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Ng, Sing Wei
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Ng, Sing Wei
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Ng, Sing Wei
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Now showing 1 - 4 of 4
- PublicationAtmospheric Cold Plasma Interaction with Allergens in Food Processing(University College Dublin. School of Biosystems and Food Engineering, 2022)
; 0000-0002-2361-9557Approximately 5-15% of allergen recalls are associated with consumer reactions, which are largely attributed to cross contamination with allergens. Therefore, it is essential to mitigate against allergen cross-contamination during food processing, distribution and storage. Atmospheric Cold plasma (ACP) was found to effect functionality and modify proteins such as enzymes, owing to the chemical and bioactive radicals generated known collectively as reactive oxygen (ROS) and nitrogen species (RONS), together with physical stress such as electric field and UV irradiation. Allergens are comprised of proteins; thus, ACP was investigated as a promising tool to mitigate allergen cross-contamination in food processing sectors. The aim of this work is to understand and develop ACP based approaches for control and prevention of allergen cross-contamination within food processing. This program of research focused on developing a mechanistic understanding of how ACP interacts with food allergens and affects the antigenicity of food allergens. RSS systems, which comprised two modes of tunable plasma discharge, spark discharge (SD) and glow discharge (GD), were used as plasma source for the liquid application environment. To optimise the efficacy of application, diagnostics studies of the plasma devices and the chemical composition of plasma activated water (PAW) generated by RSS system were investigated. SDPAW predominantly contains H2O2 and NO3-. GDPAW predominantly contains peroxide, NO2- and NO3-. The concentration of ROS and RNS was dependent on applied voltage and frequency of the plasma. To understand the mechanism of plasma in gas-phase, the ignition and propagation of air discharges of SD and GD were examined using fast imaging diagnostic techniques in collaboration with the University of Liverpool. SD drives both anode-directed and cathode-directed streamers, while GD drives only anode directed streamers. SD had higher OH emission than GD at both positive and negative half-periods. The effect of SD and GD on the antigenicity reduction of milk-derived and wheat-derived allergens were then studied. Casein, a-lactalbumin and ß-lactoglobulin are the major allergens in bovine milk while gliadin is the major allergen in wheat gluten. These allergen solutions were treated directly by SD and GD. The antigenicity of caseins, a-lactalbumin and gliadin decreased while ß-lactoglobulin increased. The results showed the modification of chemical structure of plasma treated allergens. A concentration dependence also emerged across the different studies. For example, indirect PAW treatment reduced casein antigenicity but only at low concentrations of 0.01 mg/ml, when applied in combination with a mild heat treatment at 60 °C. The ROS generated in SDPAW is attributed to antigenicity reduction of casein, while RNS generated in either SDPAW or GDPAW was not involved. The mode of application was probed, where liquid mediated direct SD and GD RSS were compared with indirect PAW treatment, and further compared to direct gaseous dry plasma approaches of dielectric barrier discharge (DBD) in-package system and plasma brush (PB) system. The antigenicity reduction of milk-derived and wheat-derived allergens were studied in terms of sample concentrations and plasma process duration. The results showed the conformational and linear epitopes of plasma treated allergens were altered. The efficacy for antigenicity reduction is correlated with protein composition, sample concentration and plasma process duration. Overall, dry or liquid mediated plasma processes can be tailored to mitigate allergen residues in food processing. The food allergens from two important foods were investigated to reveal the universality of ACP. The effectiveness of antigenicity reduction was well explained by the modification of conformational and linear structures of allergens treated by ACP.8 - PublicationCharacterization of an atmospheric pressure air plasma device under different modes of operation and their impact on the liquid chemistry(AIP Publishing, 2021-03-29)
; ; ; ; ; It has been shown that plasma generated in contact with liquid can be tailored to tune the composition of plasma functionalized liquids. For biomedical applications, it is necessary to understand the generation of the plasma treated liquids to modulate the composition and thus the biological response. In this work, two distinct discharge compositions were realized by modifying the location of the ground electrode in a pin-to-liquid plasma system. Through this simple modification to the configurations, the spatiotemporal characteristics of the discharge were significantly affected which, in turn, affected the composition of the generated plasma activated water (PAW). Colorimetric testing of the PAW generated from each system revealed that only one configuration was able to generate PAW with a high concentration of H2O2. Using time-, space-, and wavelength-resolved imaging of excited plasma species [OH, N2 (SPS), N2+ (FNS), and atomic O], the differences in PAW composition were linked to the differences observed in the discharge dynamics between the two configurations.217Scopus© Citations 14 - PublicationDeposition of Cell Culture Coatings Using a Cold Plasma Deposition MethodCollagen coatings were applied onto polystyrene microplates using a cold atmospheric pressure plasma process. The coatings were compared to standard wet chemical collagen thin films using microscopy, surface energy, infra-red spectroscopy, electrophoresis, and cell culture techniques. Thin films were also deposited on gold electrodes using both coating methods and their structural and barrier properties probed using cyclic voltammetry. While the wet chemical technique produced a thicker deposit, both films appear equivalent in terms of coverage, porosity, structure, and chemistry. Significantly, the cold plasma method preserves both the primary and secondary structure of the protein and this results in high biocompatibility and cell activity that is at least equivalent to the standard wet chemical technique. The significance of these results is discussed in relation to the benefits of a single step plasma coating in comparison to the traditional multi-step aseptic coating technique.
Scopus© Citations 5 171 - PublicationThe effect of atmospheric cold plasma treatment on the antigenic properties of bovine milk casein and whey proteinsCasein, β-lactoglobulin and α-lactalbumin are major milk protein allergens. In the present study, the structural modifications and antigenic response of these bovine milk allergens as induced by non-thermal treatment by atmospheric cold plasma were investigated. Spark discharge (SD) and glow discharge (GD), as previously characterized cold plasma systems, were used for protein treatments. Casein, β-lactoglobulin and α-lactalbumin were analyzed before and after plasma treatment using SDS-PAGE, FTIR, UPLC-MS/MS and ELISA. SDS-PAGE results revealed a reduction in the casein and α-lactalbumin intensity bands after SD or GD treatments; however, the β-lactoglobulin intensity band remained unchanged. FTIR studies revealed alterations in protein secondary structure induced by plasma, particularly contents of β-sheet and β-turn. The UPLC-MS/MS results showed that the amino acid compositions decreased after plasma treatments. ELISA of casein and α-lactalbumin showed a decrease in antigenicity post plasma treatment, whereas ELISA of β-lactoglobulin showed an increase in antigenicity. The study indicates that atmospheric cold plasma can be tailored to mitigate the risk of bovine milk allergens in the dairy processing and ingredients sectors.
545Scopus© Citations 71