Durability Assessment of a Plasma-Polymerized Coating with Anti-Biofilm Activity against L. monocytogenes Subjected to Repeated Sanitization

Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).[EN] Biofilm formation on food-contact surfaces is a matter of major concern causing food safety and spoilage issues to this sector. The aim of this study was to assess the durability of the anti-biofilm capacity of a plasma-polymerized coating composed of a base coating of (3-aminopropyl) triethoxysilane (APTES) and a functional coating of acrylic acid (AcAc). Coated and uncoated AISI 316 stainless steel (SS) plates were subjected to five sanitization cycles with sodium hypochlorite (0.05%) and peracetic acid (0.5%). The effectiveness of the coating for the inhibition of multi-strain Listeria monocytogenes biofilm formation was confirmed using a three-strain cocktail, which was grown on the SS plates at 12◦ C for 6 days. Compared to the uncoated SS, relative biofilm productions of 14.6% on the non-sanitized coating, 27.9% on the coating after sanitization with sodium hypochlorite, and 82.3% on the coating after sanitization with peracetic acid were obtained. Morphological and physicochemical characterization of the coatings suggested that the greater anti-biofilm effectiveness after sanitization with sodium hypochlorite was due to the high pH of this solution, which caused a deprotonation of the carboxylic acid groups of the functional coating. This fact conferred it a strong hydrophilicity and negatively charged its surface, which was favorable for preventing bacterial attachment and biofilm formation.SIThis publication is based upon work from COST Action CA19110—PlAgri, supported by COST (European Cooperation in Science and Technology-www.cost.eu). XPS tests were conducted by the Advanced Microscopy Laboratory (LMA) of The Institute of Nanoscience of Aragón (INA), University of Zaragoza. The authors are thankful to the LMA-INA for the access to their equipment and their expertise. The AFM images were taken by the Central Research Support Service (SCAI) of the University of Málaga (UMA). The author P. Fernández-Gómez is grateful to Junta de Castilla y León and the European Social Fund (ESF) for awarding her a predoctoral grant (BOCYL-D-15122017-4). The author M. Oliveira is in receipt of a Juan de la Cierva contract IJC2018-035523-I awarded by the Spanish Ministry of Science, Innovation, and Universities MCIN/AEI/10.13039/501100011033. The author E. Sainz-García, as researcher of the University of La Rioja, is thankful to the postdoctoral training program funded by the Plan Propio of the University of La Rioja. The authors I. Muro-Fraguas and A. Sainz-García are thankful to the program of pre-doctoral contracts for the training of research staff that is funded by the University of La Rioja.This study is part of the Research, Development and Innovation projects AGL2017-82779- C2-R and PID2020-113658RB-C2, funded by MCIN/AEI/10.13039/501100011033 and by ERDF “A way to make Europe”

A Review on Non-thermal Atmospheric Plasma for Food Preservation: Mode of Action, Determinants of Effectiveness, and Applications

Non-thermal Atmospheric Plasma (NTAP) is a cutting-edge technology which has gained much attention during the last decade in the food-processing sector as a promising technology for food preservation and maintenance of food safety, with minimal impact on the quality attributes of foods, thanks to its effectiveness in microbial inactivation, including of pathogens, spoilage fungi and bacterial spores, simple design, ease of use, cost-effective operation, short treatment times, lack of toxic effects, and significant reduction of water consumption. This review article provides a general overview of the principles of operation and applications of NTAP in the agri-food sector. In particular, the numerous studies carried out in the last decade aimed at deciphering the influence of different environmental factors and processing parameters on the microbial inactivation attained are discussed. In addition, this review also considers some important studies aimed at elucidating the complex mechanism of microbial inactivation by NTAP. Finally, other potential applications of NTAP in the agri-food sector, apart from food decontamination, are briefly described, and some limitations for the immediate industrial implementation of NTAP are discussed (e.g., impact on the nutritional and sensory quality of treated foods; knowledge on the plasma components and reactive species responsible for the antimicrobial activity; possible toxicity of some of the chemical species generated; scale-up by designing fit-for-purpose equipment)

Organoleptic characterization of wines in contact with oak wood fragments immersed in plasma activated water (PAW)

Oak barrels are a valuable material for wine ageing, although their difficult cleaning and disinfection favours microbiological contamination causing wine quality depreciation. Atmospheric pressure cold plasma is a suitable technique to reduce microbiota, but there is little research on its impact on the nutritional and sensory characteristics of foods. The aim of this study was to analyse the organoleptic characteristics of red wines in contact with plasma-activated waters (PAW) treated wood, of different origins and toasting levels. These red wines were compared with others that had been in contact with two types of control wood; some immersed in distilled water and others subjected to sulphur dioxide combustion. The results showed that oak wood treated with PAW did not cause defects at the olfactory and gustatory level of the red wines, which presented good harmony, sufficient body and balanced fruity and spicy notes, sometimes even superior to those described for red wines in contact with control wood (sulphited or submerged in distilled water). Therefore, the treatment of the wood with PAW did not have a negative impact on the sensory quality of the wines, regardless of the origin and toasting of the wood

Aplicación de recubrimientos funcionales sobre vidrio empleando plasma atmosférico frío

Los recientes avances en las técnicas para la generación de plasma han dado lugar al desarrollo de tecnologías de plasma atmosférico frío, cuya capacidad para llevar a cabo tratamientos superficiales las ha convertido en un foco de interés de cara a su implantación en la industria. Una de las características más atractivas de esta tecnología es la posibilidad de modificar determinadas propiedades funcionales de los materiales sin someterlos a grandes variaciones de presión o temperatura que pudieran provocar cambios no deseados en otras. Con esta tesis, que engloba los resultados de tres publicaciones científicas, se pretende demostrar la utilidad de los procesos de plasma-polimerización con tecnologías de plasma atmosférico frío para abordar los problemas asociados al vidrio empleado en las industrias de las energías renovables y del automóvil. Para ello, en dichos trabajos se ha utilizado un sistema de chorro de plasma a presión atmosférica (Atmospheric Pressure Plasma Jet, APPJ) para depositar recubrimientos sobre sustratos de vidrio mediante plasma-polimerización, los cuales se han estudiado mediante análisis morfológicos, químicos y funcionales. En el marco de las energías renovables, en los dos primeros trabajos presentados se estudia la aplicación de diversos recubrimientos para promover el carácter hidrófugo y la resistencia al desgaste del vidrio empleado en paneles solares. Estos recubrimientos pretenden reducir el impacto negativo que tienen la suciedad y el deterioro superficial en la ya de por sí limitada eficiencia de estos elementos. En cada uno de estos trabajos se emplean mezclas de dos precursores líquidos, con distintas composiciones químicas, cada uno de ellos especialmente escogido como proveedor de cada una de las propiedades funcionales objetivo. Puesto que la hidrofugacidad y la resistencia al desgaste presentan tendencias opuestas (cuanto mayor es una, menor suele ser la otra), un aspecto clave de estos trabajos consiste en determinar en qué proporciones deben mezclarse los precursores empleados para obtener un recubrimiento satisfactorio en ambas propiedades. Por ello, en cada trabajo se analizan recubrimientos obtenidos a partir de mezclas de precursores en distintas proporciones (del 0% al 100%). En el marco de la industria automovilística, en el tercer trabajo busca una disminución de la fricción mediante la aplicación de recubrimientos por plasma-polimerización sobre el vidrio. Estos recubrimientos pretenden ser una alternativa a las actuales soluciones empleadas en aquellas partes en las que éste se desliza contra otros elementos del vehículo, tales como los limpiaparabrisas y las juntas de estanqueidad de las ventanillas. Utilizando un único precursor, y con el fin de determinar qué condiciones del proceso de plasma-polimerización favorecen la reducción del coeficiente de fricción, en este trabajo se analizan recubrimientos obtenidos suministrando distintos niveles de potencia y aplicando distintas cantidades de pasadas sucesivas. El espesor de los recubrimientos y su composición química parecen determinar su comportamiento tribológico, siendo necesarios un espesor y un carácter inorgánico lo suficientemente elevados para reducir de manera efectiva el coeficiente de fricción del vidrio. Se considera que, con los resultados obtenidos en esta tesis, se han satisfecho los objetivos planteados. Esto demuestra las prometedoras aplicaciones de las tecnologías de plasma atmosférico frío en industrias tan importantes como la de las energías renovables y la automovilística