Ozone as a sterilising agent

Ozone (triatomic oxygen, O3)  is in many ways ozone an ideal sterilising agent: it can be created from oxygen in air, it is a powerful germicidal agent, effective all microorganisms, including bacteria, viruses, moulds, yeasts and spores. The key benefit of ozone is that unlike other sterilising chemicals it decays back to harmless oxygen, leaving no residuals.

Ozone has a long history as a disinfecting agent, with early uses in medical sterilisation and decontamination in the late 19th century, but difficulties in handling meant that chlorine based systems have been more widely used since the 1920s.  Anacail’s unique technology creates ozone inside the final, sealed packaging of products removing the safely and handling difficulties that have restricted its use.

The in-pack ozone system

Anacail tray pack process no logo 750

The Anacail technology removes all the handling and safety barriers associated with the use of ozone by generating ozone directly in the final product packaging, after the packaging is sealed.

Ozone is produced when a localised region of ionised gas (a plasma) is generated in the pack. This is achieved by creating a well-defined region of very intense electric field from an external high-voltage electrode system. The electric field creates high energy particles which collide with and break apart oxygen molecules (O2) forming highly reactive single oxygen atoms (O*) known as radicals. When these radicals collide with another oxygen molecule, they can bond with it forming ozone (O3). The ozone thus formed will diffuse around the pack. Where it collides with surfaces it will decompose, oxidising surface contaminants and killing microorganisms. Any unreacted ozone will spontaneously decay back to oxygen over a timescale of minutes to a few hours, depending on the pack contents and temperature.

The product to be treated is first sealed into its final packaging. Many gas mixtures, including air and common modified atmosphere (MAP) compositions, are possible in the pack provided that they contain at least some oxygen. The ozone head containing the electrode system is connected tightly to the face of the pack using a vacuum system. When a good attachment is achieved, the ozone head is energised. It produces intense electric fields which penetrate the pack, generating a plasma and creating ozone within the sealed package without affecting its integrity in any way. This process is rapid, generating enough ozone within a timescale typically of 1-2 seconds and allowing relatively simple integration into standard production lines. The head is then detached from the pack and the ozone diffuses around the pack interior persisting for a period of minutes to hours, depending on the pack contents. During this time the ozone acts as a sterilising agent, as described above. After a few hours all the ozone has decayed, and the pack contains almost exactly the same gas mixture as before the treatment, but with a significant reduction in the concentration of live microorganisms.

In trials of plated microorganisms (including Pseudomonas aeruginosa, Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, Aspergillus brasiliensis, Lactobacillus Bevis and Campylobacter), reductions incontamination of 2 – 3 logs were seen, using a very brief (0.6 second) ozone treatment time. Significant shelf-life improvements have also been observed over a range of perishable foodstuffs.

Food Preservation

Anacail provides a unique technology for improving the quality and shelf-life of fresh produce. The Anacail System uses plasma technology to convert a portion of the oxygen inside a food pack into ozone, a natural germicidal agent.

The process shown above is rapid and is applied to products in their final retail packaging, making the process suitable for high-speed production lines. Ozone is a fast-acting germicide that reduces spoilage organisms and pathogens on the surface of foods, increasing shelf life. The ozone breaks down completely and returns to oxygen within minutes of the treatment.

A number of benefits were shown in extensive trials, including significantly longer shelf life and better produce quality. Other benefits range from fewer in-store losses and customer complaints, to a lower number of spoilage organisms and pathogens.

Shelf-life extension

In-pack ozone can improve the quality of food products within and beyond shelf life by reducing moulds and rots. In the example below, in-pack ozone was able to prevent moulding for 16 days in the majority of packs, 8 days longer than the control packs.
This technology has shown significant improvement for berries, tomatoes and grapes in extending shelf life and improving the quality of the products.

Grape Graph

Figure 1. Average quality of packs of red grapes over 16 days. Quality scored from 1 (perfect) to 3 (unsellable). Packs are classed as unsellable when mould is present.


Figure 2. Number of grapes with mould over the trial for control and ozone treated packs. Each row represents an individual pack. Rows have been coloured blue (no mould) to red (mould present).

Botrytis reduction

Tomato Botrytis

Tomatoes infected with Botrytis, and then treated with Anacail in-pack ozone showed no mould in the majority of samples after 6 days at room temperature. In contrast, control tomatoes showed extensive mould by this date.

Medical Device Sterilisation

Sterilsation BenchtopAnacail has developed a prototype device for medical sterilisation with a bench top footprint.

The device is self-contained in a single box and can be powered from mains electricity in a hospital or primary care setting. It is intrinsically electrically safe and the only moving parts are the hinges on the lid and user control panel.

Operation of the device is simple, and consists of placing the medical device to be sterilised into a bag or tray, sealing the bag and placing it inside the Anacail device next to the plasma head. The device is then closed, the operator pushes the ‘go’ button and the ozone is generated inside the bag to sterilise the device. The sterilised device can then be stored prior to use, by which time the ozone will have decayed back to oxygen and thereby preventing any exposure of the user to harmful gases.

Anacail will be developing this from prototype to CE marked medical device and high level decontamination protocols.