Plasma-activated water as a sustainable intervention for reducing foodborne pathogens on fresh produce

Kaidi Wang

Fresh fruits and vegetables are an essential component of a healthy diet, but they are also increasingly associated with foodborne illness outbreaks caused by pathogens such as Salmonella spp., Listeria monocytogenes, and pathogenic Escherichia coli (1). Fresh produce is often consumed raw or minimally processed, making effective decontamination strategies critical for protecting public health. Current sanitation practices primarily rely on chemical sanitizers such as chlorine and peroxyacetic acid (2); however, these treatments may have reduced effectiveness in the presence of organic matter and are associated with concerns regarding chemical residues and environmental sustainability.

Plasma-activated water (PAW) is an emerging non-thermal technology that generates reactive oxygen and nitrogen species in water, providing antimicrobial activity against a wide range of foodborne pathogens (3). Notably, PAW is residue-free, relatively easy to generate, and does not compromise the sensory attributes of treated food products (4). While PAW has shown promising results in laboratory studies, limited information is available regarding its effectiveness on fresh produce commodities relevant to the Canadian produce industry.

The proposed project will evaluate the efficacy of PAW for reducing two major foodborne pathogens of concern to the produce industry, Salmonella enterica and Listeria monocytogenes on representative fresh produce commodities, including romaine lettuce, tomatoes, and cucumbers. Treatment performance will be compared with conventional chlorine washing practices currently used by industry, and the impact of PAW treatment on produce quality will also be assessed. The project aligns directly with CPMA’s commitment to advancing food safety and supporting practical, science-based solutions for Canadian produce growers, packers, and processors. As the produce industry seeks effective and sustainable alternatives to traditional chemical sanitizers, there is a need for Canadian-generated data demonstrating both microbial safety and product quality outcomes. CPMA funding support will enable the generation of this critical information, providing members with evidence-based guidance for evaluating PAW as a produce sanitation intervention and supporting its potential adoption within the Canadian fresh produce industry.

Recovery of dormant bacteria in biofilms encountered in fresh processing facilities and control by an environmental sanitizer based on hydroxyl-radicals

Keith Warriner

The primary objective of the research is to increase the reliability of environmental testing to recover dormant Listeria spp to facilitate mapping in root cause analysis investigations. A secondary objective will be to evaluate a hydroxyl-radical process for decontaminating environmental surfaces and drains.

Importance to CPMA: Environmental Listeria monitoring programs are a central feature of regulations under the modernization act and are a requirement by many retails under supplier verification programs. The main challenge with Listeria testing is the sporadic recovery of the bacterium even following revised sanitation plans. One cause is that Listeria can enter a dormant state that results in false-negative results when screening thereby restricting root-cause-analysis investigations and developing plans to eradication. Listeria in the dormant state exhibit high resistance to sanitizers and my also be part of biofilms. Consequently, enhanced sanitation methods are required for control. Therefore, the research will be of value to the CPMA in providing recommendations to members for more reliable diagnostics to detect Listeria and risk management options for its control.

A one-step natural postharvest wash for safer and longer-lasting Canadian fresh produce

Tianxi Yang

Fresh fruits and vegetables are central to healthy diets and to the economic strength of the Canadian produce supply chain, yet the sector continues to face linked postharvest challenges, including pesticide residues, microbial contamination, spoilage, water-intensive washing, and growing consumer demand for cleaner and more sustainable handling practices. These challenges are especially important for highly perishable commodities such as berries, grapes, and other soft fruits, where safety, quality, and shelf life can change rapidly during packing, distribution, retail display, and household storage.

The overall objective of project is to develop and evaluate a food-grade, plant-based metal-phenolic network (MPN)-protein wash as a practical postharvest strategy to improve the safety and shelf life of selected fresh produce by reducing pesticide residues and surface microbial contamination while maintaining produce quality during storage. This project builds directly on our recent preliminary study1, in which we developed a dual-function MPN-capped starch nanoparticle postharvest wash for pesticide removal and produce preservation (Figure 1). That study demonstrated the feasibility of using natural, biodegradable MPN-based materials to remove pesticide residues from fruit surfaces and slow postharvest deterioration. The current CPMA project advances this platform by developing an MPN-protein formulation based on soy protein isolate, natural polyphenols, and food-compatible metal ions. Metal–phenolic network (MPN) is coordination assemblies formed between metal ions and natural phenolic ligands, combining the strong coordination ability and intrinsic antibacterial activity2. Soy protein will be selected because its diverse functional groups provide more interaction sites than starch alone, potentially enhancing contaminant binding, surface adhesion, and preservation performance. It is also a food-compatible, nutritionally valuable material with strong potential for developing high-value edible coatings. Soy protein isolate contains amino, carboxyl, hydroxyl, hydrophobic, and aromatic groups, which have great potential to interact with pesticide molecules, microbial cell surfaces, and produce surfaces through hydrogen bonding, electrostatic attraction, hydrophobic interactions3. When incorporated into MPN structures, these functional groups may strengthen contaminant adsorption, microbial capture or reduction, and produce-surface adhesion. Therefore, this project advances the MPN concept by testing a protein-based formulation that may be better suited for a practical one-step wash targeting pesticide removal, microbial reduction, and short-term produce preservation.

In this project, we will focus on selected high-value perishable produce, such as strawberries, raspberries, and grapes, and will use representative pesticide and microbial models relevant to produce safety and spoilage. Rapid analytical tools, including surface-enhanced Raman spectroscopy (SERS), microscopy, and selected machine-learning-assisted data analysis, will be used to quantify residue removal, microbial reduction, and key shelf-life outcomes.

The specific objectives are as follows, 1) Optimize an MPN-protein formulation for removing selected representative pesticide residues from model fresh produce. 2) Evaluate the ability of the optimized treatment to reduce representative surface microbial contamination related to produce safety and spoilage. 3) Assess the effect of the treatment on key postharvest quality indicators, including appearance, weight loss, firmness, visible spoilage, and shelf life during storage. 4) Conduct integrated validation by comparing the optimized treatment with common washing or sanitation controls under practical storage conditions.

CPMA support is well matched to this project because the work is directly focused on food safety, postharvest quality, and best practices for the Canadian produce industry. The fund’s investment would move the technology from promising laboratory findings toward an industry-relevant validation package, including clear performance data, practical treatment conditions, and comparison with current washing approaches.