Oscillating magnetic field for food processing
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The document discusses the use of oscillating magnetic fields (OMF) for inactivating microorganisms in food processing, emphasizing its potential to improve food quality and shelf life. It covers the mechanisms of OMF, including the impact on cell membranes and the biological response of microorganisms, as well as the technical aspects of generating high-intensity magnetic fields. The conclusion highlights OMF's advantages in food preservation, such as minimal nutrient loss and reduced energy requirements, while also noting the need for further research on its effects and mechanisms.
Oscillating magnetic field for food processing
- 1. Oscillating magnetic field for food processing Department of agriculture and food engineering IIT Kharagpur Praveen Kumar
- 2. Introduction • The utilization of oscillating magnetic field to inactivate microorganisms. • OMF has the potential to improve the quality and shelf life compared to other conventional process. • OMF effects the microorganisms, cell membranes, malignant cells and the potential application of magnetic field for food preservation. • OMF of intensity of 5 to 50 telsa (T) and frequency of 5 to 500 kHz was applied and reduced the number of microorganisms by at least 2-log cycles. • Magnetic fields increase DNA synthesis .
- 3. Mechanism of OMF & ICR model • The first theory stated that a "weak" OMF could loosen the bonds between ions and proteins. • An ion entering a magnetic field B at velocity v experiences a force F given by F = qv * B, it is known as ICR model. • When v and B are parallel, F is zero. When v is normal to B, the ion moves in a circular path . • For other orientations between v and B, the ions move in a helical path . • The frequency at which the ions revolve in the magnetic field is known as the ion's gyro frequency , denoted by ‘n’. • Which depends on the charge/mass ratio of the ion and the magnetic field intensity.
- 7. Magnetic field • The region in which a magnetic body is capable of magnetizing the particles around is called the magnetic field . • Isotropic susceptibility and anisotropic susceptibility of magnetization. • Magnetic field is measured in terms of magnetic intensity B. • Diamagnetism and paramagnetic property of magnet. • Magnetic fields are homogeneous and heterogeneous in nature.
- 9. Key at a glance • Cyclotron resonance : Phenomenon that occurs when the frequency of revolving ions induced by a specific magnetic field intensity is similar to the frequency of that magnetic field and parallel to it. In these instances, energy may be transferred to the ions, affecting cell metabolic activities. • Cyclotron. An accelerator in which particles move in spiral paths in a constant way. • Dipole. For oscillating magnetic fields, a magnetic particle that contains a *north* and *south* magnetic pole. • Magnetic flux density. Force that an electromagnetic source exerts on charged particles. Magnetic flux density is measured in Telsa (1 Telsa =104 gauss).
- 10. Key at a glance • Oscillating magnetic field: Fields generated with electromagnets of alternating current. The intensity varies periodically according to the frequency and type of wave in the magnet. • Sinusoidal Wave: A mode of propagation of the magnetic field. • Static magnetic field: Magnetic fields with a constant strength over time. • Telsa: Unit to express magnetic flux density (B). 1 Telsa (T) = 104 gauss.
- 11. Electrical resistivity • For microorganisms to be inactivated by OMF, foods need to have a high electrical resistivity (greater than 10 to 25 ohms- cm). • The applied magnetic field intensity depends on the electrical resistivity and thickness of the food being magnetized, with larger magnetic fields intensities used with products with large resistivity and thickness.
- 12. Microbial growth stage • Tsuchiya and others (1996), working with homogeneous (7 T) and inhomogeneous (5.2 to 6.1 T and 3.2 to 6.7 T) magnetic fields, found a growth stage dependent response of Escherichia coli bacterial cultures. • The ratio of cells under magnetic field to cells under geomagnetic field was less than 1 during the first 6 h of treatment and greater than 1 after 24 h. • Cell survival was greater under inhomogeneous compared with homogeneous fields. • The magnetic fields could act as a stress factor, cells collected after 30 min of incubation under magnetic field treatment (lag or early lag growth phase) or in the stationary phase after long-term magnetic field treatment were heated to 54 oC .
- 13. Process Deactivation • Data acquisition systems must be installed in the processing area to monitor and control the power source, number of pulses, and frequencies applied to the food. • Food composition, temperature, size of unit, among other factors also would require control and monitoring to assure constant treatments. • Any deviation from the specified conditions such as temperature changes must be continuously recorded and appropriate responses must be taken.
- 14. Generation of high intensity magnetic fields • Magnetic fields are usually generated by supplying current to electric coils . • The inactivation of microorganisms requires magnetic flux densities of 5 to 50 telsa(T). • OMFs of this density can be generated by using following methods : - superconducting coils - coils that produce DC fields - coils energized by the discharge of energy stored in capacitor .
- 15. • Magnetic fields with intensities up to 3 T can be generated by inserting an iron core in the coil. • Above 3 T, insertion of iron core is not useful because of the magnetic saturation in the core , therefore, air core solenoids are used to obtain high magnetic field intensities . • Joule heat produced creates problem and large power consumption. • Super conducting magnets can generate high intensity magnetic field without any joule heating .
- 16. Circuit for magneform 7000 series coil
- 18. Magnetic field and microorganisms • Aquatic bacteria known magneto tactic bacteria tend to move along lines of magnetic field and are accordingly influenced by the earth’s magnetic field. • In the absence of any other magnetic field except the geometric field, the magneto tactic bacteria migrates northward. • The presence of magnetic particles called magnetosomes in the bacteria helps to migrate northwards. • Magneto tactic bacteria are genetically capable of synthesizing magnetosomes from available iron .
- 19. • By convention the direction of magnetic field is the one indicated by the north seeking end of a magnetic compass needle. • Accordingly the earth’s magnetic field points up at the south pole, down at the north pole and horizontal ally northward at the equator. • Therefore, in the northern hemisphere the north seeking bacteria migrate downward and the south seeking bacteria migrate upward .
- 21. Magnetic fields tissues and membranes • Biological membrane exhibit strong orientation in a magnetic field because of the intrinsic anisotropic structure of the membrane . • Orientation of cell membrane parallel or perpendicular to the applied magnetic fields depends on the overall anisotropy of the bio molecules such as protein associated with membrane . • The peptic bond in the protein molecules resonating between two structure exhibits diamagnetic anisotropy . • Therefore, orientation parallel to an external magnetic field , as does the plane of the carbon – carbon double bond.
- 22. Magnetic fields and malignant cells • Animal or animal body parts affected with malignant cells are placed in magnetic field and subjected to a total of 1 to 1000 pulses. ( tumor with 10 pulses in 1000 micro sec ). • OMF reduces the cell population below a threshold concentration . • The tumor diminishes in size than the untreated tumors . • No heat is generated in the body due to exposure of magnetic field . • Magnetic field causes less damage to the natural immune system of the body the ionizing irradiation .
- 23. Magnetic fields in food preservation • Food preservation methods alter the nature of the food and impart undesirable characteristics . • OMF technique is useful in activating the microorganisms after the desired fermentation . • A single pulse with a flux density between 5 to 50 T and frequency 5 to 500 kHz reduces the number of microorganism by 2 log cycles . • This technology used can improve the quality and increase the shelf life of pasteurized foods. • Electrical resistivity is vital for food preservation using magnetic field technology many foods posses this property.
- 24. • The applied magnetic field intensity is a function of the electrical resistivity and thickness of the food being magnetized . • Preservation of foods with magnetic field involves sealing the food in a plastic bag subjected to 1 to 100 pulses , frequency 5 to 5000kHz and temperature 0 to 50 degree Celsius, exposure time 25 micro sec to 10 mille sec. • No special preparation of food is required before treatment of the food by OMF. • Higher frequencies 500 kHz and above are less effective for microbial inactivation and heat the food product.
- 25. conclusion • The technological advantage of inactivating microorganisms with OMFs include, minimal thermal denaturation of nutritional and organoleptic properties. • Reduced energy requirements for adequate processing. • Potential treatment of foods inside a flexible film package to avoid post process contamination. • Additional research is necessary to correlate the inactivation of microorganisms in food and techniques . • The effects of magnetic fields on the quality of food and the mechanism of inactivation of microorganisms must be studied in detail.
- 26. References • Barbosa-Cánovas, G.V., Pothakamury, U.R., and Barry, G.S. 1994. State of the art technologies for the stabilization of foods by non-thermal processes: physical methods. In: Barbosa-Cánovas, G.V., and Welti-Chanes, J.(eds.), Food Preservation by Moisture control. Lancaster, Technomic Publishing.pp. 423-532. • Barbosa-Cánovas, G.V., Gomorra-Nieto, M.M., and Swanson, B.G. 1998. Nonthermal electrical methods in food preservation. Food Sci. Int. 4(5):363-370. • Coughlan, A., Hall, N. 1990. How magnetic field can influence your ions? New Scientist. 8(4):30 • Frankel, R. B. and Liburdy, R. P. 1995. Biological effects of static magnetic fields. In Handbook of Biological Effects of Electromagnetic Fields. Polk, C. and Postow, E. (Ed). 2nd Ed. CRC Press. Boca Raton, FL • Gerencser, V.F., Barnothy, M.F., and Barnothy, J.M. 1962. Inhibition of bacterial growth by magnetic fields. Nature, 196:539-541. • Gersdorf, R., deBoer, F.R., Wolfrat, J.C., Muller, F.A., Roeland, L.W. 1983. The high magnetic facility of the University of Amsterdam, high field magnetism. Proceedings International symposium on High Field Magnetism. Osaka, Japan. 277- 287 • Hofmann, G.A. 1985. Deactivation of microorganisms by an oscillating magnetic field. U.S. Patent 4,524,079. • Kimball, G.C. 1937. The growth of yeast on a magnetic fields. J. Bacteriol. 35:109- 122.
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