Dielectric barrier discharge treatments at atmospheric pressure for wood surface modification

In this research, the effect of dielectric barrier discharge on mechanically manufactured (sawn, planed or polished) wood surfaces is investigated. The experiments have shown that the best hydrophilia is obtained with a cold plasma discharge in air under atmospheric pressure. Other gases such as helium, nitrogen, and argon have been tested, too. Changes of the wood surface properties were determined by absorption of water and contact angle measurements. As a result of a 1 to 20 seconds long exposure to plasma, wood surfaces became hydrophilic. The absorption of water in wood can be changed up to 22 times higher after plasma treatment in air for 20 seconds duration. The fracture strength of glued wood has been increased by 68% after this plasma pretreatment. Using plasma treatment in methane or acetylene wood surfaces are changed to hydrophobic properties. After plasma treatment for 1 min. in a Ar:CH₄=80:20 gas mixture under atmospheric pressure, the absorption of water in wood is 32 times lower than without plasma treatment. As mentioned before, plasma treatment can produce hydrophobic and hydrophilic wood surfaces. But a good homogeneity of the gas discharge is necessary for the plasma treatment of wood. Zusammenfassung Im Rahmen dieser Arbeit werden die Auswirkungen der dielektrisch behinderten Entladung bei Atmosphärendruck auf mechanisch bearbeitete Holzoberflächen (gesägt, gehobelt oder geschliffen) untersucht. Die Experimente haben gezeigt, dass die höchste Hydrophilität bei einem in Luftatmosphäre gezündetem Plasma erreicht wird. Es werden auch andere Gase verwendet, wie z.B. Helium, Stickstoff und Argon. Zur Untersuchung der veränderten mechanischen und energetischen Eigenschaften der Holzoberflächen werden der Tropfen-Versuch und die Kontaktwinkelmessung verwendet. Durch eine 1 bis 20 Sekunden lange Plasmabehandlung können die Oberflächen hydrophil gestaltet werden. So kann die Eindringzeit von Wasser um Faktor 22 gesteigert werden durch eine 20 Sekunden lange Plasmabehandlung in Umgebungsluft. Die Bruchfestigkeit von Leimholz wird durch die gleiche Plasmavorbehandlung um 68% gesteigert. Werden als Plasmabehandlungsgas Methan oder Acetylen eingesetzt, so wird die Holzoberfläche hydrophob. Durch eine 60 Sekunden lange Plasmabehandlung in einem Ar:CH₄=80:20 Gasgemisch bei Atmosphärendruck wird die Eindringszeit von Wasser um den Faktor 32 gesenkt. Mit Hilfe der Plasmabehandlung können also sowohl hydrophobe als auch hydrophile Holzoberflächen erzeugt werden. Jedoch wird für die Plasmabehandlung von Holz eine sehr homogene Gasentladung benötigt.     

Dielectric barrier discharge treatments at atmospheric pressure for wood surface modification

In this research, the effect of dielectric barrier discharge on mechanically manufactured (sawn, planed or polished) wood surfaces is investigated. The experiments have shown that the best hydrophilia is obtained with a cold plasma discharge in air under atmospheric pressure. Other gases such as helium, nitrogen, and argon have been tested, too. Changes of the wood surface properties were determined by absorption of water and contact angle measurements. As a result of a 1 to 20 seconds long exposure to plasma, wood surfaces became hydrophilic. The absorption of water in wood can be changed up to 22 times higher after plasma treatment in air for 20 seconds duration. The fracture strength of glued wood has been increased by 68% after this plasma pretreatment. Using plasma treatment in methane or acetylene wood surfaces are changed to hydrophobic properties. After plasma treatment for 1 min. in a Ar:CH₄=80:20 gas mixture under atmospheric pressure, the absorption of water in wood is 32 times lower than without plasma treatment. As mentioned before, plasma treatment can produce hydrophobic and hydrophilic wood surfaces. But a good homogeneity of the gas discharge is necessary for the plasma treatment of wood.     

介质阻挡放电等离子体对印染废水的脱色处理

在不加任何助剂的情况下,等离子体发生器产生的高能粒子、臭氧以及紫外光的联合作用,可以有效地降解各类有机物.试验用介质阻挡放电等离子技术(DBD)对初始浓度40mg/L的雅格素红3BF进行脱色和降解处理5 min(放电间隙为10mm),雅格素红3BF的脱色率可以达到91.7％.随着处理时间的延长,首先是偶氮基团的破坏,随后是芳香类基团的降解.染液初始浓度越高,最终脱色率越低;放电间隙越窄,越有利于脱色.     

Antibacterial effects of non-thermal dielectric barrier discharge plasma against Escherichia coli and Vibrio parahaemolyticus on the surface of wooden chopping board

In this study, the effects of atmospheric dielectric barrier discharge (DBD) plasma treatment (1.1 kV, 43 kHz, 5–30 min, N₂: 1.5 lpm) were investigated for the inactivation of Escherichia coli and Vibrio parahaemolyticus on wooden chopping board (WCB) surfaces. A reduction of 0.4–1.6 and 0.4–1.3 log CFU/coupon was observed for E. coli and V. parahaemolyticus, respectively, on the WCB surface by DBD plasma treatment. The first-order kinetics model was used to generate linear survival curves and calculate D-values and R² for the bacteria; D-values were 41.0 min and 59.8 min, and R² values were 0.94 and 0.97 for E. coli and V. parahaemolyticus, respectively. Based on these findings, DBD plasma could potentially serve as a new antimicrobial method for wooden cutting boards.     

Dielectric barrier discharge plasma for microbial decontamination of dried laver: effects on physicochemical characteristics

Dielectric barrier discharge (DBD) plasma in atmospheric pressure air was used for microbial decontamination of thin sheets of dried laver, which are commonly used in kimbab preparation. Microbial contaminants namely aerobic bacteria, moulds and marine bacteria were found in sun‐dried laver sheets. DBD plasma was generated at an output voltage of 30 kV AC and a frequency of 30 kHz. Upon the plasma treatment of laver, 2.5‐log (99.68%), nearly 1.5‐log (96.84%) and above 1.0‐log (90%) unit reductions in viable counts of aerobic bacteria, marine bacteria and moulds were observed over a 10‐min period, respectively. The inactivation pattern fitted well to Singh–Heldman model or pseudo first‐order kinetics. Compared to control laver, no significant (P > 0.05) changes in the colour characteristics, total phenolic content and 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity were observed in plasma‐treated laver. Furthermore, DBD plasma‐treated laver sheets had exerted no negative impact on the sensory characteristics of kimbab and can extend the shelf life.     

Improved solubility of banana starch by dielectric barrier discharge plasma treatment

A novel technology for banana starch modification has been developed using dielectric barrier discharge (DBD) plasma, and the effect of DBD plasma treatment on the solubility and pasting behaviours of banana starch were evaluated. The solubility of treated starch significantly increased from 1.35 to 15.05 g 100 g⁻¹ at 55 °C as the treatment intensity increased. Rapid viscosity analyser examination showed a dramatic change in the pasting behaviours of modified starch, and the peak viscosity decreased from 5242.0 to 153.0 (cP) as the treatment intensity increased. Evidence of nonpenetrative damage caused by plasma etching was shown by scanning electron microscope micrographs. The results of X-ray diffraction and Fourier-transform infrared spectroscopy analyses indicated that the DBD treatment changed the granular structure of banana starch.     

介质阻挡放电低温等离子体的产生

介绍利用介质阻挡电极放电产生低温等离子体的方法,分析了在大气压下介质阻挡电极放电的细丝模式和均匀辉光模式（APGD）的特点.通过电压-电流波形图和电压-电荷李萨育图形,比较了细丝模式和扩散模式的区别,并分析了两者在产生低温等离子体的物理机制.     

Inhibition of enzymes and Pseudomonas tolaasii growth on Agaricus bisporus following treatment with surface dielectric barrier discharge plasma

In this study the applicability of cold plasma, produced by surface dielectric barrier discharge (SDBD), to inactivate Pseudomonas tolaasii (P.tolaasii), polyphenol oxidase (PPO) and peroxidase (POD) enzymes, as well as its impact on quality parameters such as, color, texture, pH and weight loss were evaluated. The study evidently shows that treating with combination of 30% hydrogen peroxide vapor)with flow rate of 0.47 mL min⁻¹) and argon (H₂O₂ + Ar) for 180 s is capable of reducing the activity of PPO (0.17 U min⁻¹ g⁻¹ FW) and POD (0.21 U min⁻¹ g⁻¹ FW) and increasing the SOD enzyme (16.29 U g⁻¹ FW) in a 21-day storage period compared to control samples. This is while the quality characteristics of button mushroom are preserved during storage after such treatment.Industrial relevanceThis study provides information of A. bisporus storage during 21-day period after SDBD plasma treatment, which is rarely. Greater inactivation of P. tolaasii after 180 s treatment with combination of hydrogen peroxide vapor and air (H₂O₂ + air) was shown compared to control samples, but this treatment caused also slightly degradation of button mushroom color. A better reduction of PPO and POD enzyme activity as well as further increase of SOD enzyme activity was observed following treatment with 180 s of H₂O₂ + Ar gas in a 21-day storage period. This research work contributes to the understanding SDBD plasma induced effects on the shelf-life of button mushroom and could be a basis for a possible industrial implementation.     

Inactivation of Alicyclobacillus contaminans spores by dielectric barrier discharge plasma and its biological mechanism

Over the years, as an emerging technology, cold plasma (CP) has been widely used in the preservation of agricultural products. Alicyclobacillus spp. are spore-forming bacteria and difficult to inactivate. They adversely affect the economic value of agricultural products. Nevertheless, there are still few studies related to the inactivation of spores using CP. Herein, the inactivation effect and mechanism of dielectric barrier discharge plasma (DBDP) on Alicyclobacillus contaminans (A. contaminans) spores in phosphate-buffered saline and clarified apple juice were investigated. Plasma treatment at 75 V for 9 min achieved 99% inactivation of spores with the initial inocula of 7.13 and 5.72-log in PBS and apple juice, respectively. And the cell structure of the spores was severely disrupted leading to the leakage of the entocyte. Moreover, the surface properties of the spores were altered, making the adhesion of the spores to the hydrophobic surfaces and the stability of the bacterial suspension decreased leading to more agglomeration of the spores. Further results confirmed the intracellular homeostasis of the spores was also disrupted. Therefore, the inactivation mechanism of DBDP on spores was revealed from different perspectives, and our discoveries promote the theoretical progress in the use of plasma in food sterilization.Industrial relevanceAs an emerging nonthermal preservation technology, cold plasma has been used in food processing. In this study, we confirmed the feasibility of the inactivation of Alicyclobacillus contaminans spores in apple juice by dielectric barrier discharge plasma (DBDP) and investigated the mechanism of plasma inactivation of spores at the molecular biology level. This paper provides preliminary support for the application of low-temperature plasma in food processing such as apple juice.     

Effects of dielectric barrier discharge plasma on the physicochemical and functional properties of myofibrillar proteins

The present study was designed to investigate the effects of dielectric barrier discharge (DBD) plasma on myofibrillar proteins extracted from beef. For this purpose, myofibrillar proteins were extracted from Longissimus dorsi muscle and treated with DBD plasma for 0, 5, 10, 15, and 20 min to evaluate free sulfhydryl and carbonyl, FTIR, and DSC profiles as well as pH, color, foaming capacity and stability, emulsion capacity and stability, and water binding capacity of myofibrillar proteins. Evaluation of the chemical changes revealed that protein oxidation was the main event occurring during exposure to DBD plasma. Moreover, mild oxidation during the first 10 min of exposure was found to improve the functional properties of myofibrillar proteins such that significant (p < 0.05) increases were observed not only in foaming capacity but also in emulsion capacity and stability. However, the detrimental effects of severe oxidation on functional properties due to long-time exposure cannot be ignored. This is while long-time exposure was observed only to lead to significantly (p < 0.05) improved water binding capacity (WBC) (rising it from ~25% in the control treatment to ~92% in the 20-min treatment). The findings of this study can be beneficially exploited by the food industry toward appropriate treatment of myofibrillar proteins with non-thermal plasma.     

常压等离子体引发亚麻接枝丙烯酸的工艺条件

研究了大气压介质阻挡放电引发亚麻接枝丙烯酸的工艺条件。结果表明，接枝率随着等离子体处理时间、接枝温度和接枝溶液浓度的增加而出现最大值，并随着等离子体处理电压、接枝时间的增加而增加。合适的处理条件为：等离子体处理时间30s、电压为28kV、接枝温度70℃、接枝时间2h、接枝溶液浓度60％。     

Antibiofilm mechanism of dielectric barrier discharge cold plasma against Pichia manshurica

Biofilm spoilage has become one of the most common concerns in fermented foods. The objective of the present study was to explore the biofilm-inhibitory effect and antibiofilm mechanism of dielectric barrier discharge (DBD) cold plasma on Pichia manshurica (a species of yeast responsible for biofilm spoilage in fermented foods). After plasma treatment (80 kV, 50 Hz) for 4.5 min and 7.5 min, viable counts decreased by 2.38 and 5.11 lg CFU/mL, respectively, and the biofilm-forming rate decreased to 73% and 48% of the control group, respectively, in microbiological media. In addition, DBD caused severe morphological damage, cell membrane permeabilization and metabolic changes. A number of amino acid metabolic pathways, the tricarboxylic acid cycle (TCA), and the synthesis of extracellular polymeric substance (EPS) were destroyed. The cell damage and changes in multiple metabolic activities led to significant inhibitory effects on Pichia manshurica and its biofilm-forming ability.Industrial relevanceThis study found that DBD can significantly inhibit the biofilm-forming ability of Pichia manshurica (a species of yeast responsible for biofilm spoilage in fermented foods) by causing severe cell damage and metabolic changes. The exploration of the biofilm inhibitory effect of DBD on Pichia manshurica and its mechanism can provide a theoretical basis for the application of DBD technology in the inhibition of biofilm spoilage in foods.     

均匀介质阻挡放电用于材料表面改性的进展

在一定的条件下,大气压DBD能产生均匀、稳定的辉光放电,称为均匀DBD或大气压辉光放电(APGD).与丝状DBD相比,均匀DBD具有放电均匀、功率密度适中等优点,可以对材料表面进行更为均匀处理,因此具有更好的应用前景.在总结大量国内外文献的基础上,介绍了均匀介质阻挡放电(DBD)的产生结构和影响因素,综述了国内外均匀DBD材料表面改性的研究进展,并分析了改性中存在的主要问题及可能的解决办法.     

介质阻挡放电等离子体处理对玉米淀粉结构和功能性质的影响

目的 研究低温介质阻挡放电等离子体对高直链玉米淀粉和蜡质玉米淀粉的多尺度结构及功能性质的影响。方法 以高直链玉米淀粉(high-amylose corn starch, HAMS)和蜡质玉米淀粉(waxy maize starch, WMS)为研究对象, 采用介质阻挡放电等离子体技术, 控制输入电压110 V, 调节输入电流为0.8、1.0、1.2和1.4 A, 分别对淀粉粉体进行改性处理1 min, 探究两种淀粉在不同处理电流下等离子体场中的多尺度结构和理化功能性质的变化。结果 经过等离子体处理后, 两种淀粉颗粒的粒径增大, HAMS颗粒出现团聚现象, WMS的表面孔道和刻蚀现象更加明显, 淀粉乳的pH降低, 其溶胀力和成糊黏度均呈现降低的趋势, 其中WMS峰值黏度从3113.50 cP显著降低至795.50 cP。随着处理电流的增加, 两种玉米淀粉的吸热相转变焓值降低, 其中蜡质玉米淀粉焓值从(13.83±0.07) J/g降低至(8.20±0.03) J/g, 广角X射线衍射结果显示淀粉相对结晶度逐渐降低, 而傅立叶变换红外光谱法分析发现红外比值R1047/1022和R1022/995分别略微下降和升高。结论 等离子体处理对WMS的改性效率相比HAMS较大, 等离子体改性处理主要影响玉米淀粉的长程晶体结构, 而对短程双螺旋结构的影响较为有限。     

Aflatoxins degradation and quality evaluation in naturally contaminated rice by dielectric barrier discharge cold plasma

In this study, dielectric barrier discharge (DBD) cold plasma was explored for degrading aflatoxins in naturally contaminated rice. Rice samples were inoculated with strains of toxigenic Aspergillus and incubated to produce various levels of aflatoxins. Cold plasma showed degradation rates of aflatoxin B₁ (AFB₁) and total aflatoxins (AFs) that were related to moisture content, oxygen content, treatment time and voltage. Generally, the treatment reduced 1.08%–55.34% of AFB₁ and 4.23%–56.37% of AFs in rice under different conditions. Relative lower degradation rates can be due to low permeability of the plasma and interference from food matrix. In addition, no significant difference (P > 0.05) was found in moisture, protein, amylose and color of rice before and after treatment. However, cold plasma aggravated the fat oxidation of rice, and made its surface smoother and more porous. The results provided a theoretical basis for aflatoxins degradation from grain system using cold plasma.Industry relevanceIn this study, dielectric barrier discharge (DBD) cold plasma was applied in the degradation of aflatoxins in naturally contaminated rice, having obvious degradation effect and little quality impact. Cold plasma treatment, as a novel non-thermal processing technology, can reduce mycotoxins in food in order to fully ensure the product safety in various links, including production, storage and so on. Compared with other detoxification methods currently used in the industry, this technology can achieve similar or higher degradation effect in a shorter time. In addition, it is low-cost and will not pollute the environment or damage the sensory properties and nutritional value of products.     

Application of phosphorescent oxygen sensors in in-package dielectric barrier discharge plasma environment

Dielectric barrier discharge plasma treatment of two different types of phosphorescent oxygen sensors under different in-package gas mixture has been studied. Commercial Optech™-O₂ platinum and microporous polypropylene (PP) membrane sensors impregnated with platinum benzoporphyrin (PtBP) dye were found effective for oxygen sensing when DBD plasma treated under modified atmospheric conditions. When treated under DBD air plasma, PP sensors were largely degraded and found incompatible with the plasma processing. Although some changes in the lifetime signals were observed after air plasma treatment, Optech™-O₂ platinum sensors were found effective as oxygen sensors. This study indicates that in-package gas composition of food products plays an important role in selection of right intelligent optochemical sensors for plasma processing.Industrial RelevanceIn-package cold plasma processing is emerging as a novel and innovative approach for the decontamination of food products with significant potential for commercial application. This paper studies the compatibility of phosphorescent oxygen sensors with this technology. This study demonstrates that the package gas composition has huge impact on the accuracy and usability of sensors. The work described in this research is relevant to all food industries which uses intelligent sensors for monitoring gas composition.     

Inactivation kinetics of polyphenol oxidase and peroxidase in pineapple juice by dielectric barrier discharge plasma technology

The non-thermal plasma technique is an innovative non-thermal approach for food preservation and decontamination. Polyphenol oxidase (PPO) and peroxidase (POD), the principal food degrading enzymes in pineapple juice, were inactivated by the Dielectric Barrier Discharge (DBD) plasma. The inactivation kinetics of PPO and POD in pineapple juice were examined at three different voltages 25, 35, and 45 kV for up to 10 min of plasma treatment. The present study's findings revealed that plasma parameters such as voltage and treatment time substantially reduced enzyme activity of both enzymes, with the former parameter having a more pronounced influence on enzyme inactivity. To mathematically represent the model parameters, established kinetic models viz. log-linear, Weibull, and logistic were fitted to observe experimental data. The Weibull model was discovered to be the best fit for the enzyme inactivation kinetics. The scale factor for PPO was 15.95, 10.87, and 5.73 min at 25, 35, and 45 kV, respectively which was lower than POD with scale factor 40.74, 19.76, and 7.28, respectively. This shows that POD was more resistant to inactivation by DBD plasma than PPO.     

Inactivation effect of dielectric barrier discharge plasma against foodborne pathogens on the surfaces of different packaging materials

The usefulness of dielectric barrier discharge (DBD) plasma for surface disinfection of the common food packaging materials, namely glass, polyethylene, polypropylene, nylon, and paper foil was evaluated. DBD plasma was generated by applying a pulsed DC voltage of 10 kV and at a power of 208 W. The separation distance between the electrodes was 2.65 mm. On exposure of food pathogens-loaded packaging materials to the plasma, > 4 log/cm² reduction (99.99%) in viable cell counts of Escherichia coli O157:H7 was observed in 10 min. The other two tested pathogen strains, Salmonella typhimurium and Staphylococcus aureus, were inactivated in the range 3.0–3.5 log/cm². The inactivation pattern of the pathogens fitted well to the log-linear and tail model. Compared to unexposed packaging materials, no significant (p > 0.05) changes in the surface temperatures, optical characteristics, tensile strengths, and strain-induced deformation were observed for the DBD plasma-exposed materials. Therefore, the DBD plasma can be used to disinfect surfaces of different food packaging materials harboring moderate levels of bacterial contaminants without adversely affecting their physicomechanical properties.Industrial relevanceTraditionally, dry heat, steam, UV light and chemicals like ethylene oxide and hydrogen peroxide have been used as surface sterilants and disinfectants for packaging materials in the food industry. However, certain limitations have motivated the search for new approaches. Cold plasma technology is an emerging, green process for surface sterilization. The DBD plasma was found to be effective in reducing the bacterial food pathogens on different food packaging materials. As the technology is simple and scalable, it can be readily applied industrially.