Effects of cold atmospheric plasma treatments on decontamination of processing wash water, safety and quality of leafy vegetable products.

In order to ensure the microbial quality and safety of ready-to-eat vegetables, washing of fruits and vegetables is a critical step in the fresh produce processing industry. Washing contributes to the reduction in microbial contamination by spoilage and pathogenic bacteria, e.g. Escherichia coli, Listeria monocytogenes and Salmonella, as well as removal of traces of pesticides from the product surface. Adequate sanitizing treatments are required before wash waters are discarded or reused since they quickly accumulate solids, organic matter, and microbial contaminants. As recycled water used in food processing must satisfy the same standards as drinking water according to the EU legislation, decontamination of wash water is generally achieved through chemical or physical practices such as treatments with sodium hypochlorite, oxidizing agents, UVC or ozone. Recent studies have shown that two emerging technologies, Cold Atmospheric Plasma and Plasma Activated Water (PAW), are successful against a variety of foodborne pathogens and spoilage bacteria in different food matrices. The aim of the study was to test the technology to evaluate its potential in decontaminating wash water. The performances of the plasma treatments were compared to the current industry standard procedure for water sanitation. Water quality (COD, BOD) and effectiveness in reducing viability of the main microbial spoilage populations were measured for different operational settings. Plasma-treated wash waters were also used to wash/rewash fresh leafy vegetables. Immediately after the treatments, the effects on natural spoilage microorganisms and product quality (pH, colour and total phenolic content) were evaluated. Overall, the results showed that plasma technologies can be a promising solution for the food industry to ensure safety and microbiological quality of both washing water and leafy vegetables, with the possibility of water sanitation, water reuse and water saving.