High-pressure processing (HPP) for the purpose of extending the shelf life of refrigerated foods is rapidly expanding globally. The uptake of HPP over the past 20 years by the food and beverage industry has been extraordinary. HPP involves holding the subject food or beverage under high hydrostatic pressure (> 400 MPa) for several minutes to reduce the material’s pathogens and spoilage flora. Scientists worldwide have investigated the use of HPP food applications for more than 50 years. According to Dietrich Knorr,[1] the first reports of the effect of high pressure on organisms were likely reported in 1883 by Adrien Certes, who found viable bacteria in water samples collected at a depth of 5,100 meters (50 MPa). Certes continued his investigations using a pressure apparatus that was reportedly capable of achieving pressures as high as 600 MPa. High hydrostatic pressure treatment of food by B. H. Hite was first reported in 1899. This is also the first time that a reduction in spoilage flora using HPP was reported. The first commercial products treated by HPP were introduced in Japan in 1990. In 1999, a very successful product, HPP-treated guacamole, was launched in U.S. markets.[2]

HPP Achieves High-Profile Success
In 2009, workers at the National Center for Food Safety and Technology submitted a first-of-its-kind scheduled process for high pressure-assisted thermal sterilization (PATS). The PATS process filing, as accepted by the U.S. Food and Drug Administration (FDA), was designed to achieve commercial sterility in a low-acid canned food (LACF) product. The PATS process was confirmed capable of eliminating pathogenic spores and other spoilage flora from LACF products. However, HPP’s greatest success to date is its use to save the U.S. hot dog and deli meat business. Between 1997 and 1999, there were several, and in rapid succession, massive recalls involving millions of pounds of these products in the U.S. due to Listeria contamination. The use of HPP as a post-processing intervention all but eliminated this public health challenge and restored consumer confidence in this product category.

It is clear that of the many novel and non-thermal preservation methods to emerge in the last decade, HPP is the most useful and viable method for extending the shelf life of refrigerated foods. It also holds promise as a method to achieve commercial sterility of low-acid and acidified food products. Doing so will involve an evolution in processing equipment to accommodate heating, validation of food safety, and confirmation of regulatory compliance. Acidified and low-acid foods, by regulation, require the involvement of a “processing authority” (defined below) in establishing scheduled processes. Advancing HPP technology in the U.S. will also require the expertise of a processing authority.

Enter the Processing Authority
A processing authority is a person who has expert knowledge of thermal processing requirements for low-acid foods packaged in hermetically sealed containers, or has expert knowledge in the acidification and processing of acidified foods. Knowledge can be obtained by education or experience or both. Expert implies experience, knowledge, and achievement as well as recognition as an authority on a subject, usually by one’s peers. Anyone who is establishing scheduled processes must have adequate facilities for making the appropriate determinations. Anyone who is evaluating processes which are less than the scheduled process (process deviation) must utilize procedures recognized by competent processing authorities as being adequate to detect any potential hazard to public health.”[3] It is important to note that the regulations are intended to govern the end product of a processing authority’s work rather than that person’s qualifications. However, if the Center for Food Safety and Applied Nutrition [HFS-617-Division of Hazard Analysis and Critical Control Points (HACCP), Regulatory Food Processing and Technology Branch] is unfamiliar with the processing authority, they may review their qualifications and the procedures and methods utilized to evaluate the adequacy of the final work product.

In the U.S., the role of the processing authority in the production of thermally processed, low-acid, and acidified canned food is unambiguous.[4–6] The concept of the processing authority has been enshrined in FDA regulations since 1973. The situation in other regions of the world, however, is much less clear. Codex, for example, has in larger measure adopted and incorporated the LACF regulations in its Code of Hygienic Practices for Low Acid and Acidified Low Acid Canned Foods.[7] The Codex standard does not have an explicit requirement for a processing authority but requires that scheduled processes for low-acid foods should originate from “competent persons.” And while the nomenclature between the FDA and Codex regulations is different, the activities and expectations of “competent persons” are implicitly, it would appear, the same as those of the LACF’s processing authority. In Australia and New Zealand, where both CAC/RCP 23-1979 and FDA’s LACF regulations have been adopted, the requirement is for an “approved person” to develop scheduled processes for LACFs. But, unlike the U.S. and Codex, these two countries have mandatory training and certification requirements for their approved persons.

On July 2, 1971, FDA released a public warning after learning that a Westchester County, NY, man had died and his wife had become seriously ill from botulism after partly eating a can of Bon Vivant vichyssoise soup.[8,9]

The company began a recall of the 6,444 cans of vichyssoise soup made in the same batch as the can that was confirmed to be contaminated. FDA then said that the company’s processing practices made questionable all products packed by the company and extended the recall to include all Bon Vivant soup—more than a million cans in all. FDA ordered the shutdown of the company’s Newark, NJ, processing plant on July 7, 1971. Ultimately, 5 cans of soup, out of 324, were found to be contaminated with botulinum toxin, all in the initial batch of vichyssoise soup that was recalled. Bon Vivant filed for bankruptcy and ultimately went out of business.

In August 1971, canned chicken vegetable soup produced by the Campbell Soup Company tested positive for botulinum toxin. This finding resulted in the recall of some 4,799 cans of soup from the implicated batch. This incident is reported to have cost Campbell $5 million ($27.4 million in today’s dollars) and damaged the company’s reputation.

These two public health incidents served to incentivize FDA and the National Canners Association to collaborate in promulgating the LACF regulations that were first adopted in 1973 and revised in 1979. A hallmark of these regulations is the creation of the processing authority.

The concept of the processing authority in the U.S. was expanded beyond low-acid and acidified canned foods by the California Almond Board and the U.S. Department of Agriculture’s Agriculture Marketing Service in 2007 with establishment of the California Almond Marketing Order. The marketing order requires the use of a processing authority for validation of pasteurized or otherwise treated almonds to confirm a 4-log reduction of Salmonella. The marketing order states that the role of the processing authority, in the context of its program, “is modeled after the FDA’s LACF requirements.” This action taken by a nongovernmental organization was a major development in the history of the processing authority in the U.S. 

Roles of the Processing Authority
Ultimately, a processing authority must establish thermal processes.[10] Without a properly established process, process control at the processor level is useless. In other words, you cannot verify a process that has not been validated. Establishing processes requires, among other things: 1) considerable knowledge about product characteristics and the effect of each processor’s equipment and procedures on those characteristics of importance to heat penetration; 2) experience in conducting heat penetration, temperature distribution, thermal-death time studies, and other scientific methods; and 3) the ability to determine through evaluation of data generated by these studies and tests that sufficient testing has been accomplished to identify all possible critical factors that could affect the heating characteristics of the product and the safety of the final product. It is often necessary for a processing authority to recognize the inadequacies or inexperience of a processor to provide the processor with sufficient information to ensure understanding of what factors are critical for achieving food safety. These same responsibilities should apply whether the processing authority is establishing a thermal process or another food stabilization method. These fundamental precepts of food safety science remain valid for non-thermal methods and for other food processing techniques and applications.  

Novel and Non-Thermal Processing Technologies
LACF regulations in the U.S. are unequivocal in that a processing authority is required for processors engaged in processing certain classes of high-risk, thermally processed canned foods. When processing a food with a pH greater than 4.6 and a water activity (Aw) exceeding 0.85 that is intended for nonrefrigerated distribution, a processing authority is required. By contrast, the regulations governing other classes of foods, processed by other than thermal methods, are less emphatic. For example, a low-acid or acidified food, food held in a hermetically sealed container, food processed using HPP, and food intended for refrigerated distribution would not require, by regulation, the involvement of a processing authority. Another example for consideration might include an HPP-processed LACF (Aw < 0.85) that is intended for ambient distribution. This food would not require a scheduled process and therefore no mandatory involvement of a processing authority. Another intriguing example is that of an aseptically packaged, acidified, low-acid food (pH < 4.6) treated by a pulsed electric field (PEF) that is also intended for ambient storage and distribution. This product and process combination would not necessarily be absolved of the requirement for a processing authority, even though a PEF is considered a non-thermal process. This is a unique, if not novel, set of product and processing conditions, and therefore the processor would be advised to consult with a processing authority and also FDA. There are a host of other novel preservation methods that have emerged within the past 10–15 years that will also need to be evaluated before they are accepted for use in the production of human food, including atmospheric plasmas, light-emitting diodes, high-intensity pulsed light, power ultrasound, and low-energy electron irradiation.

High hydrostatic pressure in combination with heat, involving either an acidified or low-acid food that is intended for ambient distribution, must involve the expert services of a processing authority. PATS processes, for example, are regarded by FDA as thermal processing techniques that require a scheduled process. The LACF regulations were modified in 2009, following the first-ever submission of a scheduled process for PATS, to accommodate this method of food sterilization.

When the time and temperature components of a pressure-assisted process do not conform to those customarily used for thermal sterilization of low-acid food products, this process too should require the involvement of a processing authority. For example, the pressure-enhanced sterilization (PES) process (accepted by FDA in 2015) relies on relatively mild temperatures (110 °C/230 °F) and 700 MPa (for 3 minutes) to achieve commercial sterility in a low-acid, heterogeneous food system. This process (while not representative of the classical 12 D thermal process) was, with the assistance of a processing authority, accepted by FDA even though the agency noted, in its letter of no objection, “this is not a thermal process.” A compelling argument could be made that PES is a pressure-driven, non-thermal process and, as such, a process filing with the processing authority is not required. As of now, this is a gray area in the LACF regulations. For the time being, processors using similar pressure-driven thermal processes are advised to work with a processing authority and to also file a scheduled process with FDA. 

Compliance Requirements for Processors
Under the LACF regulation, 21 C.F.R. 108.35(c)(3) and 108.25(c)(3) are written fundamentally to ensure that valid processes are used to mitigate the food safety risk that may be associated with thermally processed low-acid and acidified canned foods.

These sections require all LACF and acidified food processors to comply with the mandatory requirements of 21 C.F.R. 113 and 114, including registration of processing plants, filing of scheduled processes, control of critical factors, and adherence to the filed processes. Information concerning processes and other data provided to the agency are regarded as trade secrets. FDA’s request and examination of such information does not constitute approval. However, when it is the agency’s determination that the submitted data are insufficient or inconsistent with mitigating the risk to public health, FDA will reject the submitted process. On occasion, the agency will issue a letter of no objection, which is also based on its evaluation of the submitted process information. Articulating the process definition, elaborating on the critical factors, and identifying the process control measures are the work of the processing authority. The benefits of the LACF regulations and the requirement for a processing authority are clear. The incidents of botulism in commercially canned food, since 1973, have plummeted to nearly zero.

The Hazard Analysis and Risk-Based Preventive Controls rule of the Food Safety Modernization Act requires that critical control points of the company’s food safety plan are overseen by a Preventive Controls-Qualified Individual (PCQI): a “qualified individual who has successfully completed training in the development and application of risk-based preventive controls at least equivalent to that received under a standardized curriculum recognized as adequate by FDA or is otherwise qualified through job experience to develop and apply a food safety system.”[11] It is possible to earn the PCQI distinction after receiving a mere 2.5 days of training. By contrast, it takes many years of training and experience to become a recognized processing authority. While PCQIs are not processing authorities, they do function to preserve process assurance (food safety assurance) for those categories of food that do not explicitly have a regulatory mandate for a processing authority. For example, high pressure-processed apple juice (pH 4.5) intended for nonrefrigerated distribution, would not have a statutory requirement for the involvement of a processing authority. In this case, the PCQI would be responsible for confirming that the applied process resulted in the regulatory required minimum 5-log reduction of acid-adapted Escherichia coli consistent with the requirements of the Juice HACCP regulation. The distinction between the roles and responsibilities of the PCQI and processing authority is confusing in some circumstances and may lead to unqualified individuals assessing the safety of foods processed using novel, unregulated preservation methods.

A processing authority should be involved at least in the early research and design phases when novel preservation methods are considered. Their knowledge of microbiology, the processing equipment, and process control procedures will enable an assessment of both the regulatory requirements and the potential risk to public health. This brings to mind the story of the wealthy entrepreneur who was so impressed with HPP technology that he purchased line time and developed a potentially dangerous product that he intended to process by this method. Ultimately, his plans were intercepted by persons knowledgeable in food processing and HPP, and a public health crisis was prevented.  

Because of the newness of HPP and the myriad yet-unanswered questions, unsettled regulatory status, and vagaries in the science pertaining to public health outcomes when using HPP, it is advised that perspective processors should engage with a processing authority for both technical and regulatory guidance.    

1. Knorr, D. “Hydrostatic Pressure Treatment of Food: Microbiology,” in New Methods of Food Preservation, ed. G Gould (NY: Springer, 1995).
2. Brown, AC, Understanding Food: Principles and Preparation, 3rd ed. (Cengage Learning, 2007).
3. 21 C.F.R. 113.83 and 21 C.F.R. 113.89.
4. www.fda.gov/low-acid-canned-food-manufacturers-part-1-adminstrative-proceduresscheduled-processes.
5. www.fda.gov/low-acid-canned-food-manufacturers-part-2-processesprocedures.
6. www.fda.gov/low-acid-canned-food-manufacturers-part-3-containerclosures-1198.
7. CAC/RCP 23-1979.
8. Lyons, PJ. 2007. “In a Beef Packager’s Demise, a Whiff of Vichyssoise.” The New York Times.
9. Montgomery, PL. “Botulism Death in Westchester Brings Hunt for Soup.” The New York Times, no date.
10. 21 C.F.R. 113.83.
11. www.fda.gov/food/food-safety-modernization-act-fsma/frequently-asked-questions-fsma.

Larry Keener, CFS, PA, PCQI, is the principal of International Product Safety Consultants Inc., based in Seattle, and a member of the editorial advisory board of Food Safety Magazine.