## 1 Introduction
The relationship between the electric field strength and the electric shift is given by the absolute permittivity (\(\varepsilon\)) of the materials:  
\[\varepsilon=\frac{E}{D} \tag{1}\]  
Absolute permittivity is a constant that depends on the quality of the material and is, in fact, a measure of the extent to which the material \"responds\" to the electromagnetic field strength. For homogeneous, isotropic media (i.e., in which the magnitude of the different physical quantities is the same in all three directions of space), absolute permittivity can be defined as a linear scalar quantity, whereas for anisotropic materials, it can be interpreted as a homogeneous linear mapping of the vector-vector type, i.e., as a second-order tensor. The dielectric shift \(D\) in real materials also depends on the polarizability of the system. The relationship between the two can be written using the Clausius-Mosotti relation [14]:  
\[D=\varepsilon_{0}E+P=\varepsilon_{0}(1+\chi)E \tag{2}\]  
Since the response of real materials to the electric field \(E\) is delayed in time, the dielectric shift \(D\) is also delayed, which can be understood as a kind of phase shift (8). The magnitude of the phase and the phase itself can only be expressed in exact terms using complex numbers, so it is useful to express the permittivity of a given medium or material as a complex function of the frequency of the applied electromagnetic field, where \(\varepsilon^{*}\) is the complex permittivity:  
\[\varepsilon\to\varepsilon^{*}(f) \tag{3}\]Such as any other complex function, the complex permittivity can also be separated into its real and imaginary parts:  
\[\varepsilon^{\ast}(f)=\varepsilon^{\prime}(f)-i\varepsilon^{\prime\prime}(f);\;i= \sqrt{-1} \tag{4}\]  
The real part of the function is called the dielectric constant (\(\varepsilon^{\prime}\)), while the complex part is called the dielectric loss factor (\(\varepsilon^{\prime\prime}\)). As can be seen from the equation above, these two quantities are frequency dependent, i.e., for a given material, their values vary as a function of frequency. From an electrodynamic point of view, the dielectric constant indicates how much of the energy conveyed by the electromagnetic field can be absorbed and stored by the material interacting with it, while the loss factor expresses how much of the stored electrical energy is converted into other types of energy (such as heat or kinetic energy). The applicability of dielectric measurements in various scientific and industrial fields has long been addressed in the literature, including their implementation in a wide variety of technological processes in the food industry, with a particular focus on dairy processes. In a 2014 study, [PERSON] et al. investigated the frequency and temperature dependence of the dielectric behavior of raw cow milk and goat milk for the optimization of a microwave heat treatment process. Based on the analysis of dielectric constant, loss factor, and penetration depth, they concluded that the loss factor decreased with increasing temperature at a frequency of 2.45 GHz, i.e., a more homogeneous temperature profile can be achieved with microwave irradiation at this frequency over a higher temperature range [15]. In a 2018 study, [PERSON] et al. investigated the dielectric parameters of distinct types of milk (raw, skimmed, and condensed fat-free) when heated to ultra-high temperatures at frequencies between 10 and 2450 MHz. The research results showed that the dielectric parameters (\(\varepsilon^{\prime}\) and \(\varepsilon^{\prime\prime}\)) of cow's milk at temperatures above 100 \({}^{\circ}\)C need to be investigated in order to evaluate the sterilization of milk based on dielectric heating [16]. It was found that the dielectric constant (\(\varepsilon^{\prime}\)) decreased with frequency at all temperatures but increased with temperature at low frequencies and decreased with temperature at high frequencies.