The presentation discusses the working mechanism, applications along with research gap.

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