Food Industry Applications for Ozone

The key to good health is consuming a balanced diet that is rich in fresh vegetables and fruits. Consumers who adhere to this advice are maximizing their consumption of fresh produce. The food industry faces the challenging task of maintaining safety in fresh produce as this demand increases. 

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Critical outbreaks of illness can be caused by contamination with microorganisms such as bacteria and viruses, putting significant strains on public health and creating economic losses within the food industry.

Viruses are normally caught through produce that is consumed raw [1]. Research has demonstrated that melons, tomatoes, lettuces, berries, and scallions (green or spring onions) are the most probable to be linked with outbreaks of hepatitis A and norovirus. 

Alternative types of produce such as pomegranates, mangoes, pineapples, and grapes have also been named as risk factors. 

One of the challenges is that hepatitis A and norovirus can live for extended periods of time on the surface of produce; and they can also be kept in the tissues or roots of plants, which means that washing will not exclude them. 

Anxiety has also grown regarding the emergence of antimicrobial-resistant (AMR) bacterial strains in fresh produce over the past twenty years. Resistant bacteria can impact people throughout the food chain in a range of ways. 

For example, crops can be exposed to contaminated manure; fruit, shellfish, and vegetables can be exposed to contaminated water; cross contamination is found in environments with a lack of adequate hygiene practices; and meat can be contaminated with resistant bacteria originating in the animal’s stomach. [2]. 

Solving the AMR challenge comprises actions such as introducing surveillance programs, strengthening food safety systems, and developing industry, government, and public cooperation. 

Ozone as a Disinfectant

Ozone (the triatomic form of oxygen) has been utilized as a disinfectant for more than a century. It was originally employed in drinking water in 1893, in the cold storage of meats as a food preservative in 1909, and to stop the growth of mold and yeast on stored fruits in 1939 [3]. 

It destroys bacteria, viruses, fungi, protozoa, and biofilms through the process of oxidation, which means the microbes cannot become resistant. 

Multiple sectors of the food industry now employ ozone to treat, store, and process foods such as meat and poultry, from raw products up to freshly-cooked products, and products just before being packaged. Along with disinfecting food, it also extends the shelf-life of various kinds of produce [4]. 

Ozone is additionally utilized to decontaminate food storage areas and processing equipment [3]. Water that has been ozone-enriched can be sprayed on clean rooms, equipment, tanks, walls, drains, and floors. Its use stops the build-up of biofilm over time. 

Why Ozone? 

As an ecologically sound choice, ozone is a natural gas that breaks down into oxygen very rapidly [5]. It happens in the environment where it shields the Earth from dangerous radiation. 

At ground-level, ozone is a greenhouse gas that is produced when specific air pollutants have a reaction with sunlight. Ozone created through ozone generators is not harmful to the environment.

A wide-spectrum biocide, ozone is successful against the treatment of bacteria, viruses, fungi, protozoa, and biofilms [3]. Ozone is prone to reactions with alternative substances and has a strong oxidation potential (2.07 V). 

This means that it is almost twice as oxidizing as chlorine, which is a frequently used disinfection technique in the food industry. As ozone disinfects through the process of oxidation where it damages cell walls, the microbes cannot become resistant. 

In comparison with the use of alternative treatments such as chlorine, the greater kill rate means that utilizing ozone enables industry users to decrease retention times and employ smaller reaction tanks. Cost benefits can be observed by heavily decreasing investment expenses.

The use of chlorine can create possibly harmful by-products or residues, including chlorinated hydrocarbons and trihalomethanes (such as chloroform). 

The use of ozone has a further advantage in that it reverts to oxygen efficiently, so there are no challenges with disposal and any runoff water is clean, decreasing charges as a result of wastewater disposal [5].

A further important benefit is that ozone can be produced on-site in food plants and does not demand any special treatment or storage [3]. This is not the same for chlorine, which needs trained personnel to process, mix, and dispose of harsh chemicals.

How to Generate Ozone

Ozone gas is normally produced on-site due to the quick nature of its decomposition. The gas is pumped into the water and the ozonated water is utilized as a bath, spray, mist, or rinse. The ozone lasts for only several minutes before decaying into oxygen [5].

The industrial production of ozone entails either cold plasma (the dielectric barrier discharge technique) or corona discharge [6]; ultraviolet radiation can additionally be employed with air [4].

In the first technique, pure oxygen is delivered between two electrodes divided by an insulating barrier, and a plasma (partially ionized gas) is produced [6]. It includes some single atoms of oxygen, and when these mix with any oxygen molecules that remain, ozone is formed (O3). 

In the Corona discharge system, the air is directed into a corona discharge tube and placed under a strong electrical field which produces plasma and enables the formation of ozone. Corona discharge generators also produce nitrogen oxides (NOx), which will create corrosive nitric acid if in contact with water.

A key aspect of efficiency is the temperature of the feed gas as lower temperatures are optimal. Cooling water is utilized to offer control of temperature. Due to the reactive nature of ozone, only a few materials are appropriate to be used as ozone reactors. 

These are aluminum, glass, stainless steel, polytetrafluorethylene, or polyvinylidene fluoride. The major difference between each method is the arrangement and design of the high-voltage electrodes.

Primozone Ozone Generators 

Primozone offers a host of high-performance ozone generators (the GM-series) founded on its proprietary ozone technology [7]. Its patented anodized aluminum reactor utilizes an optimized version of the cold plasma technique [8]. 

This series yields the highest concentration of ozone on the market, up to 20% by weight (wt%), and the highest gas pressure (3.0 bar(g)). It is easy to use, offering precise doses through the built-in controller. 

A major benefit of the GM-series is its compact size in comparison to traditional reactors. This means that the oxygen does not have to travel far and the production of ozone is more efficient. It also helps to increase gas output pressures and produces high ozone concentrations. 

The series does not demand an enclosed air-conditioned space for the generator as the electrical reactors and power units are completely integrated into the water cooling system. 

This gives the user energy savings of up to 50% and means that temperature control is highly efficient, which is essential for the creation of ozone. The aluminum design makes the range easy to clean and maintain. 

Primozone ozone generators are produced as modular units to fulfill customer requirements. The GM-series comprises eight ozone generators of various sizes and a choice to construct a generator scaled to the customer’s needs (GM-on demand). 

A positive example is the Primozone GM48 ozone generator. With a size of only 2040 x 980 x 840 mm, it creates 2.7 kg of ozone with a concentration of 20 wt%.

References and Further Reading

[1] Foodborne viruses in fresh produce on the island of Ireland, safefood (February, 2017)
ISBN: 978-1-905767-74-8

[2] Antimicrobial resistance, Food Standards Agency (2018)
https://www.food.gov.uk/business-guidance/antimicrobial-resistance-amr 

[3] Recent Ozone Applications in Food Processing and Sanitation, Food Safety Magazine (Oct-Nov 2002)
https://www.foodsafetymagazine.com/magazine-archive1/octobernovember-2002/recent-ozone-applications-in-food-processing-and-sanitation/

[4] Zeynep B et al, (2003). Use of ozone in the food industry. LWT – Food Science and Technology. 
https://doi.org/10.1016/j.lwt.2003.10.014

[5] https://primozone.com/TECHNOLOGY/WHY-OZONE/

[6] https://primozone.com/technology/production-techniques/

[7] https://primozone.com/products/ozone-generators/

[8] https://primozone.com/technology/our-ozone-reactor/

This information has been sourced, reviewed and adapted from materials provided by Primozone.

For more information on this source, please visit Primozone.

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