Dielectric Barrier Discharge Plasma Treatment Research Articles

E. Coli inactivation by humidified air barrier discharge plasmas and the chemical stability of amino acids

Abstract In this study, we use atmospheric air dielectric barrier discharge (DBD) plasma to inactivate Escherichia coli (E. coli) by changing the air humidity levels. In order to analyze the inactivation process of E. coli during the humidified air DBD plasma treatment, we analyze the byproducts of 12 representational amino acids and compare their chemical stability. The experimental results show that the E. coli surface density (CFU/cm2) on a steel disc decreased significantly when the air humidity was increased from 20% to 60%, and humidified air DBD plasma at 60% humidity is very effective in inactivating E. coli. A consistently potent deactivation effect on E. coli can be seen in plasma afterglow treatment experiments over a storage time of two minutes, indicating that plasma-activated long-lived reactive oxygen and nitrogen species play a crucial role in controlling the E. coli inactivation. Compared to the low humidity (20%) condition, the concentration of reactive species produced by the plasma at high humidity (60%) increased 2-fold for 2-hydroxyterephthalic acid and 5-fold for hydrogen peroxide while ozone production was halved. Amino acid experiments showed that amino acids may be oxidized, hydroxylated and nitroxylated by reactive species. The reduction of amino acids by air DBD plasma was even more pronounced at high air humidity compared to low air humidity. Our analysis indicates that the significant inactivation of E. coli by humified air DBD plasma is related to the chemical instability of amino acids.

Effect of dielectric barrier discharge (DBD) plasma treatment on physicochemical and 3D printing properties of wheat starch

In recent years, the focus has shifted towards carbohydrate-based hydrogels and their eco-friendly preparation methods. This study involved an investigation into the treatment of wheat starch using dielectric barrier discharge (DBD) plasma technology over varying time gradients (0, 2, 5, 10, 15, and 20 min). The objective was to systematically examine the impact of different treatment durations on the physicochemical properties of wheat starch and the suitability of its gels for 3D printing. Morphology of wheat starch remained intact after DBD treatment. However, it led to a reduction in the amylose content, molecular weight, and crystallinity. This subsequently resulted in a decrease in the pasting temperature and viscosity. Moreover, the gels of the DBD-treated starch exhibited superior 3D printing performance. After a 2-min DBD treatment, the 3D printed samples of the wheat starch gel showed no significant improvements, as broken bars were evident on the surface of the 3D printed graphic, whereas DBD-20 showed better printing accuracy and surface structure, compared to the original starch without slumping. These results suggested that DBD technology holds potential for developing new starch-based gels with impressive 3D printing properties.

Human coronavirus 229E inactivation on porous and nonporous materials using dielectric barrier discharge (DBD) plasma.

Viruses can spread through contaminated aerosols and contaminated surface materials, and effective disinfection techniques are essential for virus inactivation. Nonthermal plasma-generated reactive oxygen and nitrogen species can effectively inactivate the coronavirus. We aim to interpret the coronavirus inactivation level and mechanism of surface interaction with materials with and without dielectric barrier discharge (DBD) plasma treatment. Nonthermal plasma, particularly surface-type DBD plasma, can inactivate human coronavirus 229E (HCoV-229E) on porous (paper, wood, mask) and nonporous (plastic, stainless steel, glass, Cu) materials. Virus inactivation was analyzed using a 50% tissue culture infectivity dose (TCID50) using cell line, flow cytometry, and immunofluorescence. Surfaces contaminated with HCoV-229E were treated at different time intervals (0-5 h) with and without plasma exposure (natural decay in ambient air conditions). HCoV-229E persistence conformed to the following order: plastic > cover glass > stainless steel > mask > wood > paper > Cu with and without plasma exposure. HCoV-229E was more stable in plastic, cover glass, and stainless steel in 5 h, and the viable virus titer gradually decreased from its initial log10 order of 6.892 to 1.72, 1.53, and 1.32 TCID50/mL, respectively, under plasma exposure. No virus was observed in Cu after treatment for 5 h. The use of airflow, ambient nitrogen, and argon did not promote virus inactivation. Flow cytometry and immunofluorescence analysis demonstrated a low expression level of spike protein (fluorescence intensity) during plasma treatment and in E and M genes expression compared with the virus control.

Influence of air DBD plasma treatment on the shear and flexural strength of adhesively bonded glass fiber reinforced epoxy composite joints

In this study, air dielectric barrier discharge (DBD) plasma treatment was applied at various voltages and treatment durations to improve the bonding strength of glass fiber reinforced epoxy composites (GF/EP). In addition, single lap shear and three-point bending strengths of adhesively bonded joints were compared between untreated and surface-treated (sanding, peel ply, and plasma) samples. Surface properties of GF/EP composites were examined using contact angle, surface free energy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and Atomic Force Microscopy (AFM). Then, mechanical tests (single lap shear and three point bending) were performed and the damage modes were determined. Surface analyses revealed that wettability and polar functional groups increased on the GF/EP surface after plasma treatment. From the mechanical test results, it was observed that the plasma treatment applied to GF/EP composites increased both single lap shear and flexural strength compared to untreated, sanding and peel ply surface treatments. After both single lap shear and 3-point bending tests, adhesive, and light fiber tear failure modes were observed.

Preventing thermal aggregation of ovalbumin through dielectric-barrier discharge plasma treatment and enhancing its emulsification properties

The impact of Dielectric-Barrier Discharge (DBD) plasma treatment on the prevention of heat-induced aggregation of Ovalbumin (OVA) and improvement in emulsification properties was investigated. Results highlighted the effective inhibition of thermal aggregation of OVA following exposure to plasma. Structural analysis revealed that the plasma-induced oxidation of sulfhydryl and intermolecular disulfide bonds played a pivotal role in inhibiting the thermal aggregation, considered by Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE), multiplies spectroscopy, and analysis of dynamic exchange of sulfhydryl-disulfide bonds. Meanwhile, the oxidation of exposed hydrophobic sites due to plasma treatment resulted in the transformation of the OVA molecule's surface from hydrophobic to hydrophilic, contributing significantly to the aggregation inhibition. Additionally, compared to an untreated sample of OVA, almost one-fold increase in emulsifying ability (EAI) and 1.5-fold in emulsifying stability (ESI) was observed after 4 min of plasma treatment. These findings demonstrated that plasma treatment not only enhanced the thermal stability of OVA, but also improved its emulsification properties.

Different Methods to Modify the Hydrophilicity of Titanium Implants with Biomimetic Surface Topography to Induce Variable Responses in Bone Marrow Stromal Cells.

The osteoblastic differentiation of bone marrow stromal cells (bMSCs), critical to the osseointegration of titanium implants, is enhanced on titanium surfaces with biomimetic topography, and this is further enhanced when the surfaces are hydrophilic. This is a result of changing the surface free energy to change protein adsorption, improving cell attachment and differentiation, and improving bone-to-implant contact in patients. In this study, we examined different methods of plasma treatment, a well-accepted method of increasing hydrophilicity, and evaluated changes in surface properties as well as the response of bMSCs in vitro. Commercially pure Ti and titanium-aluminum-vanadium (Ti6Al4V) disks were sand-blasted and acid-etched to impart microscale and nanoscale roughness, followed by treatment with various post-processing surface modification methods, including ultraviolet light (UV), dielectric barrier discharge (DBD)-generated plasma, and plasma treatment under an argon or oxygen atmosphere. Surface wettability was based on a sessile water drop measurement of contact angle; the elemental composition was analyzed using XPS, and changes in topography were characterized using scanning electron microscopy (SEM) and confocal imaging. The cell response was evaluated using bMSCs; outcome measures included the production of osteogenic markers, paracrine signaling factors, and immunomodulatory cytokines. All plasma treatments were effective in inducing superhydrophilic surfaces. Small but significant increases in surface roughness were observed following UV, DBD and argon plasma treatment. No other modifications to surface topography were noted. However, the relative composition of Ti, O, and C varied with the treatment method. The cell response to these hydrophilic surfaces depended on the plasma treatment method used. DBD plasma treatment significantly enhanced the osteogenic response of the bMSCs. In contrast, the bMSC response to argon plasma-treated surfaces was varied, with an increase in OPG production but a decrease in OCN production. These results indicate that post-packaging methods that increased hydrophilicity as measured by contact angle did not change the surface free energy in the same way, and accordingly, cells responded differently. Wettability and surface chemistry alone are not enough to declare whether an implant has an improved osteogenic effect and do not fully explain how surface free energy affects cell response.

The effect of dielectric barrier discharge plasma treatment on Dulcicalothrix alborzica (Nostocales, cyanobacteria) under lead stress

Cyanobacteria have shown considerable potential as effective adsorbents for the elimination of trace metals. Nevertheless, the precise adsorption mechanism of Dulcicalothrix alborzica remains uncertain. In this study, the activated water and biomass from Dulcicalothrix alborzica under dielectric barrier discharge plasma (DBD) treatment for lead removal were investigated at 5 (P5), 10 (P10), 15 (P15), and 20 (P20) minutes. Also, the FTIR and GC-MS analyses for identifying the functional groups and chemical composition of the heavy metal adsorption were performed. The results of lead removal in activated water and biomass under DBD treatment showed that the highest level of metal removal belonged to P20 and P15 at 90 min, respectively. The FTIR analysis showed that all three FTIR spectra of the control sample, activated water, and activated biomass with cold plasma, in terms of the intensity and the wave number, matched to a great extent. In addition, the GC-MS test showed that the 3-methylbutanal and 2-methylbutanal were the predominant volatile compounds detected across all experimental treatments. The general result showed that compared to activated biomass and water, activated water with atmospheric cold plasma had a greater ability to remove lead heavy metal (173.4 ± 1.77 g dry weight). Moreover, a longer time (P20) to let the reactive species work on the substance is recommended for future investigation. Further studies are necessary to improve the efficacy of heavy metal removal from liquid matrices, identify the suitable voltage and retention period, and distinguish the appropriate mechanism of metal removal from liquid matrices in order to stay safe from metal toxicity from consumption.

Surface activation of viscose textiles via air, argon, and oxygen dielectric barrier discharge plasma: Influence of peak voltage

Abstract This paper discusses the use of atmospheric pressure dielectric barrier discharge (DBD) plasma treatment to enhance the surface qualities of viscose fabrics. The study explores the effects of different plasma gases, discharge voltages, and exposure times on the treated fabrics. The findings emphasize the importance of optimizing the plasma's peak voltage to achieve desired surface treatment outcomes. The document also presents data on color strength, wettability, color fastness, and tensile strength of the treated fabrics, as well as SEM analysis of surface morphology and chemical analysis using FTIR and EDX. The results show that treatment at a peak voltage of 11.83 kV is more efficient, except for the tensile strength which is enhanced at a peak voltage of 8.92 kV. The oxygen plasma treatment significantly improves the color strength, which exhibits an increase from 11 to 18. The intensified color was attributed to the significant influence of electrostatic interactions between the charged hydroxyl groups of the oxygen plasma treated viscose textiles and the dye molecules, which enhance the printability. The oxygen dielectric barrier discharge plasma exhibits a higher ability to enhance the properties of textiles when compared to air and argon plasmas. This study presents a sustainable, economical, secure, and ecologically friendly approach to explore new fabrics for specific uses.

Effect of DBD Plasma Treatment on Activity of Mo-Based Sulfur-Resistant Methanation Catalyst.

By combining the advantages of dielectric barrier discharge (DBD) low temperature plasma and fluidized bed, the effect of plasma on the performance of supported Mo-based catalyst was studied in this paper. The performance of the catalyst obtained by plasma treatment, calcined, plasma+calcined was compared, and the appropriate catalyst preparation scheme was explored. Comparing with the three catalysts, it was concluded that the catalyst average conversion after 30 W plasma treatment is 33.40 %, which was 8.94 % and 12.75 % higher than the other two, respectively. The structure and properties of the catalyst were characterized by N2-Physisorption, H2-chemisorption, XRD, TEM, XPS, Raman and NO-pulse adsorption. Then, by analyzing the characterization results, it can be seen that plasma can make the catalyst have a higher specific surface area and a more dispersed active metal with smaller grain size. Through the surface species identification characterization, it was found that plasma can produce more defective structures and expose more active sites, which is the main reason for the difference in conversion.

Effects of moderate dielectric barrier discharge (DBD) plasma treatment on the structure, antigenicity, and digestibility of casein

Casein is the primary allergen in the dairy products. This study investigated the effects of moderate dielectric barrier discharge (DBD) plasma treatment on the structure, antigenicity, and digestibility of casein. The results showed that exposure to moderate DBD plasma for 4 min decreased the antigenicity, digestibility, total amino acid content, α-helix content, surface hydrophobicity, and total free sulfhydryl (SH) groups of casein by 18.2%, 9.5%, 42.2%, 4.5%, 51.0%, and 50.9%, respectively. The amino acid side chains of casein were oxidized, but cleavage was not observed on the peptide bone. Moderate DBD plasma treatment induced structural modification and oxidation of the amino acid side chains, which disrupted both the conformational and linear epitopes of casein, resulting in a reduction of its antigenicity. The modification of amino acid may have also disrupted the enzymatic cleavage site of casein, leading to a decrease in its digestibility. This study provides evidence that moderate DBD plasma treatment can decrease the antigenicity of casein, potentially broadening the application of dairy products in the food industry.

Investigation into potential allergenicity of DBD plasma-treated casein digestion products based on immunoglobulin E linear epitopes and the sensitized-cell model

The study aimed to investigate the allergenicity change in casein treated with dielectric barrier discharge (DBD) plasma during in vitro simulated digestion, focusing on the immunoglobulin E (IgE) linear epitopes and utilizing a sensitized-cell model. Results indicated that prior treatment with DBD plasma treatment (4 min) before simulated digestion led to a 10.5% reduction in the IgE-binding capacity of casein digestion products. Moreover, the release of biologically active substances induced from KU812 cells, including β-HEX release rate, human histamine, IL-4, IL-6, and TNF-α, decreased by 2.1, 28.1, 20.6, 11.6, and 17.3%, respectively. Through a combined analysis of LC-MS/MS and immunoinformatics tools, it was revealed that DBD plasma treatment promoted the degradation of the IgE linear epitopes of casein during digestion, particularly those located in the α-helix region of αs1-CN and αs2-CN. These findings suggest that DBD plasma treatment prior to digestion may alleviate casein allergic reactions.

Reduction of antigenicity and emulsibility improvement of ovalbumin by dielectric-barrier discharge plasma treatment induced structure modification

The effects of Dielectric-Barrier Discharge (DBD) plasma treatment (40 kV, 1–4 min) on the structure, antigenicity and emulsibility of ovalbumin (OVA) were investigated. Plasma-induced structural changes of OVA were determined by SDS-PAGE, multi-spectroscopic, and LC-MS/MS analysis. Meanwhile, the reduction in antigenicity of OVA was evaluated by western blotting (WB) and enzyme-linked immunosorbent assay (ELISA) analysis. The results indicated effective elimination of the antigenicity of OVA was achieved after 4 min of plasma treatment. The immunoglobulin E (IgE) binding capacity of OVA was notably reduced by 90.80%, as evidenced by WB and ELISA analysis. Plasma-mediated oxidation led to the unfolding of OVA's structure, resulting in alterations to its conformational epitope, and the partial destruction of linear epitopes through polypeptide chain cleavage, thus contributing to the reduction in antigenicity. These findings were supported by the results of SDS-PAGE, multi-spectroscopic, and LC-MS/MS analysis. Furthermore, a significant increase (53%) in emulsifying ability and a one-fold improvement in emulsifying stability of OVA were achieved after 4 min of plasma treatment. The current study confirms that DBD plasma treatment not only reduces the allergenicity of OVA but also enhance its emulsibility through structural modification.

Effect of atmospheric dielectric barrier discharge treatment on the triboelectric charging properties of brominated Polyethylene granules

This paper aims to investigate the effect of dielectric barrier discharge (DBD) plasma treatment on the triboelectric charging properties of granular materials containing brominated flame retardants (BFRs). This work focuses on the impact of treatment time and the applied voltage frequency. Experiments were carried out on Polyethylene (PE) particles containing 40000 ppm of bromine (PE 4.6 % of Hexabromobenzene) and BFR-free PE. The DBD treated particles were then charged by triboelectric effect in a multi-cylinder device. The triboelectric charge acquired by each sample was quantified using a Faraday cage connected to an electrometer. The humidity of the ambient air ranged between 51 % and 60 % and the temperature varied from 16.5 °C to 19 °C during the experiments. Results show the significant influence of DBD treatment time on the triboelectric charging of brominated and non-brominated PE granules. In case of brominated PE, the particles acquire less charge than the non-brominated ones. Furthermore, it was found that the charge of DBD-treated particles is influenced by the applied voltage frequency. The observed variation in triboelectric behavior may be attributed to the changes in the roughness and wettability of the polymer surface caused by DBD.

Atmospheric–pressure DBD plasma modifying photoemission, optical and electrical properties of polycarbonate films

In this study, the DBD plasma reactor has been constructed, characterized, and tested to be employed in material treatment for use in different applications. A neon power source with an output of 10 kV, 30 mA, with a frequency of 20 kHz is used to drive the DBD reactor in an atmospheric-pressure environment. The investigation covered the analysis of many parameters of the dielectric barrier discharge (DBD) reactor, including its discharge voltage, current, capacitance, consumption energy, and the light emission of the produced plasma. Also, to examine the generated DBD plasma effect, the photoemission, optical, and electrical characteristics of untreated/treated polycarbonate films were investigated using photoluminescence spectroscopy, UV/Vis spectroscopy, and electrical spectroscopy. The results demonstrated the appearance of two modes in the DBD discharge: filamentary and homogeneous. Moreover, the DBD reactor's power consumption has been measured to be 20 mW at a supplied voltage of 6.5 kV peak-to-peak, operated in atmospheric–pressure. The photoluminescence emission results emphasized that the treated films are modified particularly with increasing DBD treatment time. The UV–Vis spectra demonstrated a notable displacement of the absorption edge towards higher wavelengths as the duration of DBD exposure increased. This is indicative of the reduction of the band gap energy, thus improving the electric conductivities. The optical parameters of the treated polycarbonate films were enhanced in comparison to the untreated sample. Through the used frequency range, measurements of dielectric loss, dielectric constant, as well as AC electrical conductivity, are sensitive parameters to the modifications in electrical behaviors due to DBD plasma treatment.

NH3 plasma synthesis of amino modified NiCo layered double hydroxide nanoflowers for carbon dioxide photoreduction

Photoreduction as the paramount ingredient of CO2 catalytic conversion plays an eminent role in greenhouse gas treatment. As a promising catalyst, layered double hydroxide has been widely studied because of its rich variety, low hazard and easy availability. In an effort to improve the productivity of photocatalytic CO2 reduction, the preparation of efficient photocatalysts becomes the key to solve this challenge. Thin nickel-cobalt bimetallic hydroxides (NiCo LDH) were prepared by the hydrothermal method of glycerol and methanol. Amino groups were grafting onto NiCo LDH nanosheets in an ammonia atmosphere by low-temperature plasma. The photocatalytic reduction performance of NH2-NiCo LDH was optimized by adjusting the time of plate dielectric barrier discharge plasma treatment. This work provides theoretical basics for modification of layered double hydroxide.

Insights on dielectric barrier discharge plasma treatment of oil drilling cuttings

Oil drilling cuttings produced during oil exploration and extraction contain a high percentage of crude oil, ranging from 5% to 20% weight ratio (w/w) on a dry basis, and must be managed and treated properly before their release to the environment. In this study, non-thermal plasma (NTP) was investigated as an advanced oxidation process for the efficient, sustainable and cost-effective treatment of oil drilling cuttings. To this end, a plane-to-grid dielectric barrier discharge (DBD) reactor operating at atmospheric pressure was tested under different plasma conditions. The effect of treatment time, DBD power and air flow rate on the total organic carbon (TOC) removal efficiency was assessed and the energy efficiency of the process was determined. Within 10 min of plasma treatment, a very high TOC and total petroleum hydrocarbons (TPH) removal (∼90% and ∼99%, respectively) was achieved, while polycyclic aromatic hydrocarbons (PAHs) were degraded by ∼50% within 2 min of treatment. Depending on the experimental conditions, the energy efficiency of the process varied from 5 to 35 mg/kJ. From GC-MS analysis, several byproducts of the oxidation of oil drilling cuttings were identified, while the analysis of exhaust gases revealed that ∼85.1% of the removed organics from oil drilling cuttings was transformed to CO2 and CO. This study provides critical information on the effectiveness of the NTP process for the treatment of heavily contaminated solid wastes and can be considered as the critical step for its application for the treatment of solid wastes from the oil industry.

Germination, Physicochemical Properties, and Antioxidant Enzyme Activities in Kangkong (Ipomoea aquatica Forssk.) Seeds as Affected by Dielectric Barrier Discharge Plasma

Dielectric barrier discharge (DBD) plasma has been utilized as a sustainable technology to enhance seed germination in various plant species. The objective of this research was to identify the mechanism of physicochemical properties and antioxidant enzyme activities to promote kangkong (Ipomoea aquatica Forssk.) seed germination using different durations of DBD plasma treatments. Seeds were exposed to atmospheric DBD plasma from 5 to 20 min, compared to non-treated seeds as the control. According to SEM images, the seed surface had cracks and grew wider as a result of the prolonged DBD plasma treatments. A longer DBD plasma treatment exhibited a lower water contact angle and increased water absorption. DBD plasma treatments strongly improved germination percentages and hydrogen peroxide (H2O2) contents. Seeds treated with DBD plasma for 20 min showed the highest malondialdehyde (MDA) content and the lowest field emergence. Catalase (CAT) activity increased under DBD plasma treatments for 5 and 10 min. Ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities were not statistically different among the treatments. This finding suggested that DBD plasma treatments stimulated the germination of kangkong seeds by modifying the seed surface, and upregulating H2O2 content and CAT activity. Five minutes was an appropriate time to treat DBD plasma.

Cold Plasma for Preparation of Pd/graphene Catalysts toward 4-nitrophenol Reduction: Insight into Plasma Treatment

Objective: Controllable synthesis of high-performance palladium catalysts toward 4-nitrophenol (4-NP) reduction still remains a significant challenge. This work aims to exploit a facile dielectric barrier discharge (DBD) plasma treatment method to synthesize the graphene-supported palladium catalysts (Pd/G-P), and to as certain the effect of plasma discharge voltage and discharge time on the structure-performance relationship of Pd/G-P, then provides insight into the synthesis of high-performance Pd/G-P by DBD plasma. Methods: A graphene-supported palladium precursor was prepared by excess impregnation method firstly, and then treated using hydrogen DBD plasma to synthesize Pd/G-P catalysts. The effect of discharge voltage and discharge time on the structure-performance relationship of Pd/G-P were systematically investigated based on the reaction model of 4-NP reduction. Results: The Pd/G-P prepared by DBD plasma at discharge voltage of 13.0kV and discharge time of 4min exhibited the highest performance for 4-NP reduction with a rate constant (k) of as high as 0.88min-1. The discharge diagnosis and sample characterization results showed that Pd/G-P with much higher than Pd/C and O/C atomic ratios, and surface defects density can be obtained at the optimal discharge parameters. These features enabled the formation of small-sized and highly-dispersed palladium nanoparticles, thereby enhancing the catalytic activity. The experimental study of reaction kinetics showed that plasma synthesized Pd/G-P at optimal parameters can adsorb intermediate reactants more effectively and enhance the catalytic performance. Conclusion: In this work, controllable synthesis of high-performance Pd/G-P were synthesized, which provides important reference significance for preparing other catalysts by plasma regulation.

Characterization of Molecular Interactions in the Bondline of Composites from Plasma-Treated Aluminum and Wood.

Wood and aluminum composites are becoming increasingly attractive due to their ability to combine the advantages of both materials: the lightweight nature of wood and the strength of aluminum. However, using conventional wood adhesives like polyvinyl acetate (PVAc) to bond these dissimilar materials is challenging and requires special surface treatments. Prior studies have demonstrated that applying a dielectric barrier discharge plasma treatment significantly enhances shear and bending strengths in beech wood/aluminum bonds. This study focuses on the molecular interactions between PVAc and aluminum or beech wood influenced by plasma surface modification. Surface-sensitive methods, including X-ray photoelectron spectroscopy, infrared reflection adsorption spectroscopy and atomic force microscopy, were employed to characterize the PVAc films on the corresponding surfaces and to identify possible interactions. The ultrathin PVAc films required for this purpose were deposited by spin coating on untreated and plasma-treated aluminum. The aluminum surface was cleaned and oxidized by plasma. Additionally, hydroxyl species could be detected on the surface. This can lead to the formation of hydrogen bonds between the aluminum and the carbonyl oxygen of PVAc after plasma treatment, presumably resulting in increased bond strength. Furthermore, the beech wood surface is activated with polar oxygen species.

Effects of dielectric barrier discharge plasma modification on structure, physicochemical and functional properties of watermelon peel pectin

Dielectric barrier discharge (DBD) plasma is a simple and green method for biomacromolecule modification, and watermelon peel pectin (WMP) has broad application prospect in food industry. This study investigated the effects of DBD plasma under different voltage (20 V, 40 V) and treatment time (1 min, 3 min, 5 min) on the structural, physicochemical and functional properties of WMP. The DBD plasma treatment (40 V, 5 min) exhibited the lowest molecular weight (Mw, 199.06 ± 8.05 kg/mol), average molecular weight (Mn, 27.15 ± 1.75 kg/mol), degree of methylation (DM, 36.18 ± 0.65%) and acetylation (DA, 2.33 ± 0.09%) of WMP. Moreover, DBD plasma treatment could degrade the main chain of WMP, and had less effect on the side chain. The microstructure of WMP changes from dense block structures to porous and thin fibrous, while pectin molecules are degraded and oxidized after DBD plasma treatment. Compared with the native WMP, DBD plasma treatment at different modes effectively increased the thermal stability, antioxidant ability, solubility and emulsifying properties of WMP, but lowered its shear thinning fluid behavior and liquid-like property. Conclusively, our results show that DBD plasma is a promising way to modified and improve functional properties of WMP.