Plasma
Technology in Food Safety
Food
has long been associated with numerous food-borne diseases, whereas food safety
is a major concern for the food industries, regulatory bodies, and customers.
Pathogenic microorganisms are a major hassle concerning the food processing
industries, as they have an unfavorable impact on the health and economy of the
public, where processing techniques such as pasteurization, autoclaving,
canning, and steam sterilization are used to eliminate pathogenic microbes.
However, they possess several side effects, viz., nutritional loss, affect
sensory properties and degrade functional properties of the food. Thus, the food
industry continually strives for innovative technologies and approaches to
improve food production and processing methods as demand for raw or
non-heat-treated foods is increasing due to the preference of consumers for
healthy foods and improved consumer awareness.
Despite the competitive advantages of such innovations, the industry faces a global challenge of ensuring food security for a rapidly growing population due to the nature of the foods and the production methods that are prone to microbial and/or pest contaminations. Thus, the current food industry is focused on enhanced microbial food safety and quality without compromising the nutritional, functional, and sensory characteristics of foods, regardless of the difficulties or costs involved. Hence, the food industry relies on a range of intervention strategies, whereas processing steps are employed at points along the food chain to control contaminants to ensure both product safety and/or extend the shelf-life. The methods and technologies applied are to be the focus on most of the described factors while designing applications for novel tech applications.
One such emerging technology is plasma technology, which is a green processing technology that offers many potential applications and operates between most of the above requirements of the industry. Based on recent research and development data indicates that plasma processing has caught the interest of various areas of industry, including cereal, meat, poultry, dairy, fruits, vegetables, packaging, etc. as it helps to modify the food material for the desirable trait and maintains the nutritional and textural properties in addition to microbial decontamination. Thus, plasma technology can be used to improve microbial quality and prevent rapid physical, chemical, and sensory changes, which has shown that the process is effective in offering higher-quality products for consumption by extending the shelf life of foods.
The
plasma treatment is used for enhancing antimicrobial activity, structural
modification, decontamination of surfaces, and disinfection of food-processing
instruments. The treatment is more effective due to the combined hurdle effect
of CP with other emerging novel technologies such as nanotechnology
applications including nanofiber, nano-emulsion, nanoparticles,
and nano-encapsulation, and emerging non-thermal technologies, pulsed
electric field (PEF), pulsed light (PL), and ultra-sound processing on food or
food packaging materials to ensure food safety.
What is Plasma?
Plasma is referred to as the fourth state of matter, which is an ionized gas comprising several excited atomic, molecular, ionic, and radical species, co-existing with electrons, positive and negative ions, free radicals, gas atoms, molecules in the ground, or excited state, and quanta of electromagnetic radiation (UV photons and visible light).
The
plasma is classified as thermal or non-thermal plasma, whereas in thermal
plasmas, the ionization and chemical processes are mainly governed by the
temperature, which can reach more than 20,000 K. Thermal plasma systems are
used for applications requiring enormous heat, such as coating technology,
welding, cutting, and treatment of hazardous wastes. In non-thermal plasmas,
different temperatures can be achieved for different plasma species, mostly
around room temperature, which uses energy more efficiently to gain better
chemical selectivity. In non-thermal plasmas, the electron temperature governs
ionization and chemical processes, where plasma is in a metastable state with a
roughly zero net electrical charge.
Only non-thermal plasma is applied to food products. Cold plasma can be generated in gases like helium, argonium, oxygen, nitrogen, and a mixture of these gases. Non-thermal plasma can be formed by electrical, microwave, and radiofrequency power sources that generate a high electrical potential difference between two or more electrodes. There is an increased interest in atmospheric pressure cold plasma technologies in food applications because they do not require vacuum systems and enable continuous material processing.
The
plasma consists of an ionized gas comprising several excited atomic, molecular,
ionic, and radical species, co-existing with electrons, positive and negative
ions, free radicals, and gas atoms, molecules in the ground or excited state,
and quanta of electromagnetic radiation (UV photons and visible light). The
reactive species generated during plasma application depend on the gas and
operating conditions applied.
Helium and argonium plasma generate plasma species that do not react with many bioactive compounds and are mainly used for sanitization. The cold plasma on food consisted primarily of applying jet plasma using helium and argonium, which produced reactive species that are mainly inert to the chemical compounds present in food. These inert gases, and inert plasma, induced minimal chemical changes on the main food constituents, where cold plasma does not alter the food quality while being very efficient in sanitizing it. Later application of cold plasma migrated to the use of nitrogen, air, and modified atmosphere. Hence, air plasma is a potent source of reactive oxygen species (ROS) and reactive nitrogen species (RNS), which tend to react when in contact with living cells or with organic compounds. The interaction can rapidly disrupt their normal metabolism when plasma reactive species contact living cells or organisms, where several chemical reactions may occur when these species encounter organic molecules. Plasma reactive species can be in the form of atoms, molecules, or ions with unpaired electrons.
Free
radicals are very unstable and usually react very fast with other molecules,
which is extremely important in plasma treatment. The plasma technology has
explored several chemical reactions with these non-toxic, free radicals,
opening opportunities to improve product quality. Hence, the air plasma free
radicals include hydroxyl (HO•), superoxide (O2• −), alkoxyl (RO•),
peroxyl (ROO•), and nitric oxide (NO•). The air plasma non-radical species
include ozone (O3), hydrogen peroxide (H2O2),
and singlet oxygen (1O2). The concentration of these species in
plasma depends on the plasma technology being used, the operating conditions
used to generate plasma, and environmental conditions (such as temperature and
relative humidity). Among the reactive oxygen species (ROS), hydroxyl radical
is the most potent oxidant, followed by ozone and alkoxyl radicals, which react
very rapidly with nearby molecules when they are formed.
Applications
Cold
plasma can be successfully used for microbial destruction on fresh products to
increase shelf life as an alternative source for surface sterilization and
disinfection process, which can act on both vegetative cells and spores with
shorter periods. The destruction of microbial DNA by UV irradiation,
volatilization of compounds from the spore, so-called “etching” of the spore
surface by adsorption is because of reactive species like free radicals.
NTP has been applied in the decontamination of raw agricultural products such as apple, lettuce, almond, mangoes, melon, egg surface, and ready-to-serve food systems (cooked meat, cheese).
The plasma technology offers high potential in food packaging as it enhances the adhesion properties, polymerization and helps in good printability.
Low-temperature gas plasma sterilization allows fast and safe sterilization of packaging materials such as plastic bottles, lids, and films without adversely affecting the properties of the material or leaving any residues.
Cold plasma can be utilized for sterilization of heat-sensitive packing materials like polythene ethylene and polycarbonate as the temperature is low.
Early germination of seeds can be achieved by treating the seeds with plasma due to active particles that penetrate through the seed coat and directly influence the cells inside.
References
https://www.ifst.org/sites/default/files/JamesBradleyTechnologyMovingForwardPlasmafortheFood.pdf
http://www.ijarse.com/images/fullpdf/1525085019_JK1800IJARSE.pdf
https://www.advancedsciencenews.com/plasma-technology-2017-lab-food-industry/
https://doi.org/10.3390/pr9122098/Cold Plasma Processing on Fruits and Fruit Juices: A Review on the Effects of Plasma on Nutritional Quality. Processes 2021, 9, 2098.
https://doi.org/10.1007/s11947-016-1699-9, Understanding the Role of Plasma Technology in Food Industry. Food Bioprocess Technol 9, 734–750 (2016).
Despite the competitive advantages of such innovations, the industry faces a global challenge of ensuring food security for a rapidly growing population due to the nature of the foods and the production methods that are prone to microbial and/or pest contaminations. Thus, the current food industry is focused on enhanced microbial food safety and quality without compromising the nutritional, functional, and sensory characteristics of foods, regardless of the difficulties or costs involved. Hence, the food industry relies on a range of intervention strategies, whereas processing steps are employed at points along the food chain to control contaminants to ensure both product safety and/or extend the shelf-life. The methods and technologies applied are to be the focus on most of the described factors while designing applications for novel tech applications.
One such emerging technology is plasma technology, which is a green processing technology that offers many potential applications and operates between most of the above requirements of the industry. Based on recent research and development data indicates that plasma processing has caught the interest of various areas of industry, including cereal, meat, poultry, dairy, fruits, vegetables, packaging, etc. as it helps to modify the food material for the desirable trait and maintains the nutritional and textural properties in addition to microbial decontamination. Thus, plasma technology can be used to improve microbial quality and prevent rapid physical, chemical, and sensory changes, which has shown that the process is effective in offering higher-quality products for consumption by extending the shelf life of foods.
What is Plasma?
Plasma is referred to as the fourth state of matter, which is an ionized gas comprising several excited atomic, molecular, ionic, and radical species, co-existing with electrons, positive and negative ions, free radicals, gas atoms, molecules in the ground, or excited state, and quanta of electromagnetic radiation (UV photons and visible light).
Only non-thermal plasma is applied to food products. Cold plasma can be generated in gases like helium, argonium, oxygen, nitrogen, and a mixture of these gases. Non-thermal plasma can be formed by electrical, microwave, and radiofrequency power sources that generate a high electrical potential difference between two or more electrodes. There is an increased interest in atmospheric pressure cold plasma technologies in food applications because they do not require vacuum systems and enable continuous material processing.
Helium and argonium plasma generate plasma species that do not react with many bioactive compounds and are mainly used for sanitization. The cold plasma on food consisted primarily of applying jet plasma using helium and argonium, which produced reactive species that are mainly inert to the chemical compounds present in food. These inert gases, and inert plasma, induced minimal chemical changes on the main food constituents, where cold plasma does not alter the food quality while being very efficient in sanitizing it. Later application of cold plasma migrated to the use of nitrogen, air, and modified atmosphere. Hence, air plasma is a potent source of reactive oxygen species (ROS) and reactive nitrogen species (RNS), which tend to react when in contact with living cells or with organic compounds. The interaction can rapidly disrupt their normal metabolism when plasma reactive species contact living cells or organisms, where several chemical reactions may occur when these species encounter organic molecules. Plasma reactive species can be in the form of atoms, molecules, or ions with unpaired electrons.
Applications
NTP has been applied in the decontamination of raw agricultural products such as apple, lettuce, almond, mangoes, melon, egg surface, and ready-to-serve food systems (cooked meat, cheese).
The plasma technology offers high potential in food packaging as it enhances the adhesion properties, polymerization and helps in good printability.
Low-temperature gas plasma sterilization allows fast and safe sterilization of packaging materials such as plastic bottles, lids, and films without adversely affecting the properties of the material or leaving any residues.
Cold plasma can be utilized for sterilization of heat-sensitive packing materials like polythene ethylene and polycarbonate as the temperature is low.
Early germination of seeds can be achieved by treating the seeds with plasma due to active particles that penetrate through the seed coat and directly influence the cells inside.
References
http://www.ijarse.com/images/fullpdf/1525085019_JK1800IJARSE.pdf
https://www.advancedsciencenews.com/plasma-technology-2017-lab-food-industry/
https://doi.org/10.3390/pr9122098/Cold Plasma Processing on Fruits and Fruit Juices: A Review on the Effects of Plasma on Nutritional Quality. Processes 2021, 9, 2098.
https://doi.org/10.1007/s11947-016-1699-9, Understanding the Role of Plasma Technology in Food Industry. Food Bioprocess Technol 9, 734–750 (2016).
