Basic Physical Principles - Broadband Reflectometry for Enhanced Diagnostics and Monitoring Applications - page 22

In particular, the estimation of the Cole-Cole parameters of foods (e.g., egg white,
butter, bacon, etc.) has received considerable attention, thanks to the possibility of
associating the dielectric parameters to the quality status of the products/materials
[23, 22, 21].
As a matter of fact, the evaluation of such parameters is not always a straight-
forward task, especially when dealing with complex materials, such as mixtures,
powders, etc..
For the sake of example, Table 2.2 shows the Cole-Cole parameters for some
common liquids, as reported in [11]. The Cole-Cole parameters of these and of other
liquids are typically used as reference for calibrating and validating experimental
setups for dielectric measurements. Fig. 2.9 shows the complex dielectric spectrum
of water, as reported in [18].

Ta b l e 2 . 2 Values of the Cole-Cole parameters for some common liquids, as reported in [11]

τ =

/ (

π f r )

material ε s ε ∞ 1 2 β

(ps)

air 1.0005

chloroform 4.82 2.28 6.25

ethyl-acetate 6.04 2.48 4.4 0.06

toluene 2.40 2.25 7.34

Fig. 2.9 Complex dielec-
tric spectrum of water at
20 ◦ C. The dashed line indi-
cates the extrapolated high
frequency permittivity, ε ∞ ,
of the principal relaxation
of water. The dotted line
shows the extrapolated high
frequency permittivity of
an additional relaxation,
with relaxation frequency
1 / 2πτ − 1 , around 1000 GHz
[18]