Use of cold plasma treatment as non-thermal method of food processing and preservation

1. COLD PLASMA:
Anovelnon-thermaltechnology
in Foodprocessingandpreservation
PRESENTED BY
SUSHANT MANGESH GAWALI
M.Tech Food Biotech
Amity Institute of Biotechnology
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2. CONTENTS
❶ Introduction
❷ Principle
❸ Methods of generation of Cold Plasma
❹ Effects of Cold Plasma Processing on Food material
❺ Advantages
❻ Disadvantages
❼ Recent Advances in the Cold PlasmaTechnique
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3. INTRODUCTION
• Plasma can be explained as the fourth state of matter after solids,
liquids, and gases.
• When a material is subjected to continuous energy, its state changes
from solid to liquid and further to gas. When the gas is subjected to
further energy, the gas gets ionized and forms free electrons and ions
breaking away from their orbitals.
• This resultant state called plasma, has very high temperatures and
often needs vacuum.
• The Sun, Lightening during rain are some examples of natural
plasmas.
• There are two types of plasma: thermal and non-thermal or cold
atmospheric plasma.
• Cold plasma is generated when the gas is partially ionized at
atmospheric pressure or low-level vacuum.
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4. Cont…
• Cold plasma technology was first invented by Sir William Crookes
in the year 1879.
• Cold Atmospheric Plasma (CAP) is generated at 30-60°C under
atmospheric or reduced pressure (vacuum), requires less power,
exhibits electron temperatures much higher than the corresponding gas
(macroscopic temperature), and does not present a local
thermodynamic equilibrium.
• The resultant cold plasma consists of free electrons, ions, UV
radiation, and reactive chemical species like Reactive Oxygen Species
i.e. O3, O2 and Reactive Nitrogen Species i.e. NO, NO2, etc.
• Several different gases can be used to produce CAP such as Helium,
Argon, Nitrogen, Heliox (a mix of helium and oxygen) and air.
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5. PRINCIPLE
• A non-thermal plasma, cold plasma, cold atmospheric plasma or
non-equilibrium plasma is a plasma which is not in thermodynamic
equilibrium, because the electron temperature is much hotter than the
temperature of heavy species (ions and neutrals).
• The principle of plasma technology is based on the partial ionization
of positive and negative ions, free radicals, charged particles in the
form of electrons and photons, and gas-containing molecules.
• Cold plasma is generated at atmospheric pressure by passing a
process gas through an electric field.
• Electron arising from ionization process, accelerated in this field,
trigger impact ionization processes.
• Free electrons colliding with gas atoms transfer their energy, thus
generating highly reactive species that can interact with the food
surface.
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6. Cold Atmospheric Plasma generation
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7. Basic mechanism:
• At first there is the chemical interaction of radicals, reactive species, or
charged particles with cell membranes.
• Then the UV radiation causes damage to cell membranes and internal
cellular components.
• Finally, DNA strands get broken by UV generated during
recombination of the plasma species.
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8. Schematic representation of processes occurring during
in-package cold plasma treatment
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9. METHODS OF GENERATION OF COLD PLASMA
The plasma generation methods most applied for food processing are
categorized into dielectric barrier discharge (DBD), plasma jet (PJ), corona
discharge (CD), microwave (MW), etc.
1. Dielectric barrier discharge (DBD)
DBD plasma is generated by a high voltage applied between two metal
electrodes (a powered electrode and a ground electrode). One or both
electrodes are covered with a dielectric material, such as a polymer, glass,
quartz, or ceramic, separated by a variable gap ranging from 0.1 mm to
several centimeters.
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10. 2. Plasma jet (PJ)
Plasma jet devices are made up of two concentric electrodes.
The outer electrode is grounded and the inner electrode is connected
to external energy source such as radio frequency source and creates
RF (Radiofrequency) energy. Thus interacts with the working gas in
the target chamber causes ionization and exits through nozzle and
gives ‘jet-like’ appearance.
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11. 3. Corona discharges (CD)
CD is identified as a luminous glow localized in space near
sharp points, edges, or thin wires in a highly non-uniform electric
field. The high electric field near the electrode exceeds the gas
breakdown strength, creating a weakly ionized plasma.
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12. 4. Microwave (MW)
In MW plasma generators, electromagnetic waves typically at
2.45 GHz are emitted by a magnetron and used to produce
microwave discharges. The microwave electric field accelerates the
electrons of gas molecules and forms CP as a result, without
electrodes. This system can produce plasma at low and atmospheric
pressure.
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13. EFFECTS OF COLD PLASMA PROCESSING ON FOOD MATERIAL
Due to the non-thermal nature, CP treatments have shown no or minimal
impacts on the physical, chemical, nutritional and sensory attributes of various
food materials.
1. Colour:
• Various researchers reported no significant loss of color after CP treatments
of strawberry, apples, kiwifruit, cherry tomatoes, lettuce and carrots.
• Whereas some researchers reported minor changes after the CP treatments.
• The changes in the colour could be due to the partial degradation of pigments
such as chlorophyll and anthocyanin, as reported in some studies.
2. Texture:
Many of the reported studies suggest the retention of texture of food products
after CP processing.
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14. 3. pH and Acidity:
• There are several reported studies where CP treatment has been shown
to change the pH of food products.
• The pH and acidity changes after plasma treatment were mostly
attributed to the interaction of plasma reactive gases with the moisture
present in the food products.
4. Protein and Enzymes:
• The mechanisms of protein denaturation by CP could be due to the
interaction of plasma reactive species with amino acids and secondary
structure due to loss of α-helix and β-sheet.
• Factors like the type of protein/enzyme, type of plasma, reactive gas,
processing parameters, sample volume and enzyme media play an
important role on the protein denaturation and enzyme inactivation by
CP.
• E.g. Polyphenol oxidase in Fresh-cut apples showed Linear decrease
in activity with treatment time.
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15. 5. Carbohydrates:
• CP treatment of cashew apple juice resulted in the degradation of all
the reducing sugars, such as fructose and glucose and non-reducing
sucrose.
• A similar decrease in the fructose, increase in the sucrose and
degradation of oligosaccharides with a high degree of polymerization
was also reported after CP treatment of prebiotic orange juice.
6. Vitamins:
• Most of the studies on CP treatment of whole fruits and vegetables
have reported no significant reduction in ascorbic acid content after
plasma treatment.
• However, up to 4% reduction in ascorbic acid content was observed
after plasma treatment of cut fruits and vegetables.
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16. Effects on cereals:
• It was observed that germination and seedling growth in wheat seed
were significantly improved by 20%–30% after plasma jet-DBD
treatment for a short time, compared to untreated samples.
• The plant grown from plasma-treated seed showed increased growth
activity, high dry matter, and improved chlorophyll contents in the
leaves.
Effects on fresh produces:
• CAP treatment reduces the intensity of postharvest respiration rate
which is proven in strawberries, carrots and mandarin.
• CAP application on the cut-fruit increased the freshness and quality.
• CAP application on fresh cut apples is reported to decrease O2
fixation and increase CO2 focus in the gaseous environment, causing
changes in the cell respiratory pathway which triggers the inactivation
of endogenous enzymes of fresh fruits and vegetables, which delays
the browning and maturing process.
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17. Effects on milk and milk products:
• CAP treatment on milk influences the physicochemical and textural
properties, but these changes depend on the flow rate and time.
• The quality of milk and milk products have been im-proved after
plasma treatment with effective inhibition of pathogens.
• In contrast, CAP has a significant drawback in treating plant-based
milk, which negatively influences its protein proportion.
Effects on meat products:
• CAP treatment positively influences the quality of meat products as
reported by many researchers.
• Some studies also demonstrated that using any combination of gas in
CAP would decrease spoilage causing bacteria on meat.
• Further modification in the gas mixture also influences the water
activity in meat products.
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18. ADVANTAGES
• Microbial inactivation efficiency can be achieved at low temperature.
• Suitable for treating sensitive raw and fresh food products.
• Requires less power input for operation.
• Low impact on the internal product matrix.
• Doesn’t alter or damage the key food nutrients.
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19. • Reduces the risk caused by thermal and chemicals processing of
food materials.
• Reduces water usage and solvent system for processing.
• CAP do not alter the sensory and nutritional properties of food
materials.
• Plasma is environmentally safe once the reactive species are
withdrawn from the power supply.
• Equipment cost is low when least cost noble gases are used for
processing.
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20. DISADVANTAGES
• Treatment of bulky and irregularly shaped food is difficult.
• Restricted volume and size of the food for treatment because
microbial inactivation occurs on the food surface and thus reactive
plasma species can only penetrate foods to a limited extent.
• The rough surface of some products provides numerous sites for
microorganisms to attach and potentially escape antimicrobial
treatment.
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21. • Several ROS has limited penetration into food products.
• It may affects the sensory and nutritional attributes of the food to
some extent during processing.
• It may accelerate lipid oxidation and causes negative impact.
• It can change the colour and firmness of fruits.
• High cost operation in case of use of Helium, etc.
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22. RECENT ADVANCES IN THE COLD PLASMA TECHNIQUE
• A new research trend suggests that CP technology is a powerful and
profitable technology for the food industry.
• The non-thermal technology like cold plasma, is highly advantageous
for microbial decontamination of food products including sporulating
and spoilage/pathogenic organisms.
• The utilization of CP technology in food processing includes
functionality modification of food components, enhancement of seed
germination performance, improved physiochemical properties of
grains and degradation of agrochemical residues.
• CP application has recently been expanded into hydrogenation of
vegetable oils to yield trans-free edible oils, inactivation of anti-
nutritional factors, control of food allergens, etc.
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23. • Plasma is also a promising technology for the control of pests in
stored cereal crops.
• Plasma processes can be used to modify the surface properties of
cereal grains. Plasma treatment can also induce changes in the
crystallinity and gelatinization of starch.
• Cold plasma oxidation has emerged as a promising technology for
aqueous and gaseous pollutant removal.
• Cold plasma has evolved as a unique pretreatment tool for anaerobic
digestion of food waste.
• Atmospheric plasma pretreatment of wheat straw followed by
fermentation improved the ethanol yield by up to 52%.
• Plasma treatment of seeds can be effective in preventing fungal
growth and further mycotoxin production.
• Cold plasma have also been employed for the processing of
packaging materials in order to improve barrier properties and confer
antimicrobial activity.
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24. REFERENCES
• Yilmaz Ucar, Zafer Ceylan, Mustafa Durmus, Oktay Tomar, Turgay
Cetinkaya (2021). Application of cold plasma technology in the food industry
and its combination with other emerging technologies. Trends in Food Science
& Technology, 114: 355-371.
• R Baghya Nisha and Rita Narayanan (2019). Review on cold plasma
technology: The future of food preservation. International Journal of Chemical
Studies, 7(3): 4427-4433.
• N. N. Misraa, Ximena Yepezb, Lei Xub, Kevin Keenera (2019). In-package
cold plasma technologies. Journal of Food Engineering, 244: 21–31.
• Shashi K. Pankaj, Zifan Wan and Kevin M. Keener (2018). Effects of
Cold Plasma on Food Quality: A Review.
• Chaitanya Sarangapani, Apurva Patange, Paula Bourke, Kevin Keener
and P. J. Cullen (2018). Recent Advances in the Application of Cold Plasma
Technology in Foods. Annual Review of Food Science and Technology.
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25. THANK
YOU...