Plasma: an alternative to chlorine disinfection
Teagasc researchers are exploring the use of novel plasma technology in the cleaning of food contact surfaces.
When microorganisms stick to food processing surfaces that haven’t been properly sanitised, they can contaminate food products they come into contact with. They then form biofilms (one or more types of microorganisms that can grow on many different surfaces) that pose a major global challenge in the fight against product contamination.
As sources of contamination in food processing and drinking-water distribution systems, biofilms can be damaging to our health. The need to create effective techniques to counter biofilm infections presents one of the most pressing challenges in antibacterial research, as evidence indicates biofilm is becoming increasingly resistant to standard decontamination methods, such as chlorine and detergents, and antibiotics.
The World Health Organization has identified antimicrobial resistance as one of the greatest threats to human health. It has endorsed a global action plan for tackling this challenge, which includes encouraging research and development of new antimicrobial agents. To support this action, Teagasc has launched PASTE – a project exploring the use of novel technology, such as plasma, as an alternative to antimicrobial resistant disinfectants.
Chlorine disinfection in the food industry
Chlorine and chlorine-based disinfectants are the most commonly used chemical disinfectants in the food industry for microbial inactivation on food contact surfaces, due to chlorine’s strong oxidising and disinfecting ability.
One issue with this method, however, is the entry of chlorine residues, such as chlorates, into the food supply chain. This occurs through the use of chlorinated water and through residual chlorine present in processing equipment. Clean-in-place procedures – used to automatically clean the inside of equipment such as pipes and filters – typically use chlorine-based sanitisers, both at processor and farm level, and are often responsible for this.
The presence of chlorates in food products has become a major food safety issue in the EU, as they are known to cause toxicological effects by inhibiting iodine uptake in humans – a mineral that helps our bodies to make thyroid hormones. A default maximum residual limit for chlorate of 0.01mg/kg is applicable for all foods, meaning a safer alternative is needed.
Plasma as an antimicrobial agent
Plasma – an ionised gas – has rapidly evolved as a technology for biological applications such as microbial decontamination, wound healing and cancer treatment. It has cytotoxic effects, which means it can damage cells or cause them to die.
The PASTE project team used plasma-activated water (PAW) – plasma treated with water – to conduct experiments, assessing its efficacy in disinfecting bacterial biofilms on food contact surfaces. The initial trials demonstrated the efficacy of PAW against key food spoilage microorganisms, reducing their presence by between 50% to 85% following a 15-minute treatment.
The project team is also investigating the effect of this PAW on chemical and structural changes on the biofilm matrix (mostly carbohydrates, proteins, lipids and extracellular DNA).
A promising technology
Given the unique species associated with such highly non-equilibrium plasmas, the approach suggests a breakthrough alternative to the use of chlorine for the cleaning of spray dryers, which would be effective against spore-forming bacteria and biofilms in food processing environments. It would also be environmentally friendly, quick to come into effect and result in no toxic residues.
The PAW will be used for the cleaning of the spray dryers in the dairy industry to check the efficacy of plasma to reduce the microbial load or contamination in the final products. Comparatively, after the application of chlorine for disinfection of the food contact surfaces, the dairy products will be checked for chlorate residues.
The possibility of novel technology such as plasma as a sanitiser for cleaning-in-place procedures on spray dryers and hot plate exchangers in the dairy industry can help to guarantee product safety and quality of dairy powder, which includes infant milk powder.
The PASTE project, therefore, is offering a revolutionary new approach and potentially ‘green’ solution to how we can reduce our dependence on synthetic chemicals and their associated environmental impacts. Such a change would not only benefit human health, but also contribute towards a more sustainable future for the agri-food industry.
Food-borne pathogens that cause food safety outbreaks such as Salmonella, Escherichia coli and Listeria can be found in fruit juices, fresh produce and meat products.
This project is funded by Enterprise Ireland’s Career-FIT: Career Development Fellowship in the National Technology Centre Programme (co-funded by Marie Skłodowska-Curie Actions).
Bhavya Mysore Lokesh
Marie Slodowska-Curie Career-Fit
PLUS FellowFood Chemistry and Technology Department, Teagasc Food Research Centre, Ashtown, Dublin.
R&D Microbiologist, Nuwave Sensor Technology Ltd, Dublin.
CEO Moorepark Technology Limited, Moorepark, Co. Cork.
Principal Research Officer Teagasc Food Research Centre, Ashtown, Dublin.