Unlocking the Power of High Pressure Processing (HPP):

The Need for Process Validation

Reviewed and Approved by Ben Howard, Laboratory Director, Food Safety Net Services

1-Minute Summary

  • High Pressure Processing (HPP) is a non-thermal pasteurization technique that preserves food nutrition and taste.
  • HPP extends shelf life by inactivating spoilage microorganisms and pathogens.
  • Regulatory compliance is essential, with FDA and USDA setting specific requirements for HPP use.
  • Process validation for HPP involves three stages: Process Design, Process Qualification, and Continued Process Verification.
  • Competent processing authorities are crucial for conducting and ensuring compliant and safe HPP processing.

High pressure processing (HPP) has grown in popularity as some consumers continue to favor “minimally processed” foods and beverages. People are placing a premium on food products that eschew traditional thermal processing for other methods of pasteurization that help preserve taste, texture, and nutrition.

It is important to remember that as novel technologies for food and beverage processing emerge, these processes must meet regulatory requirements for safety. This is where high pressure processing enters the discussion. While HPP can help you create food products that satisfy consumer preferences, it's crucial to substantiate its effectiveness with scientific evidence to comply with regulatory mandates.

In this post, we’ll cover the basics of high pressure processing and explain what you need to know about validating HPP processing to verify safety.

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The Essentials of High Pressure Processing (HPP)

First, let’s define our terms. High-pressure processing (HPP) is a non-thermal, cold pasteurization technique.

In this method, products sealed in their final package are subjected to extremely high levels of hydrostatic pressure (300-600 MPa; 43,000-87,000 psi), transmitted uniformly and instantly through water.

Proponents of the technology list several potential benefits:

Nutritional Preservation

Unlike thermal methods, which expose products to high temperatures, HPP operates at ambient or even cooler temperatures. Heat can degrade certain nutrients, particularly heat-sensitive vitamins like vitamin C and some B vitamins. When it comes to high-pressure processing for juice, for instance, the product retains more of its vitamin and mineral content than it would through heat pasteurization.

Moreover, enzymes, which are often beneficial and contribute to the natural flavor of food, are more likely to retain their activity through HPP processing than through heat treatments. Protein structure, another key nutritional element, is also more likely to remain intact or undergo less denaturation during HPP, preserving the amino acid profile of the food.

Shelf-Life Enhancement

HPP processing extends the shelf life of food and beverage products by inactivating spoilage microorganisms. This is achieved through the application of pressure as high as 87,000 psi, which disrupts the cellular membranes of these microorganisms, halting their metabolic processes and preventing their reproduction.

By effectively suppressing these spoilage microorganisms, high pressure processing can reduce the rate of product degradation, thereby extending the product's shelf life.

Enhanced Safety

High pressure processing has been demonstrated to be effective in the inactivation of pathogenic bacteria, viruses, yeasts, molds, and parasites across many high-moisture food and beverage categories. The ultra-high pressure disrupts the biochemistry of these microorganisms, preventing them from causing foodborne illnesses.

This is of paramount importance when it comes to high-risk or ready-to-eat products such as minimally processed juices, salads, sandwiches, and seafood, which are often consumed without any further kill step.

Moreover, unlike chemical preservatives or treatments, HPP does not leave any residue or alter the food's natural composition, maintaining its characteristics.

How Does High Pressure Processing Work?

The process begins by placing the packaged food or beverage product in a high-pressure chamber filled with water. After sealing the chamber, pressure as high as 87,000 psi is applied uniformly from all sides for a certain duration.

This pressure disrupts the cellular activity of many types of vegetative foodborne microorganisms, effectively neutralizing them. It is essentially a form of high-pressure pasteurization, eliminating bacteria and other pathogens without the need for high heat.

The Regulatory Landscape: Process Validation and Compliance

So, how do you know if your HPP process achieves the desired result of pathogen reduction, shelf-life extension, and product safety? By validating the process.

Process validation involves the collection and evaluation of data, starting from the process design stage through commercial production. This evidence-based approach establishes the assurance that a process can consistently yield a product of the desired quality.

Let’s take a closer look at process validation for HPP.

Compliance with Regulatory Standards

It all starts with regulatory compliance.

The Food and Drug Administration (FDA) and the United States Department of Agriculture (USDA) have established specific requirements for the use of HPP in the food and beverage industry.

  • FDA regulates high pressure processing under the Food Safety Modernization Act (FSMA).
    • According to FSMA’s rule on preventive controls for human food (21 CFR Part 117), food manufacturers are required to develop and implement a food safety plan that effectively controls any potential hazards. This includes microbiological hazards that can be controlled through HPP. The food safety plan must also include validation that the preventive controls are effective in reducing the hazards to an acceptable level.
    • For the juice industry specifically, FDA requires adherence to the Juice HACCP regulation (21 CFR Part 120), which outlines the steps manufacturers must take to mitigate potential hazards, including those that can be controlled through HPP.
  • USDA, which regulates meat, poultry, and egg products, requires establishments to validate and verify their HACCP plan per 9 CFR 417.4. If high pressure processing is used, you must validate with scientific support that the application of HPP at a specified level will consistently achieve the desired effect, for example, a 5-log reduction of a specified pathogen.

These regulations underscore the need for food and beverage processors to scientifically validate their HPP process as part of their regulatory compliance efforts.

Quality Assurance

Process validation acts as a proactive measure to assure the quality and safety of food products. It substantiates that your process consistently yields results that adhere to predefined specifications and quality attributes, helping support your QA team.

A validated process also assures consumers of the safety and quality of your products, a key selling point in today's health-conscious market.


The FDA Stance on Process Validation for HPP

FDA has delineated clear guidelines on process validation, particularly for high pressure processing. The Agency recognizes HPP as a kill step – a process in production that reduces or eliminates harmful microorganisms to safe levels.

As per FDA guidelines, the food product manufacturer must scientifically validate the efficacy of the HPP process to achieve its intended effect. In the case of its use as a direct intervention against pathogens, it must prove to be effective in the inactivation of the most pressure-resistant strains.

Process validation comprises three stages:

Three steps of process validation for high pressure processing, including design, qualification, and verification.

1) Process Design

Process Design is the first critical stage of process validation.

During this phase, food and beverage processors need to develop a deep understanding of HPP technology, its possibilities, and its limitations. The goal is to design a process that will reliably achieve the desired results, which is typically a significant reduction of harmful microorganisms without compromising the product's quality, texture, and nutritional value.

In this stage, producers must identify the product's specific attributes and the targeted microorganisms, considering the product's pH, water activity, consistency, and other factors. Additionally, it's crucial to understand the resistance of these microorganisms to high pressure and at what level of pressure and duration they are effectively inactivated.

Producers must also consider the type of packaging used since not all materials can withstand high-pressure conditions. These factors will guide the design of the HPP process to ensure it can meet the safety and quality requirements.

2) Process Qualification

Once a process is designed, the next stage of validation begins: Process Qualification.

The objective of this stage is to evaluate the designed process to ascertain whether it can deliver consistent results when operated at a commercial scale.

During this phase, rigorous testing should be carried out to confirm that the HPP process, as designed, can achieve the desired log reduction of microorganisms for each specific product. This usually involves product inoculations and microbiology testing of trial samples before and after the HPP treatment.

In addition, the equipment itself should be qualified to ensure it is capable of delivering the required pressure and maintaining it for the desired duration.

3) Continued Process Verification

Continued Process Verification is the third and ongoing stage of process validation. This phase ensures that the HPP process remains effective and in a state of control during routine production.

This stage involves regularly monitoring the process parameters (pressure, time, temperature) and routine testing of product samples to ensure the continued effectiveness of the process. If any significant deviations from the process parameters are noted, corrective actions should be taken and their effectiveness confirmed.

The information collected during this phase should be used for regular reviews of the process and for making any necessary adjustments to ensure continued process control.

Keep in mind that any changes to the product formulation, packaging material, or HPP process parameters could potentially affect the effectiveness of the process and may require re-validation.

The Importance of Process Validation by a Competent Processing Authority

Given the complexities and specifics of high pressure processing, a competent and experienced processing authority should conduct the process validation.

These experts are well-versed in HPP technology, understand its nuances, and can ensure that the process is compliant with FDA and USDA regulations, reinforcing the credibility and safety of your operations.

The scientists at FSNS Lab+, the contract research division of Certified Laboratories and Food Safety Net Services (FSNS), have performed hundreds of process validations for HPP for a variety of industries, including minimally processed juice, ready-to-eat foods, low-acid canned foods, and more. In fact, we have worked with the top manufacturers of high pressure processing equipment to validate equipment effectiveness, adding to our expertise.

Contact us with questions or to get a quote for your next HPP process validation.

Topics: Food & Beverage