Optimizing the application of plasma functionalised water (PFW) for microbial safety in fresh-cut endive processing

• Published in: Innovative food science & emerging technologies Vol. 72; p. 102745
• Main Authors: Schnabel, Uta, Balazinski, Martina, Wagner, Robert, Stachowiak, Jörg, Boehm, Daniela, Andrasch, Mathias, Bourke, Paula, Ehlbeck, Jörg
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2021
• Subjects: Food safety; Leafy greens; Microwave-driven discharge; Non-thermal processing; Ready-to-eat produce; Ready-to-eat produce; Food safety; Leafy greens; Microwave-driven discharge; Non-thermal processing
• ISSN: 1466-8564; 1878-5522
• DOI: 10.1016/j.ifset.2021.102745

The microbiological profiles and responses of native microflora of endive were investigated using a model process line, to establish where a defined PFW should be optimally applied to retain or improve produce microbiological quality. The PFW processes were compared with tap water and ClO2. The antimicrobial efficacy of PFW was quantified by determining the reduction in microbial load, the microbial viability and vitality. Depending on the stage of application of PFW, up to 5 log10-cycles reduction was achieved, accompanied by a reduction of metabolic activity, but not necessarily with a decrease in metabolic vitality. Multiple application (3-step-PFW-application) was more effective than single application (1-step-PFW-application) and PFW showed stronger antimicrobial effect in pre-cleaned endive. High concentrations of nitrite (315 mg l−1) and nitrate (472 mg l−1) in PFW were the main factors for the antimicrobial efficacy of PFW against bacteria. Furthermore, H2O2 and an acidic pH supported the mechanism of action against the endive microflora. These results identify the pathway to scale up successful industrial application of PFW targeting microbiological quality and safety of fresh leafy products. The safety, quality and shelf life of freshly cut vegetables, e.g. lettuce, are strongly influenced by the microbial load. In addition, the hygienic design of production line, and a good handling/ production practice are indispensable. This study shows that the application of PFW, as a promising non-thermal sanitation technology, enables the inactivation of native microbial contamination on fresh-cut endive depending on the process stage of application. It further describes the impact of PFW on the metabolic activity and metabolic vitality of the lettuce-associated microflora. For higher acceptance, the mechanism of action of PFW was assumed based on previous chemical analyses and compared to the industrial standard of ClO2. The results contribute to the understanding and product-specificity of PFW-induced effects on safety, quality and shelf life of fresh cut lettuce and could be a basis for a possible industrial implementation and complement of common technologies. •Plasma functionalised water (PFW) successfully used as wash water additive on lettuce.•PFW treatment enhances the microbiological safety of fresh-cut endive.•PFW showed promising results compared to industry standard chlorine dioxide (ClO2).•Mechanism of action of PFW based on reactive oxygen/nitrogen species (RONS).