Plasma processing uses ionized gases known as plasma to kill microorganisms and modify surfaces. The document discusses the principles and techniques of plasma generation including corona discharge, dielectric barrier discharge, and plasma jets. Factors that affect plasma treatment and its effects on microorganisms, enzymes, food quality parameters like color and nutrients are described. Applications of plasma in food processing, packaging, and seed treatment are also covered. Plasma processing provides an effective non-thermal method for food preservation and surface modification with advantages of high efficacy, ambient operation, and minimal effects on food quality.

1. PLASMA PROCESSING
BY,
K.VINITHA
2018694619

2. INTRODUCTION:
■ Electrodynamics: Phenomena of moving electrical charges and their interaction with
electric field.
■ Electro spinning: Produces Nano fibres from polymeric solution.
■ Electro spraying: similar to electro spinning produces Nano beads instead fibres.
■ Plasma: Produces excited atoms, molecules, radical species, ions when gas is ionized.
process Operating voltage (KV) Distance between the
electrodes.(cm)
Electro spinning 15-25 30
Electro spraying 30 30
PEF ≤100 1.7
Cold plasma (DBD) 5-20 0.02-0.5

3. ■ Plasma is referred as the fourth state of matter.
■ It comprises excited atomic, molecular, ionic and radical species,
coexists with numerous reactive species.
■ Classified based on ionisation
■ Sub-divided into equilibrium (high temperature) and non-equilibrium
(low temperature) plasma.
■ Low temperature plasma is further divided into quasi-equilibrium
plasma (100-150 °c ) and cold plasma / non-thermal plasma (<60 °c).
Plasma
Free
radicals
photons
Negative
ions
Positive
ions
Atoms
Molecule

4. HISTORY:
■ Sir William Crookes in 1879 discovered the fourth state of matter
while conducting experiment with electrical discharge tube.
■ In 1928, American scientist Irving Langmuir proposed electrons,
ions and neutrals in an ionized gas entrained in fluid medium and he
termed it as “Plasma”.
■ The first time sterilization property of plasma was introduced in the
end of 1960’s and patent was assigned to Menashi,1968.

5. PRINCIPLE:
■ Cold plasma can be obtained at atmospheric or reduced pressures.
■ When a gas gets in contact with an electric field , which increases the kinetic
energy of the electrons resulting in increased number of collisions with the gas
atoms to ionize and excite them.
■ Plasma products like electrons, positive ions, radicals, excited atoms and
photons including that in the UV ranges.
■ Resulting highly reactive chemical species (1O2, HO• , O−
2 , H2O2, O3) are capable
of inactivating a wide range of micro organisms including pathogens and
spoilage organisms.

7. ■ There are two processes that occur during the creation of plasmas which
give them their unique properties:
(1) ionization – Dominates during plasma development (e.g., electrical
breakdown of gas molecules).
when a high-energy electron “knocks out” an electron from electronically
excited atoms or molecules;
A + e− → A+ + 2e−
(2) recombination -dominates during plasma decay, when the ionization
energy of plasma converts to heat, chemical energy, light, etc.
AB+ + e− → (AB)∗ → A + B∗
net effect is to fracture the original molecule AB into smaller reactive
chemical species.

9. PLASMA GENERATION TECHNIQUES:
■ Plasma can be produced by subjecting a gas to an electric
field , either of direct current field or high frequency field
■ Plasma generation techniques includes
• Corona discharge,
• Dielectric barrier discharges (DBD),
• Radio frequency plasma (RFP) and
• Glow discharge plasma
■ With regards to food processing, dielectric barrier discharge
and jet plasma are most commonly used.

10. CORONA DISCHARGE:
■ Coronas are non-uniform discharges develop in the high field
region near the sharp electrode spreads out to the planar
electrode.
■ It is the characteristic of an asymmetric electrode pair and
results from the electric field powered with a continuous /
pulsed dc voltage.
■ (1-100µA at high voltage of several orders of kV)
■ In a highly non-uniform electric field, the high electric field
near the point electrode far exceeds the breakdown strength
of the gas and an ionized plasma is created.
■ Colour releases due to recombination of ions and electrons
Adv: High efficiency, low
investment & operational cost
Uses: Surface treatment for
tissue culture, surface treatment
of materials to change
properties, sanitization of water,
generation of ozone.

11. DIELECTRIC BARRIER DISCHARGE
(DBD):
■ DBD consists of two flat metal electrodes covered with
dielectric material and kept at 0.1mm to 5mm gap.
■ AC/DC can be used. AC preferred.
■ The typical frequencies high voltage supplies are 0.05 – 500
kHz. The voltage amplitudes of the order of 5 – 20 kV
produce electric currents in the range of 10 – 100 mA.
■ Dielectric barriers act as a stabilizing material, avoids any arc
transition, and help in creating a large number of micro-
discharges for homogeneous treatments.
■ DB can be Glass, Ceramic, Quarts & polymers .
Advantages:
• Simple, reliable.
• Easy scalability into a continuous
system.
• Enhanced antimicrobial efficacy
• Prevents of cross contamination.
Uses:
• Food decontamination
• Surface treatment
• Ozone generation

12.  The floating-electrode DBD (FE-DBD) consists of an insulated high voltage
electrode and an active electrode (not grounded).
 The powered electrode needed to be (< 3mm) close to the surface of the
second electrode to create the discharge.
RADIO FREQUENCY PLASMA JETS:
 Atmospheric Pressure Plasma Jet (APPJ) consists of two coaxial electrodes
between which a feed gas flows at a high rate.
 The inner electrode is connected to a radio frequency power (50-100W) at
13.56 MHz high frequency causes ionization of the working gas.
 Produces a high velocity effluent stream of highly reactive chemical species.
 Central electrodes driven by radio frequency power accelerate free
electrons that collides with feed gas and generates plasma.

14. PLASMA NEEDLE:
 The plasma needle consists of a 0.3 mm metal strand diameter
with a sharpened tip.
 The gas is then mixed with air at the needle tip where a micro
discharge is created.
 Micro plasma is created when RF power at 13.05 MHz ranging
between 10 mW and several watts is applied to the needle.
.
ADVANTAGES:
 It operates without a dielectric cover over the electrode
streamers and arcing are created.
 The gas temperature of the discharge is as low as 50°C,
allowing it to treat delicate surfaces without damage,

15. GLOW DISCHARGE PLASMA:
■ Electrical field across the cathode and anode plate causes the
acceleration of electrons in the front end of the cathode which
leads to ionization and excitation.
■ Held at low pressure (about 1/10000th to 1/100th of
atmospheric pressure).
■ The increase ionization collisions increase the concentration of
new electrons and ions at the cathode build the discharge glow
of self-sustaining plasma.

16. Free radicals measurement:
■ Electron paramagnetic resonance (EPR) spectroscopy - this is also referred to as
electron spin resonance (ESR) spectroscopy,
■ Spin trapping
■ Reaction fingerprinting
• EPR detects radicals directly but is limited to relatively
stable radicals.
• EPR detects the rate of absorbance between the two
spin energy levels associated with an unpaired electron
• The absorbance is induced when the substance with
the unpaired electron is placed in a magnetic field.
• Non-radicals, that is substances with paired electrons,
are not detected by EPR, because the magnetic effects
on the electron spin cancel each other out

17. Factors affecting plasma treatment:
Processing parameters:
Choice of Gas: Determine effectiveness of sterilization
Type of active species generated.
Types of free radicals formed are a direct result of the ionized constituent gas molecules.
Common gas : O2,N2, O2/N2, O2/Ar, He, and air.
Gas Flow Rate: Increasing the gas flow rate, increases the flux of active species on the medium,
which increases the effectiveness of the treatment.
Power: Increase in electron density, which allows for a larger volume of active species to interact
with the medium
 Distance between electrode and sample.
 Treatment time
Product parameters: size, geometry, surface shape.

18. EFFECT ON MICROORGANISMS:
■ Chemical interaction of cell membranes with reactive molecules (¹O2, O3,
NO, etc.) or charged particles (electrons, and atomic or molecular ions);
■ ROS - destabilization of membranes, DNA damage and oxidation of low-
density lipoprotein.
■ Radical bombardment on the surface of the cell with great intensity.
■ Oxidation of the lipids, amino acids and nucleic acids.
■ Acts on the doubled bond of unsaturated fatty acids of membrane cell.

20. • Proteins of the cells and the spores vulnerable to the action of the species, causing denaturation
and cell leakage.
• UV photons of different wavelengths involve in dimerizing of the thymine bases of DNA including
that of spores.
• Combination of multiple mechanisms will have the greatest sanitizing efficacy.
• The joint action of radicals and UV photons also facilitates bacterial inactivation.

21. EFFECT ON ENZYMES:
■ The changes in the structure of protein are largely due to the chemical reactions between
the protein polymer and the active chemical species of cold plasma.
■ The loss of secondary structures, viz. helical and ordered β-sheet elements on exposure to
cold plasma was shown for PPO, POD and alkaline phosphatase.
■ O atoms abstracts hydrogen from the protein polymer backbone and creates radical sites
that lead to the cleavage of the polymer chain.
■ Hydroxyl radicals (OH•), superoxide anion radicals (O2¯•), hydroperoxyl radical and nitric
oxide (NO• ) modifies the reactive side-chain of the amino acids, such as cysteine, aromatic
rings of phenylalanine, tyrosine, and tryptophan causes loss of enzyme activity.
■ Eg: Polyphenol oxidase in cold plasma treated guava pulp and whole fruit was reduced
by 70 % and 10%in 300 s at 2 kv respectively.

23. EFFECT ON FOOD QUALITY:
COLOUR
• The product type, plasma treatment parameters and storage
conditions are the critical factors affecting the color.
• No significant loss of color after CP treatments of strawberry,
apples, kiwifruit, cherry tomatoes, lettuce and carrots.
• Redness improvement in pork jerky
• Degradation of pigments show color loss
TEXTURE
• Retention of texture of food products after CP processing.
• Decrease in firmness was reported after CP treatment of blueberries.
• The softening of the blueberries due to the high air-flow rates of the
plasma jet during the treatment.
• Increase in viscous and elastic behavior of strong wheat flour
PH AND ACIDITY
• CP shows change in pH and acidity of food products
• Mostly attributed by interaction of plasma reactive gases with the
moisture present in the food products.
• In solid food, plasma species reacts with the surface water, forming acidic
compounds only on the surface.
• Nitric acid induced by RNS (NO) acts as the reason for acidification in air
plasma treatments.

24. PROTEIN:
Protein denaturation by CP occurs due to the
interaction of plasma reactive species with
amino acids and secondary structure due to
loss of α-helix and β-sheet .
CARBOHYDRATE:
• CP treatment of cashew apple juice resulted
in the degradation of all the reducing sugars,
such as fructose and glucose.
• Changes in crystalline structure of starch
granules.
• Increases in degree of gelatinization.
• Decreases cooking time of brown rice.
LIPIDS
• An increase in lipid oxidation in fresh pork and
beef after treating it 10 min.
• An increase in lipid oxidation of pork loin was
observed with oxygen-containing plasma gas.
• significant lipid oxidation in fresh mackerel
fillets. (observed an increase in PV from 6.89 to
37.57 meq. active oxygen/kg lipids).

25. ANTIOXIDANT ACTIVITY:
• Degradation flavonoids can be observed
• No significant effect in apples, blueberries
and kiwi
• Type of food products, plasma generation
source, mode of exposure and treatment
parameters are critical in controlling
VITAMIN:
• Some vitamins, such as B2,B6,biotin-usually stable
others A, C and E, are relatively labile
• Whole fruits and vegetables - no significant reduction
in ascorbic acid content
• up to 4% reduction of cut fruits and vegetables.
• Degradation is attributed by the reaction with ozone
and other oxidizing plasma.
• Sample type (whole/cut), processing time and plasma
gas are the critical factors

26. EFFECT ON SEED GERMINATION:
■ Penetrates active particles through the seed coat and directly influencing cells inside.
■ The increase in germination rate is due to changes on the surface caused by plasma
treatment.
■ The interaction of cells with plasma might result in DNA damage, cell wall fracture, can
stimulate natural signal like production of growth factors, changing the protein structure,
affecting enzymatic activity leading to breakdown of seed dormant stage.
■ Increase in germination of legumes by 10–20 % and also lowered the fungicidal effect by 3–
15 % were observed.
■ Surface etching by high ion energy particles increase in germination rate of seeds by 50 %
after the treatment.

27. IN PACKAGING
 Easy printability , anti-mist properties → surface activation and functionalization
by plasma .
• Significantly improves adhesiveness and wettability.
 Gas permeation barrier ,chemical safety → plasma deposition of barrier coatings
• CF (carbon fluoride free radicals) -layers deposited on PE as barrier against organic
solvents
• significant reduction of gas (oxygen, carbon dioxide) and water vapour
permeability.
• Good adhesion of those barrier coatings to the surface of the polymer packaging
material maintains transparency and flexibility
 Microbiological safety → plasma sterilization

28. PLASMA ACTIVATED WATER:
■ The type and the concentration of the reactive species
that are present in PAW depend on the gases used to
generate plasma.
■ For example, the use of oxygen, nitrogen and water as
parent molecules for the production of PAW, result in
primary species (including atomic oxygen, singlet oxygen,
superoxide, ozone, hydroxyl radicals and and atomic
nitrogen) which continue to react to form secondary
species including hydrogen peroxide, peroxynitrite, nitric
oxide, nitrates and nitrite ions)

29. Generation technique:
contact of the plasma streaming with the water while the other
induces the plasma directly into the water.
 Changes in PH, redox potential , conductivity were observed.
 The chemical species formed in the plasma and water results in the
acidification reaction results in the generation of nitric acid, and
peroxynitrous acid.
 The low pH have proven synergistic antimicrobial effects against
bacteria, yeasts and other microorganisms.

30. For example: Nonthermal atmospheric pressure plasma jet, Ar/O2-based plasma was
generated at 18 kV over sterile deionized water for either 10 or 20 min.
Plasma-generated chemically reactive species tend to penetrate the water phase and
change the chemical composition of water, thereby inducing bactericidal activity.
Inoculated fruits were immersed in 10 or 20 min-PAW for 5, 10, or 15 min and stored for
either 0 or 4 days at 20°C.
PAW achieved substantial reduction of S. aureus inoculated on strawberries ranging from 1.6
to 2.3 log. Bacterial numbers tended to decrease further by a log after 4 days of storage.

31. APPLICATIONS:
■ Sterilize seeds while in storage.
■ Enhance seed germination
■ Treatment, sterilization, and cleaning of water used for
produce washing after harvest
■ Disinfection of produce before packaging
■ Control of pests and pathogens at the in-store display
case and in-store storage

32. • High efficiency at low temperatures,
• Precise generation of plasmas suitable for the intended use. (ultrafast preservation/
sterilization process)
• low impact on the internal product matrix;
• free of water or solvents; no residues;
• relatively low energy consumption ,low running cost and generally moderate cost.
• Operates at ambient temperature (ideal for thermolabile products).
• Environmental friendly.
(Operational cost: Based on power consumption of the NTP, the nature and flow rate of the gas
used, wear and tear on electrodes. Systems which use air as the feed gas will be less expensive
than those which use a pure gas (Ar, He, etc.), or a defined gas mixture).
ADVANTAGES:

33. LIMITATIONS:
■ Products with high lipid content cannot be processed.
■ It is less possible to inactivate of endogenous enzymes.
■ Operating with noble gas turn to be expensive.
■ Controlling of gas plasma reactions with food substrate.
■ Depending on the gas mixture, the one atmosphere uniform glow
discharge plasma system can generate a high amount of ozone.

34. • Emerging non-thermal technology.
• Microbial destruction and surface modification of
substrate
• High efficacy, preservation and does not introduce toxicity
to the medium.
• Effective at ambient temperatures
• No or minimum effects on nutritional and sensory quality
parameters of food with no chemical residues
SUMMARY:

35. REFERENCE:
■ Bermudez-Aguirre D, Wemlinger E, Pedrow P, Barbosa-Canovas, Garcia-Perez M, Effect of atmospheric
pressure cold plasma (APCP) on the activation of Escherichia coli in fresh produce. Food Control, 34, 2013,
149-157
■ Brisset, J. L., & Pawlat, J. (2016). Chemical effects of air plasma species on aqueous solutes in direct and
delayed exposure modes: discharge, post-discharge and plasma activated water Plasma Chemistry and
Plasma Processing 36(2) 355-381.
■ Laroussi M., Mendis D.A. & Rosenberg M. (2003). Plasma interaction with microbes. New Journal of Physics
Vol. 5, 41.1–41.10.
■ Misra, N.N.; Pankaj, S.K.; Segat, A.; Ishikawa, K. Cold plasma interactions with enzymes in foods and model
systems. Trends Food Sci. Technol. 2016, 55, 39–47.
■ Pankaj, S. K., Wan, Z., & Keener, K. M. (2018). Effects of Cold Plasma on Food Quality: A Review. Foods, 7(1), 4
■ Rohit Thirumdas , Chaitanya Sarangapani ,Uday S. Annapure. (2014). Cold Plasma: A novel Non-Thermal
Technology for Food Processing.Review,Food biophysics.