2 results
Search Results
Now showing 1 - 2 of 2
- ItemPlasma-Functionalized Water: from Bench to Prototype for Fresh-Cut Lettuce(New York : Springer, 2020) Schnabel, Uta; Handorf, Oliver; Stachowiak, Joerg; Boehm, Daniela; Weit, Christoph; Weihe, Thomas; Schäfer, Jan; Below, Harald; Bourke, Paula; Ehlbeck, JoergFresh-cut produce like lettuce may contain a very high microbial load, including human pathogens. Therefore, the need for antimicrobial agents at post-harvest stages to mitigate microbial cross-contamination and growth is evident. Sanitation based on non-thermal plasma (NTP) reveals innovative food processing possibilities by application at different points along the food chain, for production, modification, and preservation, as well as in packaging of plant- and animal-based food. The aim of the present study was to evaluate the applicability of plasma-treated water (PTW) as antimicrobial process water additives for washing in fresh-cut lettuce processing. Antibacterial activities of PTW the natural occurring microflora of lettuce were examined. Different process variants of PTW application inside the washing process were investigated. Fresh-cut lettuce were investigated regarding microbiological safety and food quality. Samples were analyzed for antimicrobial and metabolic activity as well as metabolic vitality to prove food safety. The investigations for food quality included color and texture analyses and nitrate concentration detection in fresh tissue as well as microscopic measurements by scanning electron microscopy (SEM) and atomic force microscopy (AFM) for tissue surface structure and transmission electron microscopy (TEM) for cell organelle investigations. The application of PTW allowed up to 5 log10 cycle reduction, depending on the process variant and scale (lab and pilot scale). The increase of antimicrobial activity was accompanied by a reduction of metabolic activity, but not consequently by a decrease in metabolic vitality. Food quality was not affected by the use of PTW in the washing process of the fresh-cut lettuce. The promising results in color and texture were supported by the results of the microscopic assays. These promising results may lead to an industrial application of PTW as process water additive in fresh-cut produce processing to reduce the microbial load on the food surface and in addition in the process water or on food processing surfaces. © 2020, The Author(s).
- ItemOptimizing the application of plasma functionalised water (PFW) for microbial safety in fresh-cut endive processing(New York, NY [u.a.] : Elsevier Science, 2021) Schnabel, Uta; Balazinski, Martina; Wagner, Robert; Stachowiak, Jörg; Boehm, Daniela; Andrasch, Mathias; Bourke, Paula; Ehlbeck, JörgThe 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.Industrial relevance 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.