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Ozone makes an impact

26 May 2020

Henrik Steffens outlines the advantages of ozone as a disinfection solution for the food and beverage sectors. 

Hygiene and disinfection of all food-contact surfaces and equipment is paramount. The first choice of disinfectant is usually sodium hypochlorite (bleach – an oxidizing biocide that is readily available and well understood. However, its very ubiquity has led to concerns that some pathogenic bacteria, such as Aeromonas and Bacillus cereus are showing signs of resistance. While there are alternative biocides available most are less easy to handle than sodium hypochlorite and may raise health and safety concerns. There is one alternative that has been around for many years but, until recently, has been little used in the food processing industry: ozone.

Food and beverage facilities typically use chlorinated water not only for automatic cleaning-in-place (CIP) procedures but for manually washing down working surfaces, conveyors and other items of equipment which are not covered by CIP. Ozone has proved a superior disinfectant in both of these applications. It dissolves in water forming a free hydroxyl radical which is a powerful antimicrobial agent. A study by Kim et al (1) showed the effect of dissolved ozone in a batch reactor on Listeria monocytogenes. Dissolved ozone at 0.4 and 0.8mg/l inactivated 4.6 and 5.7 log CFU/ml within 30 seconds. A later study (2) demonstrated that higher dissolved ozone concentrations gave faster (immediate) inactivation of the bacterium – much quicker than bleach. Ozone is also very effective at removing biofilms by rapidly oxidizing the extracellular polysaccharides that give biofilms their adherent nature. A major benefit of ozone for the food industry is that it decomposes rapidly to form oxygen, leaving no residues.

A portable solution
Traditionally, ozone generators have been large and costly, fixed items in the process plant with health and safety issues. This is no longer the case. Evoqua, for example, can offer a small, portable system – the PC Series disinfection system – which can provide ozonated water instantly anywhere in the food processing factory simply by connecting it to a water supply. 

The all stainless-steel disinfection system incorporates an on-board oil free air compressor which delivers air to an oxygen concentrator. This passes through an air-cooled ozone reactor with adjustable output. The ozone gas is then injected and dissolved into the flow of water delivered by an integral booster pump to a connected hose and nozzle system. It also includes an off-gas destructor to ensure that no ozone gas is discharged into the workplace. 

A recent incident involving listeria at a large food processing facility in Europe resulted in an emergency telephone call to Evoqua which was able to deliver one of its PC Series disinfection systems. Before the customer started using the mobile ozone system, they used chemicals for sanitisation, but couldn’t deactivate the bacteria. Since the introduction of ozone no listeria has been detected. The use of ozone has made the products safer, enhanced the shelf-life for the fresh produce and protects the company’s brand, it has also proven to be more economical than the use of chemicals. Employees also gained a safer working environment as the ozone removed slippery biofilm from the floor, and they noticed reduced smells in the factory. 

This experience is supported by studies undertaken by the Norwegian Institute of Water Research (NIVA). They grew biofilms of Listeria monocytogenes on plastic and steel surfaces in the laboratory. The surfaces were then exposed to ozonated water, either by immersion or by flushing. After treatment with ozonated water, no viable bacteria were found. 

1.Kim J G et al – Application of ozone for enhancing the microbiological safety and quality of foods: a review J Food Prod. 1999 Sep;62(9):1071-87.
2.Kim J G, Yousef AE – Inactivation kinetics of foodborne spoilage and pathogenic bacteria by ozone. J Food Sci 2000 65:521-528.

Henrik Steffens is sales manager at Evoqua.

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