## 3 Results and Discussion
Since the aggregation process of casein micelles has not yet been extensively investigated by dielectric measurements, and comparative analysis of rheological and dielectric properties has not been carried out at all, the method we applied is positively worth investigating--especially because of the numerous advantages of dielectric assessment (low costs, non-damaging, requiring no sample preparation, etc.) over the aforementioned analytical methods. To determine the correlation between the changes in viscosity and the dielectric constant, we established a logarithmic-transformed linearized function between these two values, i.e., depicted the dielectric behavior in the function of the parameter that describes the change in material structure (viscosity). Using this method, we can analyze whether the structural change is also reflected in the change in the dielectric behavior. Since the time-dependent dynamics of the whole process can be split into two distinct phases (10-25 min, 30-60 min), and because there is a slight shift between the maximum point of the dielectric constant and the apparent viscosity (25 min vs. 30 min), we depicted these phases separately (in the first 10 min, no observable difference is shown for the values of viscosity; therefore, the correlation analysis is not applicable). Figure 3a shows the data obtained for the 10-25 min interval, and Figure 3b for the 30-60 min interval (second phase of coagulation). Based on the values of the coefficient of determination calculated for each phase of the coagulation process (R\({}^{2}\) = 0.9655 and 0.922, respectively), it can be stated that there is a strong correlation between the apparent viscosity of the inoculated milk sample and its dielectric behavior. On the one hand, this indicates that the measurement of the dielectric constant can be used to predict or verify the point of clot formation, even on an industrial scale. The use of measurement methods based on dielectric properties can be advantageous to the measurement of viscosity in more than one way, e.g., it does not alter or break the structure of the investigated material, is easier to automatize, using multiple sensors is more easily implemented, and the obtained values are basically independent of the measurement circumstances (except for temperature, of course). On the other hand, these experimental findings strongly support the idea that the chemical, biochemical, and physical processes that involve the transformation of molecular components can be monitored by measuring the dielectric behavior of the investigated media since the dielectric properties--aside from the temperature and the frequency--mostly depend on the physical and (bio)chemical structure and composition of the materials. [PERSON] et al. studied the viscosity and dielectric properties of edible oils and concluded that the strong correlation of viscosity with dielectric loss tangent enables the assessment of the quality of oils based on the analysis of dielectric behavior [29]. In the second part of our experiments, we investigated the acid coagulation of the raw milk sample that originated from the same place. The main distinct difference between the two processes is that during acid coagulation, the applied microbial strains (_Lactobacillus delbrueckii_ and _Streptococcus themophilus_, in our case) break down the lactose content of the sample, converting it into lactic acid, which lowers the pH of the medium. When the pH reaches the isoelectric point of the casein micelles (pH = 4.5-4.6), the net surface charge becomes zero, and, therefore, the electrostatic repulsion no longer persists, which will eventually cause the casein micelles to aggregate [30]. As in the previous series of experiments, firstly, we investigated the dynamics of the apparent viscosity and dielectric constant of the fermentation process in the function of time.