Prepared by: Dr. Nurul Izzah Khalid

Senior Lecturer

Department of Food Technology, Faculty of Food Science and Technology, UPM

Figure 1. Cleaning and disinfection of high-pressure processing equipment using an automated cleaning-in-place system.

High-pressure processing (HPP) is a food preservation method that uses very high water pressure instead of intense heat. Packaged food is placed inside a pressure vessel filled with water and treated at approximately 300–600 MPa. The pressure can reduce many harmful and spoilage-causing microorganisms while helping the food retain its fresh taste, colour, texture, and nutrients. However, some bacterial spores and food enzymes may survive, so many HPP foods must still be kept refrigerated (Houška et al., 2022).

Why Must HPP Equipment Be Clean?

Food is normally treated inside sealed packaging and does not directly touch the machine. However, a package may sometimes leak or burst during processing. Food may then enter the pressure vessel, trays, pipes, filters, conveyors, and water system.

If the residue is not removed quickly, it may dry, become difficult to clean, and support microbial growth. Regular cleaning also protects the machine and helps it operate safely and correctly (Hiperbaric, S.A., n.d.).

Possible Hazards

Poorly cleaned equipment may create three main hazards.

• Physical hazards include broken packaging, plastic pieces, loose machine parts, hair, and other foreign materials.
• Chemical hazards may result from using too much detergent or sanitiser, failing to rinse properly, or using chemicals that are unsuitable for the equipment.
• Biological hazards may occur when food residues remain in wet areas such as pipes, filters, drains, tanks, and conveyors. Microorganisms may grow and form biofilms, which are sticky layers that are more difficult to remove.

How Is the Equipment Cleaned?

The Hiperbaric 55 requires both manual cleaning and an automatic cleaning cycle.

Manual cleaning is used for accessible areas such as the machine covering, trays, conveyors, and surrounding floor. The internal pipes are cleaned using the machine’s automatic cleaning cycle (Hiperbaric, S.A., n.d.).

A simple cleaning procedure involves five steps:

1. Remove residues. Remove spilled food, broken packaging, and visible dirt before they dry.
2. Wash the equipment. Apply an approved alkaline cleaning solution to remove fats, proteins, and other food deposits.
3. Rinse thoroughly. Use plenty of water to remove loosened dirt and cleaning chemicals.
4. Apply a sanitiser. The Hiperbaric 55 manual recommends peracetic acid-based sanitisers. Acetic acid, peracetic acid, and hydrogen peroxide are also listed as permitted chemicals for cleaning or disinfection.
5. Rinse and dry where required. Sensitive areas, particularly the high-pressure seal area, should be dried carefully.

Cleaning and sanitising have different purposes. Cleaning removes food, grease, and dirt, while sanitising reduces microorganisms on a surface that has already been cleaned (U.S. Food and Drug Administration [FDA], 2022).

Important Safety Precautions

Operators should avoid spraying water directly onto electrical cabinets, control screens, motors, and sensors. High-pressure water, steam, and rough brushes should not be used on sensitive parts because they may damage seals, plugs, or the pressure vessel.

Only approved chemicals should be used. The Hiperbaric 55 manual states that the cleaning-agent concentration should not exceed 0.7%, while the sanitiser concentration should not exceed 0.2% (Hiperbaric, S.A., n.d.).

What Happens When a Package Bursts?

When a package leaks or bursts, the operator should:

• remove the damaged package and packaging fragments;
• remove food residues before they dry;
• clean the pressure vessel, trays, pipes, and water filters;
• inspect the conveyors, tanks, and drains; and
• check that the machine is clean before restarting production.

The affected parts should be cleaned as soon as possible after the incident (Hiperbaric, S.A., n.d.).

How Is Cleanliness Checked?

Operators should first inspect the machine for visible food, packaging pieces, detergent residue, standing water, and damaged parts. Equipment surfaces should be clean to sight and touch before sanitising and before production begins (FDA, 2022).

The Hiperbaric manual also recommends swab testing every two weeks after sanitation and before production. Areas such as the vessel, conveyor cover, drain, water tanks, pipes, filters, and processing baskets may be tested. ATP testing and processing-water sampling may also be used to check cleanliness (Hiperbaric, S.A., n.d.).

Conclusion

HPP can help make food safer and extend refrigerated shelf life without intense heating. However, safe processing still depends on good packaging, refrigeration, correct machine operation, and proper cleaning.

Food residues should be removed quickly, approved cleaning chemicals should be used correctly, and cleanliness should be checked before production. Following the Hiperbaric 55 operation manual helps protect both the equipment and the food being processed.

References

1. Hiperbaric, S.A. (n.d.). HPP equipment operation manual: Hiperbaric 55 (Rev. 00) [Operation and maintenance manual].
2. Houška, M., Silva, F. V. M., Evelyn, Buckow, R., Terefe, N. S., & Tonello, C. (2022). High pressure processing applications in plant foods. Foods, 11(2), Article 223.
3. S. Food and Drug Administration. (2022). Food Code 2022. U.S. Department of Health and Human Services.

Date of Input: 05/08/2026 | Updated: 05/08/2026 | nurulizzah