Non-thermal processing technologies inactivate microorganisms and extend shelf life without relying on heat. Because they avoid high temperatures, these methods tend to preserve the flavor, color, texture, and nutritional value of foods far better than conventional thermal treatments. That makes them especially relevant as consumer demand grows for minimally processed, "fresh-tasting" products.

This section covers the major non-thermal methods: pressure-based, electrical, acoustic, and electromagnetic approaches.

High Pressure Processing (HPP)

HPP subjects food to extremely high hydrostatic pressure, typically in the range of 400–600 MPa (though equipment can operate from 100–1000 MPa). At these pressures, microbial cell membranes and proteins are disrupted, inactivating vegetative bacteria, yeasts, and molds.

A few key characteristics set HPP apart:

Pressure transmits uniformly through the product, so size and shape don't matter. A thick block of guacamole receives the same treatment at its center as at its surface.
It works on both solid and liquid foods: juices, guacamole, deli meats, shellfish, and wet salads are common commercial applications.
Flavor, texture, and heat-sensitive nutrients (like vitamin C) are largely retained because no high temperatures are involved.
Shelf life extension happens without added chemical preservatives.

The main limitations are cost and packaging. HPP requires expensive equipment, and packaging must be flexible enough to transmit pressure (rigid containers like glass jars won't work). Also, bacterial spores are highly pressure-resistant, so HPP alone may not achieve commercial sterility for low-acid foods.

Pulsed Electric Field (PEF) and Cold Plasma

PEF applies short bursts of high-voltage electricity (typically 20–80 kV/cm, lasting microseconds) across a food product. The electric field causes electroporation, where pores form in microbial cell membranes. Once those pores become large or numerous enough, the cell can't recover and dies.

Best suited for liquid and semi-liquid foods like fruit juices, milk, and liquid eggs.
Treatment times are very short, so there's minimal impact on flavor, color, and nutritional content.
Less effective against bacterial spores, similar to HPP.

Cold plasma takes a different approach. An electrical discharge ionizes a gas (air, nitrogen, or helium), creating a mixture of reactive species: free radicals, ions, UV photons, and excited molecules. These reactive species attack microbial cell walls and membranes on contact.

Primarily a surface treatment, effective on fruits, vegetables, nuts, meats, and packaging materials.
Works against bacteria, molds, and even biofilms.
Has potential to replace chemical sanitizers (like chlorine washes), reducing both chemical residues and water usage.
Still relatively new at commercial scale, so process standardization is ongoing.

High Pressure Processing (HPP), Frontiers | Impact of High-Pressure Homogenization on the Extractability and Stability of ...

Ultrasound

Ultrasound uses sound waves at frequencies above 20 kHz. When these waves pass through a liquid food, they create rapidly forming and collapsing microscopic bubbles, a phenomenon called cavitation. Each bubble collapse generates intense localized heat and pressure at a tiny scale, which disrupts microbial cells and inactivates enzymes without heating the bulk product.

Often combined with mild heat (thermosonication) or pressure (manosonication) to boost microbial kill rates beyond what any single method achieves alone.
Applications go beyond safety: ultrasound accelerates brining and marination by improving mass transfer, and it can extract bioactive compounds from plant materials more efficiently.
Process parameters (frequency, power intensity, and treatment time) need to be optimized for each specific food, since the wrong settings can damage texture or create off-flavors.

Electromagnetic Spectrum Technologies

Irradiation

Food irradiation exposes products to ionizing radiation from one of three sources: gamma rays (from cobalt-60 or cesium-137), X-rays, or electron beams. The radiation damages microbial DNA, preventing organisms from reproducing. It's effective against bacteria, parasites, and insects.

Irradiation doses are measured in gray (Gy) and are regulated by category:

Low dose (up to 1 kGy): inhibits sprouting in potatoes and onions; kills insects in grain and fruit.
Medium dose (1–10 kGy): reduces pathogens like Salmonella and E. coli in meat, poultry, and spices.
High dose (10–50 kGy): sterilizes spices and certain shelf-stable products.

Irradiated food does not become radioactive. The energy passes through the product and is gone. Nutritional losses are comparable to or less than those from conventional cooking. Despite this, consumer acceptance remains a significant hurdle, largely due to the word "radiation" triggering safety concerns that aren't supported by the science. Irradiated foods must carry the radura symbol on their label in most countries.

Facilities require strict shielding and regulatory oversight, which adds to infrastructure costs.

Ultraviolet Light (UV) and Ozonation

UV light, specifically UV-C in the 200–280 nm range, inactivates microorganisms by causing thymine dimers in their DNA, which blocks replication.

Commonly used for surface decontamination of foods, packaging, and processing equipment, as well as for treating clear liquids like water and apple cider.
Effective against bacteria, viruses, and mold spores.
The main limitation is penetration: UV only works where light can reach. Surface irregularities, crevices, and turbid liquids create shadows where microbes survive. For this reason, UV is often paired with other treatments.

Ozonation uses ozone ( $O_3$ ), a powerful oxidizing agent, to destroy microorganisms by attacking their cell membranes and enzymes.

Can be applied as a gas (for storage rooms or dry products) or dissolved in water (for washing produce, seafood, or equipment).
Effective against bacteria, viruses, parasites, and even some mycotoxins.
Ozone is unstable and breaks down quickly back to $O_2$ , so it must be generated on-site, usually by passing oxygen through an electrical discharge or UV lamp.
At high concentrations, ozone can oxidize food components like lipids and pigments, causing off-flavors or color changes. Careful dose control is essential.
Because ozone leaves no chemical residue after it decomposes, it's considered more environmentally friendly than many chemical sanitizers.