Oscillating Magnetic Field
- 1. Oscillating Magnetic Field Presented by Prasanna Bhalerao Dipak Gujar 17 FET 402 17 FET 501 Institute of Chemical Technology, Mumbai
- 2. Introduction Oscillating magnetic field is used to inactivate microorganisms. Improves the quality and shelf life compared to other conventional process. OMF affects 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.
- 3. Magnetic Field MagneticField:Measuredintermsofmagnetic intensityB. Magnetic field may be homogenous or heterogeneous Homogenous: Field Intensity B is uniform. Heterogeneous: Field Intensity is non uniform Telsa:Unit to expressmagnetic flux density (B). Fig: Magnetic Field
- 4. Generation of high intensitymagnetic 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: - superconductingcoils - coils that produce DCfields - coils energized by the discharge of energy stored in capacitor. Fig: Oscillating Magnetic Field
- 5. Magnetic fields with intensities up to 3T can be generated by inserting an iron core in thecoil. If T is >3 magnetic saturation occurs and produces Joule heat and causes large power consumption. Air core solenoids are usedtoobtain high magnetic field intensities. Super conducting magnets can generate high intensity magnetic field without anyjouleheating .
- 6. Inactivation of Microorganism Yoshimura (1989) classified the effects of magnetic field on microbial growth and reproduction as i) inhibitory, ii) stimulatory, and iii) none observable. Hoffman (1985) reported inactivation of microorganism with OMF in milk, yogurt, orange juice and bread roll One pulse of OMF was adequate to reduce the bacterial population between 102 and 103 cfu/g.
- 7. Mechanism of OMF • The first theory stated that a "weak" OMF could loosen the bonds between ions andproteins. • Anion entering amagnetic field Bat velocity v experiences a force Fgiven by • F=qv * B,it is known asICRmodel. • The frequency at which the ions revolve in the magnetic field is known as the ion's gyro frequency , denoted by‘n’. • 'n’ depends on the charge/mass ratio of the ion and the magnetic field intensity.
- 8. When vand Bare parallel, Fiszero.When v isnormal to B,the ion movesin a circular path. • For other orientations between v and B, the ions move in a helical path. Charged particle in a magnetic field when v is normal to BV: Velocity of Charged Particle B: Magnetic Field
- 9. Fig. Cascade of responses in a biological cell exposed to magnetic field The interaction sites in the magnetic field are the cell tissues most affected by the magnetic field Fig. Intensity of response in regions 1, 3, and 5 in Figure 8. Q1 > Q3 > Q5.
- 10. Exposure to low intensity electric and magnetic fields. • Variables: magnetic flux densities of the AC and Dc magnetic field, Ac frequency and charge to mass ratio • Principle: Interaction of specific ions with biological matrices. • Mode of Action 1. Loosening bonds between ions and Protein 2. Damage to Calcium and Magnesium ions (tissues and organs) 3. Breakdown of Covalent bonds in DNA IPR Model
- 11. Magnetic field andmicroorganisms magneto tactic bacteria tend to move along lines of magnetic field. They might be Gram Positive or Gram Negative. Magnetosomes in the bacteria helps to migratetheir position. Fig: Magnetotactic bacteria Fig: Magnetic Field
- 12. Effect of OMF on Microorganisms
- 13. Critical Process Factors 1. Magnetic Field: Stimulate or inhibit growth and reproduction of MO. High Intensity Magnetic Field (HIMF) affects membrane fluidity. 2. Electrical Resistivity: Depends upon applied magnetic field and thickness of food. It needs to be in range >10-25 ohms-cm. 3. Process Deviation: Proper maintenance of power source, number of pulses, frequencies applied, food composition, size of unit
- 14. Applications OMF used for Solid as well as liquid foods. Range 1-100 pulses, 5-500 kHz, Temp: 0-50°C, Time 25-100μs Frequency >500 kHz less effective in microbial inactivation and tend to heat the food material (Barbosa-Canovas et al., 1998) Temp increase 2-5°C OMF: intensity 5-50 T, Frequency 5-500 kHz : 2 log reduction (Hoffman, 1985) OMF applied in the form of pulses , intensity of each pulse decreases by 10%
- 15. Research Gaps Theories of effect of magnetic field on microbial inactivation. Destruction kinetics of magnetic field Determination of critical process parameters and effects on microbial inactivation Process validation and evaluation of indicator organisms. Identification of Process deviation and ways to address them
- 16. Conclusion • Reducedenergy requirements for adequateprocessing. • Potential treatment of foods inside a flexible film package to avoid post processcontamination. • 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 bestudied in detail.
- 17. References Nuria Grigelmo-Miguel et al., (2011), Use of Oscillating magnetic field in food preservation, Non-Thermal Processing Technologies for Food, Blackwell Publishing Ltd, pp. 222-235. Gustavo Barbosa et al., (2000), Oscillating magnetic field, Journal of Food Science, 65, 86-89.
- 18. Thank You