## 5 Conclusions  
In this research work, the feasibility of monitoring the antisolvent crystallization of sucrose using electrical impedance spectroscopy (EIS) was studied at laboratory scale. Herein, the impedance spectra of the ternary solutions of sucrose-water-ethanol acquired by 1-D thin electrodes were used to create a frequency response model. The parametric model was further developed to estimate a series of transfer functions of the measured impedances. According to the results, the experimental dataset of the ternary solutions in the frequency range of 50-300 kHz was in good agreement with a transfer function model containing two poles and a single zero (Model 3). This was established using a quantitative analysis performed by estimating the normalized root mean squared Error (NRMSE) measure to evaluate how well the response of the model fits the experimental data. The proposed approach has possibilities to detect the impedance variation according to concentration ratio during the crystallization process. The analysis of the model constants indicates a dependence between the concentration of the constituent component and the poles and zeros of the model (EIS measurements). In future studies, more complex component analysis can be carried out to limit the variable space and identify the behaviour of the impedances for a given operating condition during the antisolvent crystallization.  
Furthermore, a 2-D electrical resistance tomography (ERT) system with a low conductivity sensor unit was designed and tested with demineralized water, tap water and industrial food grade saturated sucrose solution. Low conductivity region of sucrose particles concentration was observed and reconstructed in real-time using Bayesian reconstruction methodology. This study provides the possibility of utilizing the EIS and ERT as complementary PAT methods to control sucrose manufacturing. Upon future investigations, additional development of these process monitoring modalities with different conductivity profiles could provide a multi-frequency ERT sensor that can be applied for antisolvent crystallization process monitoring and quality assurance. A multi-sensor based semi-empirical approach for monitoring status, application of control, and visualization of the distribution of crystalline solids are foreseen.  
Conceptualization, G.R., L.J.-S., T.K. and S.A.; methodology, G.R., S.A., L.J.-S., and T.K.; software, R.W.; validation, G.R. and L.J.-S.; formal analysis, G.R.; investigation, G.R. and S.A.; resources, R.W. and T.K.; data curation, G.R. and S.A.; writing--original draft preparation, G.R.; writing--review and editing, G.R., S.A., and L.J.-S.; supervision, L.J.-S. and T.K. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 764902\".  
We would like to thank the chemical engineering department at Lappeenranta university of technology for their access to the laboratory. I would like to thank Roscole company for their constant support in the manufacturing and design of the signal conditioning units and support and training for the utilization of the Roc-GUI software interface.  
The authors declare no conflict of interest.