A chemical-free decontamination system for fruit and vegetables

Globally, we are witnessing an increase in the number of outbreaks of food-borne illness associated with ready-to-eat fruit and vegetables. The treatments currently used, including chlorine washing, often leave a chemical residue and waste water. There is growing demand to reduce the amount of chemicals used in the process, and this can be achieved through the effective yet environmentally-friendly decontamination system currently being developed by SAFEBAG.

With funding from the FP7 programme, the SAFEBAG team is developing a novel in-pack decontamination system that will enable us to reduce the amount of chemicals used in washing. The system is based on a cold atmospheric plasma, generated inside a sealed package containing the food, which produces highly charged particles (free radicals) to damage or destroy bacteria. Preliminary research has already indicated that this in-pack non-thermal plasma (an energetic ionised gas) can significantly reduce the microbial load of fresh fruits and vegetables.

SAFEBAG is now advancing this knowledge by carrying out further research to maximise potential benefits of this technology. The plasma-based pre-competitive prototype has been built by the team and is ready to be tested by the industry in terms of effectiveness in decontaminating fresh bagged fruits and vegetables.

As the project enters this crucial testing phase, Dr. Edurne Gaston Estanga, Group Leader of Food Technologies at IRIS in Spain and Project Coordinator of SAFEBAG, speaks with research*eu magazine about the innovative elements of the technology and the way forward after industry approval.

What are the main objectives of the project?

The overall objective of the project is to develop a pre-competitive prototype of a novel process to reduce microbial load in packed fresh-cuts, based on cold atmospheric plasma technology. Such a process will ensure food safety and extend the shelf-life of the produce without altering its quality or nutritional profiles.

To achieve this goal, five objectives were set. Firstly, we aimed to use a lab scale plasma test-rig to optimise the plasma process parameters that lead to maximum antimicrobial efficacy while retaining product quality and nutrition. Our second objective was to characterise the physical plasma discharge and to correlate it with antimicrobial efficacy, in order to better understand the insides of the process. Thirdly, we aimed to scale up the process to pre-competitive level, i.e. to design and build an industrial prototype unit. Our final two objectives were to validate the performance of the prototype unit in the fresh-cut industry and to demonstrate the viability of the prototype unit.

Why is the improvement of decontamination solutions for vegetables so important?

Chlorine is one of the most effective sanitisers and its use is widespread in the fresh-cut industry. Despite strict safety & hygiene standards during processing, outbreaks of foodborne illness associated with ready-to-eat fruit and vegetables exist globally. New risks are often encountered because of changing characteristics of relevant microorganisms and the environment. Increasing the safety of these products is of paramount importance for protecting consumers, especially in view of the growth in the consumption of packaged fresh-cut produce.

What is new or innovative about the project’s approach to such decontamination?

The use of cold atmospheric plasma for food preservation purposes is an innovation in itself, and this technology has recently been added to the list of non-thermal processes for foods. Moreover, the novelty of the SAFEBAG approach lies in generating the plasma inside a sealed package containing the produce, which facilitates rapid treatment and eliminates the risk of post-process contamination. SAFEBAG is a dry, non-thermal and chemical-free washing technology, compatible with online production and MAP packaging, which leaves no hazardous residues in the treated produce.

How does plasma decontamination work exactly?

Plasma (also known as the fourth state of matter) is electrically energised gas whereby constituent molecules of the gas split to yield free electrons, radicals, positive and negative ions, quanta of electromagnetic radiation, while some molecules may still remain neutral. There are several types of plasmas depending on the conditions in which they are generated. SAFEBAG uses cold atmospheric (i.e. at near room temperature) plasma with a dielectric barrier discharge approach. The food package is treated between two high voltage electrodes. The high-voltage process ionises the gas within the electric field, including the gas contained within the package. It is this mix of active species which results in the anti-microbial effect. Reactive species interact with the food surface by altering the cell surface structure. This leads to release of cell components, thus affecting cell integrity. DNA damage can also occur depending on the type of bacteria. Crucially the active gas reverts back to stability shortly after, meaning no residual chemicals are left on the product.

Your aim is to increase shelf life while maintaining the product’s nutritional value. How successful is the project in this regard?

Laboratory work has shown promising results for a range of fresh fruits and vegetables, including spinach, cherry tomatoes and strawberries, with significant extensions of shelf-life and retention of key quality parameters, whereas certain produce has shown less favourable results (e.g. leafy greens). Given the diversity of food products found in the industry, there is no universal approach with regards to food processing.

What are the next steps for the project, and after its end?

The pre-competitive prototype has been built and is ready for industrial validation, which involves testing the technology for a wide range of industrial products and conditions. The validation trials will take place at the project partner sites, Nature’s Best in Ireland and Verdifresh in Spain. The control of the technology under industrial-like conditions is key to the successful adoption of the technology. Additional steps will be geared towards implementing the further development and scale-up recommendations resulting from industry validation trials.

When do you expect the system to be commercialised?

It is still too early to predict this. There has been significant interest from processors around the world. Testing of the prototype under industrial conditions needs to be completed, followed by a next generation technology aimed at commercial level processing conditions. It is envisaged that this could be completed in 2–3 years.