Handbook of Meat Processing

Physical Sensors for Quality Control during Processing 447

ε (^) d ′′ represents the loss factor caused by the
dipolar orientation or dipolar relaxation.
ε (^) MW ′′ represents the loss factor due to the
Maxwell - Wagner effect.
ε (^) e ′′ represents the loss factor relative to elec-
tronic polarization.
ε (^) a ′′ represents the loss factor caused by
atomic polarization.
σ / ε 0 ω represents the loss factor due to the
effect of ionic conductivity, where σ , ε 0
and ω are the conductivity of the material,
the dielectric constant in vacuum, and the
angular frequency, respectively.

Electric Impedance Spectroscopy

(Bioimpedance)

The application of bioelectrical impedance

(electrical impedance in the medical fi eld)

brane surfaces, the active cell membrane
effects, and gated channels, caused mainly by
the intracellular structures or the ionic diffu-
sion (Grimnes and Gr ø ttem - Martinsen 2008 ).
In some cases, it could be useful to analyze
the energy dissipation of these relaxation
phenomena in terms of loss factor spectra
instead of conductivity spectra (Fig. 25.5 ).
Loss factor can be expressed by Equation
25.4 , which refl ects the different phenomena
contributing to the loss factor spectrum,
depending on the frequency range. It is
important to highlight that ionic conductivity
only introduces losses into the material when
exposed to electromagnetic energy.

εεε εε′′= ′′+ ′′ + ′′+ ′′+

σ

εω

dMWea

0

(25.4)

where:

Counterion

effect

e≤

db

dfw

106 109

Radio frequency

AC... L-M-Kwave VHF dm cm mm mm nm ...

Microwaves IR V UV X-rays

1012 1015

i

• 
  

  –

  
  


• 
  


• –


• 
  


• 
  


• 
  


• 
  


• 
  


• 
  


• – –


• 
  


• 
  


• 
  


• 
  


• 
  


• 
  


• 
  

+ +

+

+

+

+

a

e Electronic

level

changes

f (Hz)

ionization

MW

Figure 25.5. Schematic representation of the electromagnetic spectrum (in logarithm scale) of the different
effects that contribute to effective loss factor (adapted from Castro - Gir á ldez et al. 2008 ) , where i represent
the ionic losses; MW means Maxwell - Wagner effect; d fw is related to the dipolar losses of free water; d b is
related to the dipolar losses of bound water; a is related to the atomic losses; and e is related to the electronic
losses.