Cold plasma is an emerging technology offering many potential applications for food packaging. Wh... more Cold plasma is an emerging technology offering many potential applications for food packaging. While it was originally developed to increase the surface energy of polymers, enhancing their adhesion and printability, it has recently emerged as a powerful tool for surface sterilisation of both food and food packaging materials. The food packaging industry is still dominated by petroleum derived polymers but in the past few decades there has been significant interest in the development of environment friendly, biodegradable green polymers. In this study, the interaction and effects of cold plasma with biopolymer based packaging materials (polylactic acid, zein, sodium caseinate, starch, chitosan and gelatin) and its potential for active and intelligent packaging was investigated. DBD (Dielectric Barrier Discharge) plasma increased the surface roughness of all the treated polymers films. DBD plasma treatments did not induce significant changes in the thermal profile of the polymers, but significant increases in the initial degradation temperature and maximum degradation temperature was observed for poly(lactic acid) and starch. DBD plasma also increased the equilibrium moisture content of both protein films: zein and sodium caseinate, but no significant increases in the water vapour and oxygen permeability was noticed for any of the films. An increase in overall migration was observed in PLA for various food simulants however they were below the EU regulatory limits. Plasma treatment increased the polar component of the total surface energy of all the polymers. The increase in the O/C atomic ratio shows the formation of new oxygen-containing polar groups on the film surface of the plasma treated films. Plasma treatments of both zein and sodium caseinate film lead to a change in the I would also like to thank my friends and colleagues especially Misra, Shekhar, Yash, Chaitu, Lu, Dana, Caitlin, Apurva, Kompal, Daniela and Raquel for all the laughs we have shared, the distraction was indispensible. Finally, I would like to thank my parents, sister and fiancée for their constant encouragement and support throughout my work without which none of this would have been possible.
Cold plasma is a novel technology that has shown potential for food decontamination, shelf life e... more Cold plasma is a novel technology that has shown potential for food decontamination, shelf life extension, and processing of heat-sensitive food products. The application of cold plasma in fruit juice processing is an innovative approach for safety and quality retention of fruit juices with potential commercial prospects. Cold plasma has proven its efficacy in inactivating various pathogenic and spoilage organisms found in fruit juices. The simple design, low cost, easy scale-up, flexible configuration and environment-friendly nature of cold plasma offers unique advantages over traditional processing technologies. However, cold plasma food processing is still in its nascent form, and needs further research to assess its application on a wide range of fruit juices and optimization of process variables.
High voltage atmospheric cold plasma is a novel, environment-friendly technology which has gained... more High voltage atmospheric cold plasma is a novel, environment-friendly technology which has gained significant attention in the recent decades. It has shown promising results for surface modification and decontamination. The aim of this study was to determine the effects of high voltage atmospheric plasma treatment at 80 kV for 5 minutes on starch films of different origins (rice, potato, tapioca, corn) with varying amylose content. Cold plasma treatment resulted in an increase in glass transition temperature, surface roughness and surface oxygenation for all the films. Rice starch films with low amylose content were found to be most susceptible whereas corn starch films with high amylose content showed the least changes in the physical or chemical properties after cold plasma treatments. The results clearly indicate that amylose content and the starch source plays an important role in determining its interaction with cold plasma.
Cold plasma (CP) technology has proven very effective as an alternative tool for food decontamina... more Cold plasma (CP) technology has proven very effective as an alternative tool for food decontamination and shelf-life extension. The impact of CP on food quality is very crucial for its acceptance as an alternative food processing technology. Due to the non-thermal nature, CP treatments have shown no or minimal impacts on the physical, chemical, nutritional and sensory attributes of various products. This review also discusses the negative impacts and limitations posed by CP technology for food products. The limited studies on interactions of CP species with food components at the molecular level offers future research opportunities. It also highlights the need for optimization studies to mitigate the negative impacts on visual, chemical, nutritional and functional properties of food products. The design versatility, non-thermal, economical and environmentally friendly nature of CP offers unique advantages over traditional processing technologies. However, CP processing is still in i...
Dielectric barrier discharge atmospheric plasma is a novel non-thermal technology for the food an... more Dielectric barrier discharge atmospheric plasma is a novel non-thermal technology for the food and packaging industry. The effects of dielectric barrier discharge plasma on the surface, structural, thermal and moisture sorption properties of edible zein films have been examined.
The effects of dielectric barrier discharge plasma treatment on zein film containing thymol as an... more The effects of dielectric barrier discharge plasma treatment on zein film containing thymol as an active ingredient were evaluated. The plasma discharge was optically characterized to identify the reactive species. A significant increase in the film roughness (p < 0.05) was observed due to the etching effect of DBD plasma, which was correlated with the increase in the diffusion rate of thymol in the food simulant. The diffusion of thymol from the zein film was measured in aqueous solution. The kinetics of thymol release followed the Fick's law of diffusion as shown by the high correlation coefficients between experimental and theoretical data. No significant change (p > 0.05) was observed for the thermal properties of the antimicrobial films after DBD plasma treatment.
Dielectric barrier discharge (DBD) air plasma is a novel technique for in-package decontamination... more Dielectric barrier discharge (DBD) air plasma is a novel technique for in-package decontamination of food, but it has not been yet applied to the packaging material. Characterization of commercial polylactic acid (PLA) films was done after in-package DBD plasma treatment at different voltages and treatment times to evaluate its suitability as food packaging material. DBD plasma increased the roughness of PLA film mainly at the site in contact with high voltage electrode at both the voltage levels of 70 and 80 kV. DBD plasma treatments did not induce any change in the glass transition temperature, but significant increase in the initial degradation temperature and maximum degradation temperature was observed. DBD plasma treatment did not adversely affect the oxygen and water vapor permeability of PLA. A very limited overall migration was observed in different food simulants and was much below the regulatory limits. Industrial relevance: In-package DBD plasma is a novel and innovative approach for the decontamination of foods with potential industrial application. This paper assesses the suitability of PLA as food packaging material for cold plasma treatment. It characterizes the effect of DBD plasma on the packaging material when used for in-package decontamination of food. The work described in this research offers a promising alternative to classical methods used in fruit and vegetable industries where in-package DBD plasma can serve as an effective decontamination process and avoids any post-process recontamination or hazards from the package itself.
Logistic model was found ideal for describing the kinetics of POD inactivation, as evident from... more Logistic model was found ideal for describing the kinetics of POD inactivation, as evident from RMSE values. The active species of plasma viz. ROS, RNS, UV and metastable species probably cause protein denaturation by side chain modification, leading to inactivation.
Sodium caseinate films were physico-chemically characterized for the effects of atmospheric diele... more Sodium caseinate films were physico-chemically characterized for the effects of atmospheric dielectric barrier discharge (DBD) plasma as function of applied voltage and treatment times.
The application of nonthermal dielectric barrier discharge (DBD) plasma for altering the hydrophi... more The application of nonthermal dielectric barrier discharge (DBD) plasma for altering the hydrophilicity or hydrophobicity of polymer surfaces is well known. In this work, we demonstrate the potential of DBD plasma in enhancing the surface hydrophobicity of freshly baked biscuits, evident from the increased spread area of vegetable oil. The electrical and optical characteristics of the DBD plasma source have also been described. The spread area of individual oil drops has been measured using a digital image analysis technique. An exponential order of increase in the spread area has been observed at 80 kV with respect to treatment time, following DBD treatment. The findings reported in this work have applications in the industrial preparation of biscuit and cracker variants, where post-baking oil spray is desired. The effect of plasma treatments on the chemical constituents of biscuit requires further investigation. Industrial relevance: There is a substantive evidence for the need of an alternate process which allows retaining functionality of sprayed oil in biscuits, with less oil or fat and increased spread. A novel process based on barrier discharge atmospheric pressure nonthermal plasma for enhancement of oil spreadability on dry, snack food products is developed. For a given volume of oil, up to 50% more spreading of oil can be achieved within few seconds of the process as compared to currently used methods. The plasma source can be easily integrated into a continuous biscuit and cracker production or finishing line.
Atmospheric cold plasmas (ACPs) have received increased attention in recent years as a novel deco... more Atmospheric cold plasmas (ACPs) have received increased attention in recent years as a novel decontamination technology in food and biological sciences research. Cold plasma treatment is especially desirable in food industries for in-package decontamination as it prevents postprocessing contamination. ACPs are often obtained using noble gases or air. This work reports the decontamination of strawberries inside a sealed package with two different gas mixtures, viz. 65 % O 2 +16 % N 2 +19 % CO 2 and 90 % N 2 + 10 % O 2 . The electrical parameters of the dielectric barrier discharge obtained at 60 kV rms (50 Hz) applied voltage over a 40-mm gap have been characterised using capacitive (charge-voltage) measurements and show for each gas mixture an increase in transferred power and charge in the presence of the fresh produce. The background micro-flora of the strawberries was reduced by an average of~3.0 log cycles from the initial levels of 5 log 10 CFU/g in 300 s of in-package ACP discharge. Plasma treatments with the two gas mixtures showed similar effects on microbial reduction levels. Strawberries treated and stored in a high oxygen gas mixture showed favourable quality results with similar respiration rates and an 11 % higher firmness than the control stored for 24 h.
Cold plasma is an emerging technology offering many potential applications for food packaging. Wh... more Cold plasma is an emerging technology offering many potential applications for food packaging. While it was originally developed to increase the surface energy of polymers, enhancing their adhesion and printability, it has recently emerged as a powerful tool for surface sterilisation of both food and food packaging materials. The food packaging industry is still dominated by petroleum derived polymers but in the past few decades there has been significant interest in the development of environment friendly, biodegradable green polymers. In this study, the interaction and effects of cold plasma with biopolymer based packaging materials (polylactic acid, zein, sodium caseinate, starch, chitosan and gelatin) and its potential for active and intelligent packaging was investigated. DBD (Dielectric Barrier Discharge) plasma increased the surface roughness of all the treated polymers films. DBD plasma treatments did not induce significant changes in the thermal profile of the polymers, but significant increases in the initial degradation temperature and maximum degradation temperature was observed for poly(lactic acid) and starch. DBD plasma also increased the equilibrium moisture content of both protein films: zein and sodium caseinate, but no significant increases in the water vapour and oxygen permeability was noticed for any of the films. An increase in overall migration was observed in PLA for various food simulants however they were below the EU regulatory limits. Plasma treatment increased the polar component of the total surface energy of all the polymers. The increase in the O/C atomic ratio shows the formation of new oxygen-containing polar groups on the film surface of the plasma treated films. Plasma treatments of both zein and sodium caseinate film lead to a change in the I would also like to thank my friends and colleagues especially Misra, Shekhar, Yash, Chaitu, Lu, Dana, Caitlin, Apurva, Kompal, Daniela and Raquel for all the laughs we have shared, the distraction was indispensible. Finally, I would like to thank my parents, sister and fiancée for their constant encouragement and support throughout my work without which none of this would have been possible.
Cold plasma is a novel technology that has shown potential for food decontamination, shelf life e... more Cold plasma is a novel technology that has shown potential for food decontamination, shelf life extension, and processing of heat-sensitive food products. The application of cold plasma in fruit juice processing is an innovative approach for safety and quality retention of fruit juices with potential commercial prospects. Cold plasma has proven its efficacy in inactivating various pathogenic and spoilage organisms found in fruit juices. The simple design, low cost, easy scale-up, flexible configuration and environment-friendly nature of cold plasma offers unique advantages over traditional processing technologies. However, cold plasma food processing is still in its nascent form, and needs further research to assess its application on a wide range of fruit juices and optimization of process variables.
High voltage atmospheric cold plasma is a novel, environment-friendly technology which has gained... more High voltage atmospheric cold plasma is a novel, environment-friendly technology which has gained significant attention in the recent decades. It has shown promising results for surface modification and decontamination. The aim of this study was to determine the effects of high voltage atmospheric plasma treatment at 80 kV for 5 minutes on starch films of different origins (rice, potato, tapioca, corn) with varying amylose content. Cold plasma treatment resulted in an increase in glass transition temperature, surface roughness and surface oxygenation for all the films. Rice starch films with low amylose content were found to be most susceptible whereas corn starch films with high amylose content showed the least changes in the physical or chemical properties after cold plasma treatments. The results clearly indicate that amylose content and the starch source plays an important role in determining its interaction with cold plasma.
Cold plasma (CP) technology has proven very effective as an alternative tool for food decontamina... more Cold plasma (CP) technology has proven very effective as an alternative tool for food decontamination and shelf-life extension. The impact of CP on food quality is very crucial for its acceptance as an alternative food processing technology. Due to the non-thermal nature, CP treatments have shown no or minimal impacts on the physical, chemical, nutritional and sensory attributes of various products. This review also discusses the negative impacts and limitations posed by CP technology for food products. The limited studies on interactions of CP species with food components at the molecular level offers future research opportunities. It also highlights the need for optimization studies to mitigate the negative impacts on visual, chemical, nutritional and functional properties of food products. The design versatility, non-thermal, economical and environmentally friendly nature of CP offers unique advantages over traditional processing technologies. However, CP processing is still in i...
Dielectric barrier discharge atmospheric plasma is a novel non-thermal technology for the food an... more Dielectric barrier discharge atmospheric plasma is a novel non-thermal technology for the food and packaging industry. The effects of dielectric barrier discharge plasma on the surface, structural, thermal and moisture sorption properties of edible zein films have been examined.
The effects of dielectric barrier discharge plasma treatment on zein film containing thymol as an... more The effects of dielectric barrier discharge plasma treatment on zein film containing thymol as an active ingredient were evaluated. The plasma discharge was optically characterized to identify the reactive species. A significant increase in the film roughness (p < 0.05) was observed due to the etching effect of DBD plasma, which was correlated with the increase in the diffusion rate of thymol in the food simulant. The diffusion of thymol from the zein film was measured in aqueous solution. The kinetics of thymol release followed the Fick's law of diffusion as shown by the high correlation coefficients between experimental and theoretical data. No significant change (p > 0.05) was observed for the thermal properties of the antimicrobial films after DBD plasma treatment.
Dielectric barrier discharge (DBD) air plasma is a novel technique for in-package decontamination... more Dielectric barrier discharge (DBD) air plasma is a novel technique for in-package decontamination of food, but it has not been yet applied to the packaging material. Characterization of commercial polylactic acid (PLA) films was done after in-package DBD plasma treatment at different voltages and treatment times to evaluate its suitability as food packaging material. DBD plasma increased the roughness of PLA film mainly at the site in contact with high voltage electrode at both the voltage levels of 70 and 80 kV. DBD plasma treatments did not induce any change in the glass transition temperature, but significant increase in the initial degradation temperature and maximum degradation temperature was observed. DBD plasma treatment did not adversely affect the oxygen and water vapor permeability of PLA. A very limited overall migration was observed in different food simulants and was much below the regulatory limits. Industrial relevance: In-package DBD plasma is a novel and innovative approach for the decontamination of foods with potential industrial application. This paper assesses the suitability of PLA as food packaging material for cold plasma treatment. It characterizes the effect of DBD plasma on the packaging material when used for in-package decontamination of food. The work described in this research offers a promising alternative to classical methods used in fruit and vegetable industries where in-package DBD plasma can serve as an effective decontamination process and avoids any post-process recontamination or hazards from the package itself.
Logistic model was found ideal for describing the kinetics of POD inactivation, as evident from... more Logistic model was found ideal for describing the kinetics of POD inactivation, as evident from RMSE values. The active species of plasma viz. ROS, RNS, UV and metastable species probably cause protein denaturation by side chain modification, leading to inactivation.
Sodium caseinate films were physico-chemically characterized for the effects of atmospheric diele... more Sodium caseinate films were physico-chemically characterized for the effects of atmospheric dielectric barrier discharge (DBD) plasma as function of applied voltage and treatment times.
The application of nonthermal dielectric barrier discharge (DBD) plasma for altering the hydrophi... more The application of nonthermal dielectric barrier discharge (DBD) plasma for altering the hydrophilicity or hydrophobicity of polymer surfaces is well known. In this work, we demonstrate the potential of DBD plasma in enhancing the surface hydrophobicity of freshly baked biscuits, evident from the increased spread area of vegetable oil. The electrical and optical characteristics of the DBD plasma source have also been described. The spread area of individual oil drops has been measured using a digital image analysis technique. An exponential order of increase in the spread area has been observed at 80 kV with respect to treatment time, following DBD treatment. The findings reported in this work have applications in the industrial preparation of biscuit and cracker variants, where post-baking oil spray is desired. The effect of plasma treatments on the chemical constituents of biscuit requires further investigation. Industrial relevance: There is a substantive evidence for the need of an alternate process which allows retaining functionality of sprayed oil in biscuits, with less oil or fat and increased spread. A novel process based on barrier discharge atmospheric pressure nonthermal plasma for enhancement of oil spreadability on dry, snack food products is developed. For a given volume of oil, up to 50% more spreading of oil can be achieved within few seconds of the process as compared to currently used methods. The plasma source can be easily integrated into a continuous biscuit and cracker production or finishing line.
Atmospheric cold plasmas (ACPs) have received increased attention in recent years as a novel deco... more Atmospheric cold plasmas (ACPs) have received increased attention in recent years as a novel decontamination technology in food and biological sciences research. Cold plasma treatment is especially desirable in food industries for in-package decontamination as it prevents postprocessing contamination. ACPs are often obtained using noble gases or air. This work reports the decontamination of strawberries inside a sealed package with two different gas mixtures, viz. 65 % O 2 +16 % N 2 +19 % CO 2 and 90 % N 2 + 10 % O 2 . The electrical parameters of the dielectric barrier discharge obtained at 60 kV rms (50 Hz) applied voltage over a 40-mm gap have been characterised using capacitive (charge-voltage) measurements and show for each gas mixture an increase in transferred power and charge in the presence of the fresh produce. The background micro-flora of the strawberries was reduced by an average of~3.0 log cycles from the initial levels of 5 log 10 CFU/g in 300 s of in-package ACP discharge. Plasma treatments with the two gas mixtures showed similar effects on microbial reduction levels. Strawberries treated and stored in a high oxygen gas mixture showed favourable quality results with similar respiration rates and an 11 % higher firmness than the control stored for 24 h.
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