High pressure processing (HPP) treats a food with pressure. In FDA's juice hazards guidance, pressure in excess of 30,000 to 45,000 psig is the principal anti-microbial agent, and the juice HACCP questions and answers name high pressure as a 5-log control measure. The hold, the package, and the rule are set for that food.

What the HPP process is

FDA's juice hazards-and-controls guidance, in section 5.33, states: "High pressure processing, a technology in which pressure (in excess of 30,000 to 45,000 psig) is the principal anti-microbial agent, has been shown to be effective in reducing vegetative pathogens." The same paragraph states that both semi-continuous and batch processes have been developed, and recommends that process time and pressure be critical limits for both.

FDA's juice HACCP questions and answers describe the 5-log pathogen reduction performance standard as a process that will achieve at least a 100,000 fold decrease in the number of microorganisms. Question 37 lists high pressure as an example of one control measure that has been shown to reduce the pertinent microorganism by at least 5-log. The questions and answers call that route a way to achieve the reduction without pasteurizing the product.

21 CFR 120.24(a) is the juice rule behind that standard. Processors of juice products shall include, in their HACCP plans, control measures that will consistently produce, at a minimum, a 5 log (i.e., 10⁵) reduction, for a period at least as long as the shelf life of the product when stored under normal and moderate abuse conditions, in the pertinent microorganism. The pertinent microorganism is "the most resistant microorganism of public health significance that is likely to occur in the juice." 21 CFR 120.1(a) applies this part to any juice sold as such or used as an ingredient in beverages. Juice, in that section, means the aqueous liquid expressed or extracted from one or more fruits or vegetables, purees of the edible portions of one or more fruits or vegetables, or any concentrates of such liquid or puree.

Two juice processors are exempt from the 5-log paragraph in § 120.24(a). One is a juice processor subject to 21 CFR Part 113 or Part 114. The other is a juice processor using a single thermal processing step sufficient to achieve shelf-stability of the juice, or a thermal concentration process that includes thermal treatment of all ingredients, provided the written hazard analysis includes a copy of the thermal process used to achieve shelf-stability or concentration. A retort, under 21 CFR 113.3, is any closed vessel or other equipment used for the thermal processing of foods; the juice hazards guidance places high pressure processing with other non-thermal treatments, and that thermal-process rule is covered in what retort processing is.

The hazards guidance states that treatment technologies that do not use a source of radiation or a chemical agent, for example high pressure processing, are not likely to require FDA approval, and that you should verify any such assumption with your process authority. The same guidance states that the process used for pathogen control must be validated under 21 CFR 120.11. Section 120.11(b) requires validation that the HACCP plan is adequate to control food hazards reasonably likely to occur, at least once within 12 months after implementation and at least annually thereafter, or whenever a change could affect the hazard analysis or alter the plan. The listed changes include product formulation, processing methods or systems, packaging, and finished-product distribution.

FDA's draft guidance on preventive controls for human food, Chapter 4, states that the draft, when finalized, will represent FDA's current thinking, that it does not establish any rights for any person, and that it is not binding on FDA or the public. In the HPP section, the draft states that microorganisms vary in their sensitivity to high pressure, and that a user should consider the organism of concern, the product characteristics, and whether the product is to be refrigerated or shelf stable. It states that bacterial spores are the most pressure-resistant biological forms known, that spores resist inactivation by high pressure alone, and that most require the addition of heat or some other mechanism to achieve appropriate levels of destruction. It states that, because of this, the best candidates for HPP continue to be acid foods and foods that will be refrigerated following processing, which provide control of sporeformers.

Ohio State University Extension states that pressure treatment at ambient or chilled temperatures does not inactivate bacterial spores, and that treated products are typically distributed under a refrigerated environment. The fact sheet also states that an insufficient intensity of pressure treatment may only injure a proportion of the bacterial population, and that the injured bacteria may then recover during storage. It states that high pressure above 60,000 pounds per square inch inactivates most vegetative bacteria, but that spores survive pressure treatment at ambient temperatures. "Most" is the fact sheet's word. It is not a statement that every microorganism is inactivated.

How the HPP process works

The draft guidance describes batch processing this way: the food is packaged in a flexible or semi-flexible package, placed into a chamber, and immersed in water or some other pressurizing fluid, then subjected to the high pressure for a time of 1 - 20 minutes, depending on the temperature and pressure. The chamber is then depressurized and the product removed. The draft states that foods using HPP are being processed by batch systems, and that semi-continuous, continuous, and pulsed systems have been described elsewhere.

Ohio State University Extension describes the same batch shape from the package inward. The product is packaged in a flexible container, such as a pouch or a plastic bottle, and loaded into a sample basket. The basket is loaded into a high-pressure chamber filled with a pressure-transmitting fluid such as water. A pump pressurizes that fluid, and the pressure is transmitted through the package into the food. The fact sheet states that the product is held under pressure for a specific time, usually 2–5 minutes, before depressurization, and that product temperature then returns close to its initial value. The "1 - 20 minutes" sentence and the "usually 2–5 minutes" sentence are two documents' descriptions. Neither sentence is the critical limit for a SKU. The juice hazards guidance recommends that process time and pressure be the critical limits, and states that temperature may or may not need to be a critical limit.

That guidance also states that the temperature of the product does increase during high pressure processing. The increase depends on the composition of the food, the initial temperature of the product and vessel, the pressure transmitting fluid for batch systems, and the time the product is held at the processing pressure. Many systems do not control product temperature during treatment, and the temperature tends to decrease with time because of heat loss to the vessel. For many systems, a minimum initial temperature of the product or vessel may be specified. For batch systems, the guidance recommends that changes in the composition of the pressure transmitting fluid be controlled and checked periodically. Ohio State states a transient temperature rise of 3 degrees Celsius per 100 MPa from adiabatic heating. That ratio is the fact sheet's figure for the rise during pressurization.

The documents do not use one pressure figure. The juice hazards guidance describes the technology as pressure in excess of 30,000 to 45,000 psig. The draft guidance states that high pressure processing of foods requires pressures of 400 to 700 MPa, or 4000 - 7000 bars (58,000 - 101,000 psig), and that most commercial food industry applications use pressures in the range of 600 to 700 MPa. Ohio State describes HPP as food subjected to elevated pressures up to 87,000 pounds per square inch, or 6,000 atmospheres, or 600 MPa, at ambient or chilled temperatures. Those are the figures printed in each document. The figure for a SKU is the critical limit established for that food, that package, and that organism, not a number copied from a different product.

FSIS Directive 5000.15 lists critical operational parameters an HPP process may include: process pressure, process hold time at pressure, time to achieve pressure, initial product temperature, treatment temperature, and decompression time. The directive tells inspectors to verify that an establishment evaluates factors such as pH, water activity, composition, packaging, or preservatives when it sets those parameters for each product type, and that there is a defined process for every type of product treated. It states that HPP is generally more effective in reducing microbial pathogens when the water activity of a product is increased, and that as pH is lowered, most microorganisms become more susceptible to HPP treatment. It gives, as an example, that an HPP process for RTE chicken breast may be shorter when the same product is breaded. That example is the directive's example. It is not a time for every chicken product.

Ohio State states that acidic foods with a pH less than 4.6 are particularly good candidates. That sentence is the fact sheet's candidate statement. Whether a food is a low-acid food under 21 CFR 113.3 is a separate definition, covered in the retort note. The fact sheet states that foods with entrapped air, and it names breads, cakes, mousse, strawberries, and marshmallows, are not suitable, because they might deform under pressure. It states that low-moisture foods, and it names spices, powders, and dry fruits, are not suitable, because the microbial lethality of pressure diminishes under low-water activity. Those lists are the fact sheet's lists.

On the package, the fact sheet states that the food and the packaging may undergo a 15% volume reduction and then return to its original volume on depressurization, so the package has to withstand that transient reduction. It states that at least one interface of the package needs to be flexible enough to transfer pressure, and that rigid containers such as glass bottles or tin cans cannot be used, because they cannot transmit the pressure to the food. It names polyethylene terephthalate, polyethylene, polypropylene, and ethylene vinyl alcohol copolymer as commonly used materials. The juice hazards guidance does not repeat that material list. Ask the plant which package the validation used.

What an HPP machine is

An HPP machine, in the documents above, is the equipment that runs that chamber. The juice hazards guidance calls the equipment high pressure processing systems and refers to the surrounding pressure vessel and, for batch systems, the pressure transmitting fluid. The draft guidance calls it an HPP system and a chamber. Ohio State calls it commercial-scale equipment and states that vessel volumes range from 35 to 525 liters. The fact sheet also describes a bulk option for a large volume of beverages: the liquid goes into a pre-sanitized polymer bag of up to 500 liters, about 90% of the pressure vessel, and after processing the liquid is discharged to an aseptic tank and then to a filling line. That bulk description is the fact sheet's description of a different loading method. It still has to be read against the rule for the SKU. For juice, § 120.24(c) requires the 5-log treatment and final product packaging in a single production facility operating under current good manufacturing practices. FDA's questions and answers state that the entire 5-log reduction must be accomplished within a single production facility.

The draft guidance states that high pressure processing requires very specialized and costly equipment. It does not state a price.

For amenable meat and poultry, FSIS Directive 5000.15 states that HPP is considered preparation or processing of meat or poultry products as defined in 9 CFR 301.2 or 9 CFR 381.1, and that FSIS inspection is required at all facilities that perform HPP on amenable meat or poultry products, whether the process is used for food safety or for food quality purposes. The directive states that HPP is an antimicrobial treatment that does not require prior approval from FSIS for use on meat, poultry, and egg products, and that HPP subjects food to elevated pressures to inactivate microorganisms for food safety or quality purposes. That sentence is the directive's description of the treatment. It is not a finding about a particular lot. The same directive states that HPP can be performed on both raw and ready-to-eat products.

Juice, meat, and a label word

The off-site question is not the same in the two programs. For juice, § 120.24(b) says the 5-log treatments are applied directly to the juice, except that citrus juice processors may use treatments on fruit surfaces, provided the reduction begins after culling and cleaning and is accomplished within a single production facility. Section 120.24(c) puts final packaging in that same facility. For meat and poultry, FSIS Directive 5000.15 describes producing establishments that send packaged product to another official establishment for HPP. When that step is a critical control point, the directive points inspectors to the monitoring, verification, and corrective-action records in 9 CFR 417.5(a)(3) and 417.5(b), and it states that the producing establishment does not complete pre-shipment review until it receives documentation that the critical limits and critical operational parameters were met.

The directive's examples of a critical control point include HPP as a post-lethality treatment to control Listeria monocytogenes in a ready-to-eat product, and HPP as a critical control point to control biological hazards such as Salmonella or Campylobacter in comminuted poultry. Those are the directive's examples. When HPP is used to reprocess an adulterated ready-to-eat product, the directive states minimum levels of lethality: a 5-log reduction of Listeria monocytogenes, a 5-log reduction of Salmonella for meat products, and a 7-log reduction of Salmonella in poultry products. Those figures are the reprocessing figures in the directive. They are not the juice performance standard, and they are not a standing process for every ready-to-eat item.

A juice label has a separate constraint. FDA's questions and answers state: "Pasteurization is a heat treatment sufficient to destroy pathogens. Therefore, to be labeled as 'pasteurized,' a juice must be heat treated to destroy pathogens." Question 37 places high pressure on the list of ways to achieve a 5-log reduction without pasteurizing. Ohio State describes HPP as a food pasteurization method. That description and the juice labeling answer use the word differently. A brand that wants the word "pasteurized" on a juice label is in the questions-and-answers statement, which requires a heat treatment.

Questions to ask a co-packer

NXTCPG's published Source & produce work is ingredient sourcing, co-manufacturer selection, and quality and scale readiness. The site does not state an HPP machine, a vessel, or a pressure process operated by NXTCPG. Who manufactures, who packs, who owns the formula, and what a pilot must show are in how to choose a co-packer. Current good manufacturing practice for the facility is a separate question, in what cGMP is. The thermal process for a low-acid food in a hermetically sealed container is in what retort processing is.

  • Which rule covers this SKU: 21 CFR Part 120 for a juice, the Part 113 or Part 114 exemption in § 120.24(a), or FSIS Directive 5000.15 for an amenable meat, poultry, or egg product?
  • For juice, what is the pertinent microorganism, and which validation shows the 5-log reduction for a period at least as long as the shelf life under normal and moderate abuse conditions?
  • For juice, is the treatment applied to the juice? If any part of a citrus reduction is a surface treatment, where do culling, cleaning, and the single-facility limit in § 120.24(b) sit?
  • For juice, do the 5-log treatment and final packaging happen in one production facility, as § 120.24(c) requires?
  • What are the critical limits for process time and pressure? Is temperature a critical limit, or is a minimum initial temperature specified? For a batch system, how is the pressure-transmitting fluid checked?
  • Who evaluated the process, and what is the date of the last HACCP-plan validation under § 120.11(b), including any validation after a formulation, process, packaging, or distribution change?
  • Will the juice label use the word "pasteurized"? The juice questions and answers require a heat treatment for that word.
  • For a meat, poultry, or egg product, is HPP on the flow chart? Is it a critical control point, part of a prerequisite program, or used for quality or shelf life only?
  • Which critical operational parameters in FSIS Directive 5000.15 are written for this product: process pressure, hold time at pressure, time to achieve pressure, initial product temperature, treatment temperature, and decompression time?
  • What support connects those parameters to this product's pH, water activity, composition, packaging, and preservatives, and to the organism and the log reduction the hazard analysis uses?
  • If another establishment applies the pressure, how is the product controlled, and is pre-shipment review held until the record shows the critical limits were met?
  • Which package did the validation use? Ohio State states that the package may see a 15% volume reduction and that glass bottles and tin cans do not transmit the pressure.
  • For this pH and this storage temperature, what is the documented result for bacterial spores? The draft guidance and the Ohio State fact sheet state that pressure alone, at ambient or chilled conditions, does not inactivate spores.

Get the answers for this SKU from the plant that will run it. A pressure, a hold time, or a package from another food is a result for that other food.

Where this sits with NXTCPG

Choosing the plant sits in Source & produce. If the open question is which co-packer can run the SKU, and which pressure process the rule for that SKU requires, start a project. For equipment, minimums, who buys the ingredients, and who owns the formula, use how to choose a co-packer. For the thermal process in a hermetically sealed container, use what retort processing is.

Sources

FAQ

What is the HPP process?

FDA's juice hazards-and-controls guidance describes high pressure processing as a technology in which pressure, in excess of 30,000 to 45,000 psig, is the principal anti-microbial agent, and states that it has been shown to be effective in reducing vegetative pathogens. The same section states that both semi-continuous and batch processes have been developed. FDA's juice HACCP questions and answers give high pressure as an example of one control measure that has been shown to reduce the pertinent microorganism by at least 5-log. For juice covered by 21 CFR 120.24, that performance standard is a 5 log (i.e., 10⁵) reduction in the pertinent microorganism, for a period at least as long as the shelf life of the product when stored under normal and moderate abuse conditions. This answer is not a process for a particular food.

What is an HPP machine?

FDA's draft preventive-controls guidance describes a batch system: the food is packaged in a flexible or semi-flexible package, placed into a chamber, and immersed in water or some other pressurizing fluid, then held at pressure. The chamber is depressurized and the product is removed. Ohio State University Extension describes that batch operation as a sample basket loaded into a high-pressure chamber, with a pump pressurizing a fluid such as water so the pressure is transmitted through the package into the food. The fact sheet states that commercial-scale equipment is available with vessel volumes ranging from 35 to 525 liters. The draft guidance states that it is not binding. Neither document names one machine for every food. This answer is not a specification for a particular plant.

How is high pressure processing different from retort processing?

21 CFR 113.3 defines a retort as any closed vessel or other equipment used for the thermal processing of foods. FDA's juice hazards guidance discusses high pressure processing under other non-thermal treatments and states that pressure is the principal anti-microbial agent. The same guidance states that the temperature of the product does increase during high pressure processing. Ohio State University Extension states that pressure treatment at ambient or chilled temperatures does not inactivate bacterial spores, and that treated products are typically distributed under a refrigerated environment. A juice processor subject to 21 CFR Part 113 or Part 114 is exempt from the 5-log paragraph in 21 CFR 120.24(a). This answer does not decide which rule covers a SKU.

Can juice treated by high pressure be labeled pasteurized?

FDA's juice HACCP questions and answers state that pasteurization is a heat treatment sufficient to destroy pathogens, and that to be labeled as "pasteurized," a juice must be heat treated to destroy pathogens. The same questions and answers list high pressure as an example of a control measure for achieving a 5-log reduction without pasteurizing the product. Whether a validated process meets 21 CFR 120.24 is a separate question from which word the label uses. This answer is the juice guidance's labeling statement. It is not a review of a particular label.

What should a brand ask a co-packer before using HPP?

Ask which rule covers the SKU. For juice, ask whether the control measures will consistently produce at least the 5-log reduction in 21 CFR 120.24(a) for the shelf life under normal and moderate abuse conditions, whether the treatment is applied directly to the juice, and whether that reduction and final packaging occur in one facility under 21 CFR 120.24(c). Ask for the critical limits for process time and pressure, which the juice hazards guidance recommends for high pressure processing systems, and for the date of the last HACCP-plan validation under 21 CFR 120.11(b). For a meat, poultry, or egg product, ask whether HPP is on the flow chart, whether it is a critical control point, a prerequisite program, or used for quality, and which critical operational parameters in FSIS Directive 5000.15 are defined for that product. This answer is not a product-specific determination.