materials so that we can deliver the most complete raw product as possible.

When dealing with raw meat there is always an inherent risk from microbial contamination which is a natural part of the animal’s physiology. When processing a raw product it is very important to have strict controls in place to minimize this risk. There are several ways to address this. Generally, the food industry has simply recommended a heat (or kill) step to at least 165°F to eliminate the risk of pathogenic bacteria. However, this obviously negates the benefit of a raw diet since this step denatures proteins and active enzymes as well as depletes vitamins. Another, more recently emerging technology that has been employed to address microbial contamination in food is High Pressure Processing or HPP.

HPP began as a new technology in the early 1960’s in Japan as an alternative to heat processing, in particular for making protein gels [2]. This technology is now being employed in North America as an alternative to heat processing for reducing bacterial contamination in many foods and beverages. This process lends itself well to high acid, homogenously blended foods [4]. It has been most advantageous in the fruit juice and fruit puree industry because it can inactivate ripening enzymes, thereby extending the shelf life of the product while having less impact on the vitamin and nutrient content of the fruit [4]. It has been shown that HPP does inactivate most of the vegetative bacteria in the product [7], but not without a cost to the proteins, enzymes, vitamins and essential fatty acids in the food, especially in meats. The following statements have been cited from just a few of the many published scientific papers.

  • Even moderate pressures (<150 MPa) have been shown to cause disassociation of proteins into their sub-units. At pressures of 300-400 MPa, the major proteins found in animal muscle, myosin and actin, as well as many sarcoplasmic proteins are denatured. At pressures ≥ 400 MPa, myoglobin becomes irreversibly denatured [11].
  • The tertiary and quaternary structures of globular proteins are readily disrupted. The carboxyl groups on polysaccharides and proteins become ionized during high pressure treatment. It was demonstrated that the aggregate and conformational behavior of BSA (bovine serum albumin) in a dilute solution (at neutral pH) was considerably affected by high pressure treatment (>300MPa) [10].
  • Because high pressure treatment has been shown to lead to denaturation, aggregation and gelation of proteins, it has been used as an alternative method to heat for forming protein gels [3, 6].
  • Molina, Defaye and Ledward, using DSC (differential scanning calorimetry), showed that at pressures above 400MPa, HP begins to denature the proteins and as pressure increases the degree of denaturation increases. They also concluded that it is possible for proteins undergoing HP treatment to unfold, aggregate and precipitate resulting in high molecular weight aggregates, and create gels differing from the molecular interactions involved. [1]

At Answers we have chosen to take a different approach to provide a high quality, nutritionally dense, microbially responsible raw food product. First and foremost the best approach to provide a low risk, raw food from pathogenic contamination is by starting with healthy, high quality, properly cared for livestock. Many of the reasons the meat in this country contains the pathogenic bacteria loads it does is directly due to the crowded housing conditions, poor hygiene, improper feeding and handling techniques of livestock animals. At Answers we understand the benefits of using livestock that is pasture fed, and never exposed to synthetic hormones and antibiotics. Studies show that healthy, pastured livestock will shed significantly less E. coli [9]. Also, when cows are grass fed there is reduced risk of Salmonella infections [8]. Secondly, butchering and post butcher handling must be closely monitored and controlled to limit contamination.

Answers uses intervention steps to reduce the load of potentially harmful bacteria. We also subscribe to the method of competitive inhibition [5] as a more suitable method for controlling the potential growth of pathogenic bacteria in a raw product. We add beneficial micro-flora (pro-biotics) through our fermented decaffeinated Kombucha tea. This provides a reduced pH as well as a competitive microbial environment, reducing the risk for pathogenic bacteria growth.

While HPP offers the benefit of eliminating vegetative bacteria, both pathogenic and beneficial, it does not kill the spores that many bacteria can form as a means of hibernation when they are faced with a hostile environment [7]. If the post HPP treated food environment becomes favorable for microbial growth then these spores can freely proliferate, because there are no other vegetative bacteria in the environment to compete with, and the potential for their numbers to grow quickly has now greatly increased.

In 1906, when the pasteurization process of raw milk was first introduced, advocates of the technology touted the process as having no deleterious effects on the quality and nutritive value of the milk. By 1919 there was already strong evidence to disprove this theory. Data showed an increased sensitivity of pasteurized milk to TB infection as well as an increase in TB infections within London populations who regularly drank pasteurized milk [8].

History has clearly illustrated the many times our human race has attempted to improve upon Mother Nature. Yet time and time again we are forced to learn the hard way that this attempt often results in negative, if not detrimental, effects to the health and well being of our population.


  • Elena Molina, Aklile B. Defaye, Dave A. Ledward. (2002). Soy Protein Pressure Induced Gels. Food Hydrocolloids. 16, 625-632
  • Isao Hayakawa, Junko Kajihara, Keisuke Morikawa, Mitsuhiko Oda, and Yusaku Fujio. (1992). Denaturation of Bovine Serum Albumin (BSA) and Ovalbumin by High Pressure, Heat and Chemicals. J. of Food Science, Vol. 57, no. 2, 288-292.
  • C. Cheftel. (1992) Effects of High Hydrostatic Pressure on Food Constituents. In High Pressure and Biotechnology, Vol. 224 (pp. 195-209).
  • Hendrickx, L.Ludikhuyze, I.Van den Broeck and C. Weemaes. (1998). Trends in Food Science & Technology, 9: 197-203.
  • Masud, A.H. Soomro and Kiran Anwaar. (2002) Role of Lactic Acid Bacteria (LAB) in Food Preservation and Human Health-A Review. Pakistan J. of Nutrition 1 (1): 20-24.
  • Lopez-Fandiño, A.V. Carrascosa, and A. Olano. (1996). The Effects of High Pressure on Whey Protein Denaturation and Cheese-Making Properties of Raw Milk. J. Dairy Sci., 79: 929-936.
  • Raghupathy Ramaswamy, V.M Balasubramaniam, Gönül Kaletune. High Pressure Processing. Fact Sheet for Food Processors. The Ohio State University Extension. Food Science and Technology.
  • Ron Schmid, ND. (2003). The Untold Story of Milk, Green pastures, Contented Cows and Raw Dairy Foods. New Trends Publishing. Washington DC.
  • R. Callaway, R.O. Elder, J.E. Keen, R.C. Anderson, and D.J. Nisbet. (2002). Forage Feeding to Reduce Preharvest Escheria coli Populations in Cattle, a Review. Food and Feed Safety Research Unit, Southern Plains Agricultural Research Service, USDA, College Station, TX.
  • Vanda B. Galazka, Dave A. Ledward, Ian G. Sumner, and Eric Dickenson. (1997). Influence of High Pressure on Bovine Serum Albumin and Its Complex with Dextran Sulfate. J. Agric. Food Chem. 45: 3465-3471
  • Messens, J. Van Camp and A. Huyghebaert. (1997). The Use of High Pressure to Modify the Functionality of Food Proteins. Trends in Food Science & Technology. [Vol. 8].

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  • Billie Claire Darby
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