High-Pressure Processing (HPP) in Food Preservation | Principle, Equipment, Uses & Applications

Summary

High-Pressure Processing (HPP) is an advanced food preservation technique that applies pressure to inactivate microorganisms and alter food properties, improving safety and shelf life. With pressure ranges from 40 to 1000 MPa and varying temperatures, HPP is effective for a range of food products, including juices, jams, and meats. This method offers benefits like pathogen elimination, clean-label foods, and innovative product development. By using uniform pressure and controlled processing parameters, HPP helps create safer, high-quality foods without compromising nutritional value or taste.

Takeaways

• 😀 High-Pressure Processing (HPP) is a food preservation technology that applies pressures between 40 and 1000 MPa to inactivate microorganisms and alter food characteristics.
• 😀 HPP operates under controlled temperatures ranging from below 0°C to above 100°C, with treatment durations from milliseconds to several minutes.
• 😀 The Le Chatelier principle governs HPP, where applying pressure to a system results in a decrease in volume, leading to microbial inactivation and changes in food properties.
• 😀 Isostatic processing ensures that food compressed under uniform pressure returns to its original shape once the pressure is released.
• 😀 HPP equipment includes high-pressure vessels, a pressurizing system, heating and cooling systems, and data generation systems, with two main compression setups: direct and indirect compression.
• 😀 The sensitivity of microorganisms to HPP varies by type (e.g., Gram-positive vs. Gram-negative bacteria) and form (vegetative vs. spore). Spores are more resistant to high pressure than vegetative cells.
• 😀 Processing conditions for microorganism inactivation: vegetative bacteria are inactivated at 400–600 MPa, while bacterial spores require more than 1000 MPa.
• 😀 HPP food products are sealed in flexible containers and treated by applying pressure via a pressure-transmitting fluid in a chamber. Post-treatment, food is stored properly.
• 😀 Operational costs of HPP depend on exposure time, processing temperature, and pressure, with the process optimized for specific microbial targets and food characteristics.
• 😀 HPP applications include pathogen elimination, shelf-life extension, production of innovative fresh products, and clean-label formulations, enabling safer, higher-quality foods.
• 😀 Examples of HPP-treated foods include jams, fruit juices, tropical fruits, beef, and rice cakes, with varied pressure and temperature settings tailored to each food type.

Q & A

What is High-Pressure Processing (HPP) and how does it work?

High-Pressure Processing (HPP) is a food preservation technology that uses high pressure, ranging from 40 to 1000 MPa, to inactivate microorganisms and alter food attributes. The pressure is applied to the food for a specified duration, under controlled temperatures, to achieve microbial inactivation and desired food characteristics. The process is based on the Le Chatelier principle, where pressure causes a decrease in volume, which affects microorganisms, enzymes, and biochemical processes.

What are the main types of compression setups used in HPP?

There are two main types of compression setups used in High-Pressure Processing: direct compression HPP and indirect compression HPP. Direct compression uses a small diameter piston moved by hydraulic pressure, which allows fast compression and is mainly used in laboratory or pilot systems. Indirect compression uses a high-pressure intensifier to pump pressure from a reservoir into a closed high-pressure vessel, which is mainly used in commercial-scale operations.

How does HPP affect microorganisms?

HPP inactivates microorganisms by applying high pressure, which disrupts their cellular structure and metabolism. The sensitivity of microorganisms to HPP depends on the type (pathogenic or spoilage bacteria), form (vegetative or spore), and the pressure applied. Gram-positive bacteria are generally more resistant to HPP than Gram-negative bacteria, and bacterial spores are more resistant than vegetative cells due to protective compounds like calcium-rich dipicolinic acid.

What are the typical pressure conditions required for the inactivation of various microorganisms in HPP?

The pressure conditions for microorganism inactivation vary by type: vegetative bacteria are inactivated at 400-600 MPa, while bacterial spores require more than 1000 MPa. For example, Staphylococcus is inactivated at more than 500 MPa for 60 minutes, while Escherichia coli shows a 6-log reduction at 405 MPa for 10 minutes.

What materials are recommended for food packaging during HPP?

The food product is typically packaged in flexible containers such as plastic pouches or bottles. Materials like ethylene-vinyl alcohol copolymer (EVOH) and polyvinyl alcohol (PVOH) are recommended for food packaging in HPP due to their ability to withstand high pressure.

How does temperature impact the effectiveness of HPP?

The processing temperature in HPP is selected based on the treatment objective. Low-temperature HPP (HP-LT) is used for inactivating vegetative pathogenic bacteria, while HP-assisted pasteurization and sterilization are used for sterilizing low-acid foods and inactivating bacterial spores. The temperature affects both the microbial inactivation and the quality of the food product.

What are the two operation modes of HPP?

HPP can be performed in two main operation modes: batch processing and semi-continuous processing. Batch processing involves prepacked foods being loaded into a processing vessel, whereas semi-continuous processing involves pumpable products. Industrial HPP is most commonly carried out in batch processing mode.

What are some of the benefits of using HPP in food processing?

HPP offers several benefits, including pathogen elimination, shelf-life extension, and the development of innovative fresh products. It also allows for the creation of low-sodium, clean-label products without preservatives or additives, and it can improve convenience by providing ready-to-eat foods with minimal processing.

Can you provide examples of foods processed using HPP?

Examples of foods processed with HPP include jams, fruit sauces, and yogurts, processed at 400 MPa for 20ºC for 10-30 minutes; grapefruit juice, processed at 120-400 MPa for 2-20 minutes at 20ºC; and beef, processed at 100-250 MPa for 30 minutes to several hours. Other examples include tropical fruits processed at 50-200 MPa, rice cakes at 400 MPa, and more.

What factors influence the cost of HPP operations?

The cost of HPP operations depends on several factors, including the time of exposure, processing temperature, and processing pressure. The range of processing pressure varies with water activity and the type of food product being processed, making these parameters essential for optimizing cost and effectiveness.