Ozone: Way to Improve The Food Industry

Extending food's shelf life has always been one of the significant problems in the food industry. In recent years, ozone has been used to sanitize food surfaces due to its ability to inactivate microorganisms such as viruses, gram-positive and negative bacteria, mold, and yeast. Furthermore, the new treatment also had several advantages for the environment, making it a promising green technology for food preservation.

Conventional Food Preservation (Source: https://www.nycfoodpolicy.org/)

A Strong Oxidizing Agent

As we know, ozone (O3) is naturally found in the atmosphere. However, ozone is a very unstable gas. It has the tendency to break into dioxygen (O2) or atomic oxygen (O). In order to use it as an oxidant, ozone needs to be produced in situ at the place of use. The process requires energy that can be supplied from a high voltage electrical discharge. Using methods called corona discharge (CD), dioxygen (O2) went between two metal electrodes. As a few thousand volts are applied, a filamentary electric discharge is produced. The reaction causes the gas to be disassociated, resulting in a cold plasma. After that, the oxygen molecule split, leaving atomic oxygen (O). Finally, the atomic molecules attach with the other dioxygen to form ozone.

The Ozone Generation (Source: https://doi.org/10.3390/foods10030605)

Food Application

The application of ozone for food preservation could be either in a gas or liquid form. Sterilizing food products like fruits and vegetables can be done either by using ozone water for the washing process or storing the food in a room filled with ozone gas. Ozone preserves the food through the ability to attack the microorganism's cell membrane and cell wall by oxidizing its vital cellular component. These reactions oxidize sulfhydryl and amino acids groups or polyunsaturated fatty acids on the cell wall, causing disruption in cellular activity. Hence, the response leads to the cell's death.

Ozone (blue) Kills Bacteria (Source: https://ozonesolutions.com/blog/effect-of-ozone-on-bacteria/)

This treatment has been widely used in various food products. For example, spray-washing water is used to reduce bacterial contamination on beef. Ozonated water is also used to rinse poultry meat. A study showed that ozone treatments to some contaminated fruits with Listeria monocytogenes and E. coli have the highest reduction of those microorganisms. Moreover, it is also found that the ozone treatment in vegetables resulted in reduced microorganisms with remained appearance and unchanged properties of the components.

Compared to the other technologies, ozone is a lower-cost treatment. Ozone took less than a few seconds to kill microbes, making it almost impossible to develop a resistant strain. The treatment reduces biochemical activity in food products without affecting their nutritional and sensory properties. Likewise, the treatment left no toxic residue in food. A report also showed that ozone decreases Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) after washing treatment, introducing ozone as an ecological technology.

The Efficacy of Ozone

Despite its promising advantages, ozone has a lot of factors to be considered relative to its efficacy. Research found that microbial destruction is much faster in lower pH. The efficacy also appears to get higher as temperature decreases in aqueous ozone due to increased ozone solubility and stability. Other than that, a study found that high humidity is needed for ozone gas. Below 50% of humidity level, the ozone gas loses its antibacterial activity. The presence of organic matter also played a role as it accelerated ozone decomposition, hence reducing the microorganism consumption of ozone.

It is also important to monitor the ozone concentration. The efficiency of ozone regarding concentration is described in the CT (concentration-time) concept. Most cases show that a low concentration of ozone combined with a high treatment time has the same efficacy as a high concentration on lower treatment time for the same CT value. However, in certain situations, a high concentration in a short time was found to be phytotoxic. In addition, food product's surfaces also highly contributed to ozone effectiveness. The more complex a food product's surface, the harder the microbial inactivation process.

Increasing consumer awareness has raised the demand for new safety technology for food. All these advantages make ozone the prominent technology for food preservation. Nevertheless, the treatment also has many factors which determine its effectiveness in extending food shelf life. Therefore, more study and research are needed to discover the best application for the maximum result for food products.

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References:

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Chakka, A., Sriraksha, M. and Ravishankar, C., 2021. Sustainability of emerging green non-thermal technologies in the food industry with food safety perspective: A review. LWT, [online] 151(2021), p.112140. Available at: <https://www.sciencedirect.com/science/article/pii/S0023643821012937> [Accessed 23 July 2021].

Massoud, R., Sadat Mir Mohammad Makki, F., Bahramizadeh, P., Fallahzad, S., Kohestani, S. and Armita Massoud, A., 2020. Ozone Technology in Food preservation. In: 5th international conference on applied research in science and engineering. Amsterdam: The London Engineering and Technology Society, pp.1-6.

Ozone Solutions. 2020. Effect of Ozone on Bacteria. [online] Available at: <https://ozonesolutions.com/blog/effect-of-ozone-on-bacteria/> [Accessed 26 July 2021].

Sarron, E., Gadonna-Widehem, P. and Aussenac, T., 2021. Ozone Treatments for Preserving Fresh Vegetables Quality: A Critical Review. Foods, [online] 10(3), p.605. Available at: <https://www.mdpi.com/2304-8158/10/3/605> [Accessed 21 July 2021].