Cold Plasma processing
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Cold plasma processing uses ionized gases produced by non-thermal techniques to sterilize and extend the shelf life of foods. Plasma is ionized gas consisting of electrons, ions, and molecules that can be produced through techniques like corona discharge or dielectric barrier discharge. Cold plasma is effective at reducing microbes like bacteria and fungi on foods while minimally impacting quality. It has shown potential for use in industries like cereal, meat, fruit/vegetables, spices, dairy, and food packaging. Research institutes are further exploring cold plasma processing for food safety and quality.
Cold Plasma processing
- 2. What Is Cold Plasma - Application on ionized gas produced by non- thermal techniques on food to impart its sterilizing and shelf life enhancing properties.
- 3. What is Plasma ? • Plasma is an ionized gas consisting of free electrons, ions, reactive atoms, neutral molecules and photons • A plasma is a very good conductor of electricity and is affected by magnetic fields. • Plasmas, like gases have an indefinite shape and an indefinite volume.
- 4. Classification of plasma • Thermal • Non-thermal(cold) Temperature • Low pressure • Atmospheric pressure • High pressure Pressure • Microwave • Radio frequency • Corona • Dielectric barrier Discharge Mode • Air • Oxygen • Helium • Argon Gas
- 5. Some facts about plasma sterilization of foods
- 6. Some facts about plasma sterilization • In 1960’s for the first time sterilization property of plasma was introduced, and a patent was filed in the year 1968 • Destruction of 10^6 spores in inner surface of vials occurred in less than second using argon plasma by pulsed RF field atmospheric plasma. • Boucher, and Bithell reported that electrical discharge in particular gases can lead to complete sterilization • Plasma can penetrate upto 10 micrometer, 10 times deeper than UV rays, which is helpful for the destruction of sporulated bacteria
- 7. • Nelson and Berger reported that O2 plasma showed efficient biocidal action on B. subtilis and Clostridium sporogenes as these two were considered as the most resistant bacteria • Plasmas generated at 200 W were sufficient to reduce the population of B. subtilis more than 3.5 log10 in 5 min. From then the utilization of plasma for sterilization was commercialized
- 8. How cold plasmas are produced?
- 9. Corona Discharge • characteristic of an asymmetric electrode pair and results from the electric field. • Gas is passed through point discharge where electric field is very strong resulting into formation of ions. • This spreads out towards planar electrode.
- 10. Radio Frequency(RF) • It consists of two concentric electrodes through which a mixture of helium, oxygen or other gases flows • Inner electrode is coupled to 13.56 MHz radio frequency power at a voltage between 100-250 V • These energetic electrons undergo inelastic collisions with the feed gas, producing excited state molecules, atoms, free radicals and additional ion electron pairs
- 11. Dielectric barrier discharge • DBD is the electrical discharge between two electrodes separated by an insulating dielectric barrier. • Originally called silent (inaudible) discharge and also known as ozone production discharge. • It was first reported by Ernst Werner von Siemens in 1857. • operate at approximately atmospheric pressure (typically 0.1–1 atm). An A.C. voltage with amplitude of 1–100 kV and a frequency of a few Hz to MHz is applied to the discharge
- 12. Construction of DBD • Two electrodes • Dielectric barrier near electrodes • A gas flow • Ac power supply
- 15. Advantages of Cold Plasma • The most attractive features of plasma are their low temperature property, and high efficiency • Increases shelf life without affecting sensory qualities • Very less nutrient loss as compared to other heat treatments • No chemical treatment required • Very less time required for treatment
- 16. Applications of cold plasma Proceessing
- 17. 1. Cereal Industry • This technology offers various benefits in cereal industry in addition to the decontamination. • 1. Plasma processing is used to modify the properties of brown rice:- Sarangapani et al. (2015) studied the effect on cooking and textural properties of parboiled rice under various treatment time and power. - It increased the water uptake ratio of parboiled rice and also reduced the cooking time up to 8 min. - Textural properties were improved after treatment as hardness and stickiness decreased with increase in power and time.
- 18. Chen et al. (2012) used the low-pressure plasma to modify the microstructure, cooking, and textural properties of brown rice - Treatment results in an etching of brown rice surface, which allows water to be easily absorbed by the rice kernel during soaking - cooking time of brown rice is reduced, and the cooked brown rice has a soft texture and is easier to chew
- 20. 2. N.N. Misra et al.(2014) studied ACP treatment of wheat flour(Hard & soft) • Samples of 250gm were placed in commercial 270 mm thick polyethylene terephthalate trays, sealed with a high barrier 50 mm films. • The atmospheric air condition at the time of treatment was 45 ± 1% relative humidity (RH) and 20 ± 2 ˚C. • Discrete voltages of 60 and 70 kV were applied across the electrodes for 5 and 10 min • The rheological properties of flours revealed an improvement in the dough strength and optimum mixing time for both strong and weak wheat flours • The elastic and viscous moduli of strong wheat flour progressively increased with applied voltage and treatment time
- 21. • Average values of elastic modulus (G’) and viscous modulus (G’’) for the dough from untreated and ACP treated flours are shown in Table • The G’ of the dough from all the flours was greater than G’’, indicating a predominance of anelastic soft solid nature for the dough
- 22. 3) The Effect of Plasma on Fungus Colonization of Wheat Grain and Seed Quality • Leszek Kordas et al. (2014) :- -Conducted The assessment of both the effectiveness of spore destruction and of seed quality under 3-, 10-, and 30-second exposures. - The voltage was set at 8 kV. - 200 seeds were selected from each variant of the experiment
- 23. - Exposure of winter wheat grain to low temperature plasma resulted in the reduction of the number of colonies of fungi forming on grain in the optimum time of 10 seconds. - The results also showed a positive effect of the use of cold plasma on the basic values determining seed lot quality.
- 25. 2. Meat and Poultry Industry • The various food safety intervention technologies-slaughtering, meat product fabrication (e.g., cutting, blending, and extruding), processing (e.g., cooking, curing, drying, and freezing), packaging and also utilize intervention technologies to ensure a sanitary manufacturing environment. • Plasma processing offers a wide selection of gas compositions, generation methods, and methods of product exposure
- 26. 1) Atmospheric pressure plasma treatment on ready-to-eat by (Rod et al. 2012). • The inoculated meat samples in bags containing 30 % oxygen and 70 % argon were placed between electrodes’ • Treated at 15.5, 31 and 62 W for 2 to 60 s. • Highest inactivation rates = 1.5 to 1.6 log cfu/gm for 20 s treatment time interval of 10 min at operating powers of 15.5 and 62 W. • Surface color changes included loss of redness of 40 and 70 % after 1 and 14 days of storage, respectively, regardless of plasma treatment
- 27. 3. Fruit and Vegetable Industry • Promising technology used in fruit and vegetable processing industry since last decade to improve the quality of produce • Capable of reducing microbial populations on produce surfaces.
- 28. 1) In-package atmospheric pressure cold plasma treatment of strawberries N.N. Misra et al.(2013)
- 29. • Strawberries were treated (ACP),generated with a 60 kV power pulsed at 50 Hz, across a 40 mm electrode gap, generated inside a sealed package containing ambient air (42% relative humidity) • Aerobic mesophillic bacteria, yeast and mould were reduced by 2 log10 within 24 hours pf post-ACP of 5 min • The respiration rate of produce after treatment showed no significant difference • Also, colour and firmness changes were insignificant.
- 31. 2) Tomato peroxidase inactivation by atmospheric pressure cold plasma based on DBD S.K. Pankaj et al.( 2013) • The kinetics of inactivation of tomato peroxidase as a model enzyme was studied at 30, 40 and 50 kV, for up to 5˚ of atmospheric air dielectric barrier discharge plasma treatments
- 32. • Treatment conditions were found to influence the inactivation rates and the shape of the inactivation curve. • The results from this study indicate that cold plasma can inactivate enzymes, in addition to the reported studies on microbial inactivation.
- 33. 3) Effect of atmospheric pressure cold plasma (APCP) on the inactivation of Escherichia coli in fresh produce Daniela Bermúdez et al.(2013) • Experiment was carried out on three produces namely lettuce, baby carrot and tomatoes • Tested voltages were from 3.95 kV up to 12.83 kV at 60 Hz with processing times from 30 s up to 10 min and The argon flow rate was 455.33 sccm. • Samples were placed on sterile petri dishes in the plasma treatment chamber on top of the stage (about 2 cm from the mesh)
- 34. - 1.6 log cfu/g. was the average rate of inactication at highest power and for longest time -Tomatoes, followed by lettuce, were easier to disinfect than carrots, maybe because of the surface structure. -Color parameters did not show significant changes after processing. However, the structure of E. coli cells showed a totally damaged surface
- 35. 4. Spice Industry • Plasma processing also used for decontamination of spices and showing the promising results. • However, indirect application of ACP is preferred over direct ACP
- 36. 5. Dairy Industry • Current thermal decontamination methods are known to induce changes to the chemical and physiological composition of milk and milk products. • Due to its complex structure, milk has so far shown to be highly sensitive to many current novel technologies • Using the advantages of cold plasma, this system was tested for its ability to decontaminate milk and milk products
- 37. 1) Low temperature plasma for decontamination of E. coli in milk. Guro et al.(2012) • Infectious diseases caused by the ingestion of pathogenic bacteria in contaminated milk are still a major health concern • The time dependent effect of atmospheric corona discharge generated with 9 kV of AC power supply on E. coli ATCC 25922 dispersed in whole, semi skimmed and skimmed milk was examined. • Plasma was applied at time intervals of 0, 3, 6, 9,12, 15 and 20 min • A significant 54% reduction in the population of E. coli cells after only 3 min was observed regardless of the fat content of the milk.
- 38. • The initial pre-plasma bacterial count = 7.78 Log CFU/ml • The final pre-plasma bacterial count = 3.63 Log CFU/ml • No viable cells were detected after one week examination in whole milk samples and remained so over the 6 week storage period.
- 39. 5. Packaging Industry • Food packaging materials are aimed at serving the functions of both preserving food and protecting it from deterioration and outside contamination. • When not stored in proper conditions, packaging materials can get contaminated with microorganisms. • Plasma-treated material provides tremendous advantages to a package.
- 40. 1) remove all unwanted organic contaminants 2) Surface treating, or activating a material to gain an increased wettability quality, 3) The deposition of substrates onto a material, adding desired new qualities.
- 41. • It was originally developed to increase the surface energy of polymers, enhancing adhesion and printability. • New trends aim to develop in package decontamination, offering non-thermal treatment of foods post packaging. • Surface treatments of packaging can serve various purposes including surface functionalisation, surface cleaning or etching, and surface deposition.
- 42. • The properties which can be controlled by using ACP on packaging materials are:- Contact angle - Roughness - Crystallinity - Wettability
- 43. INSTITUTES AND INDUSTRIES PROMOTING COLD PLASMA PROCESSING 1) Wageningen University and Research Centre ,University in Wageningen, Netherlands Focused work on:- a) Disinfection of packaging materials b) Disinfection of food products 2) Campden BRI, U.K. in collaboration with the University of Liverpool
- 44. Comparison among PEF, ACP AND HPP ACP • Electric impulses can be applied homogeneously through the product with strong intensities • Preservation of liquid media • Permeabilisation of plant and animal tissue • Shelf life improvement • Microbial safety PEF • Uses cold gases to disinfect the surfaces of packaging or food products(by making ions of gases). • Disinfection of packaging materials • Disinfection of food products • Shelf life enhancement HPP • Under these high pressures(up to 1000 MPa) macromolecules are altered • High pressure pasteurisation • High pressure sterilisation • High pressure product modification • Very high pressure kills only pathogens
- 45. References • Niemira, B.A., 2012. Cold plasma decontamination of foods. Annual Review of Food Science and Technology 3 (1), 125–142. • Scholtz, V., Pazlarová, J., Soušková, H., Khun, J., & Julák, J. (2015). Nonthermal plasma—a tool for decontamination and disinfection. Biotechnology Advances, 33, 1108–1119. • Poutanen, K., Sozer, N., & Della Valle, G. (2014). How can technology help to deliver more of grain in cereal foods for a healthy diet Journal of Cereal Science, 59, 327–336 • Hertwig, C., Reineke, K., Ehlbeck, J., Erdoğdu, B., Rauh, C., & Schlüter, O. (2015a). Impact of remote plasma treatment on natural microbial load and quality parameters of selected herbs and spices. Journal of Food Engineering, 167, 12–17. • Bermudez-Aguirre, D., Wemlinger, E., Pedrow, P., Barbosa-Canovas, G., & Garcia-Perez, M. (2013). Effect of atmospheric pressure cold plasma (APCP) on the inactivation of Escherichia coli in fresh produce. Food Control, 34, 149–157.
- 46. • Misra, N.N., Kadam, S.U., Pankaj, S.K., 2011a. An overview of nonthermal technologies in food processing. Indian Food Industry 30 (5–6), 45–52. • Perni, S., Shama, G., Kong, M.G., 2008. Cold atmospheric plasma disinfection of cut fruit surfaces contaminated with migrating microorganisms. Journal of Food Protection 71 (8), 1619–1625 • Critzer, F., Kelly-Wintenberg, K., South, S., Golden, D., 2007. Atmospheric plasma inactivation of foodborne pathogens on fresh produce surfaces. Journal of Food Protection 70 (10), 2290 • Wang, R. X., Nian, W. F., Wu, H. Y., Feng, H. Q., Zhang, K., Zhang, J., et al. (2013). Atmospheric-pressure cold plasma treatment of contaminated fresh fruit and vegetable slices: inactivation and physiochemical properties evaluation. The European Physical Journal D-Atomic, Molecular, Optical and Plasma Physics, 66, 1e7. • Gurol, C., Ekinci, F. Y., Aslan, N., & Korachi, M. (2012). Low temperature plasma for decontamination of E. coli in milk. International Journal of Food Microbiology, 157, 1–5.
- 47. • Segat, A., Misra, N. N., Cullen, P. J., & Innocente, N. (2015). Atmospheric pressure cold plasma (ACP) treatment of whey protein isolate model solution. Innovative Food Science and Emerging Technologies, 29, 247–254. • Todd, E. C. D., & Notermans, S. (2011). Surveillance of listeriosis and its causative pathogen, Listeria monocytogenes. Food Control, 22, 1484–1490. • Tiozzo, B., Mari, S., Magaudda, P., Arzenton, V., Capozza, D., Neresini, F., & Ravarotto, L. (2011). Development and evaluation of a riskcommunication campaign on salmonellosis. Food Control, 22, 109– 117 • CZAPKA T., KACPRZYK R., KORDAS L., PUSZ W. The influence of the non thermal plasma on the biological properties of the seed-grain. Electrical Review, 11/b, 222, 2012B • ie, P., Pu, H., Zhang, B., Su, J., Chen, L., & Li, X. (2015). Structural characteristics and rheological properties of plasma-treated starch. Innovative Food Science and Emerging Technologies. doi:10.1016/ j.ifset.2015.11.019. • Chen, H.H., Chen, Y., & Chang, C.H. (2012). Evaluation of physicochemical properties of plasma treated brown rice. Food Chemistry, 135, 74–79
- 48. • Korachi, M., Ozen, F., Aslan, N., Vannini, L., Guerzoni, M. E., Gottardi, D., & Ekinci, F. Y. (2015). Biochemical changes to milk following treatment by anovel, cold atmospheric plasma system. International Dairy Journal, 42, 64–69. • Thirumdas, R., Sarangapani, C., & Annapure, U. S. (2014). Cold plasma: a novel non-thermal technology for food processing. Food Biophysics, 10, 1–11.