The object of the study is bioelectrical impedance as an indicator of the degree of tissue destruction and a tool for analyzing the nature of structural deformations. The subject of the study includes transformations of impedance spectra and corresponding electrical equivalent circuits under the influence of aggressive factors, the effect of various degrees of destruction on circuit parameters, and the frequency dispersion of complex electrical characteristics. Complementary and cross-validating methods were employed, including impedance spectroscopy, optical microscopy, the Cole–Cole method, and mathematical processing and visualization of experimental data (ZView, Origin). Experimental measurements were performed using an Autolab PGSTAT impedance spectrometer, a Micros Austria MC300 optical microscope, and a ToupCam 5.1M UHCCD Sony digital camera with a ToupTek Photonics AMA075 adapter (ToupView v.3 software). An optimized methodology for obtaining tissue impedance spectra under laboratory conditions was developed. The design of measuring cells was proposed, and geometric parameters of intact and experimental samples were established to ensure reproducible and high-quality spectral data. Based on Nyquist plots, the structure of electrical equivalent circuits was determined and their transformations under destructive influences were analyzed. A probable correspondence between equivalent circuit elements and tissue structural components was established. It was shown that increasing temperature and exposure time lead to a decrease in the real and imaginary parts of complex impedance, accompanied by reductions in resistance and capacitance. At temperatures approaching denaturation thresholds, the electrical equivalent circuit loses the CPE–R branch, indicating irreversible structural damage. Destruction of the plasma membrane initiates a transition from an anisotropic to an isotropic state, resulting in increased conductivity due to enhanced ion mobility. Temperature rise is also associated with an increase in the dielectric loss tangent and resonance frequency, attributed to an increased number of effective dipoles. Repeated exposure to specific frequency ranges, particularly 100 kHz, may induce structural alterations in the cell membrane. The position of frequency maxima shifts depending on sample size and structural condition, whereas the minimum near ~1 Hz remains stable and may serve as a marker of transitions between conductive regimes. The obtained results provide a basis for applying impedance-based approaches in non-invasive diagnostics of tissue damage (burns, ischemia, necrosis), assessment of biomaterial viability, and monitoring of thermal or chemical treatment efficiency. Novelty: For the first time, the regularities of transformation of impedance spectra of biological tissues with different morphology under the influence of temperature, exposure time, and repeated measurements have been established, and it has been shown that these changes are reflected in the restructuring of the corresponding electrical equivalent circuits, in particular in the loss of CPE–R branches at temperatures approaching membrane protein denaturation. The structure of multi-element equivalent circuits for intact and damaged tissues has been substantiated, and informative parameters (R, CPE-T, frequency extrema) sensitive to the degree of structural degradation have been identified. Temperature–time and geometric regularities in the variation of complex impedance have been revealed, associated with membrane integrity disruption and transition to a more isotropic conductive state. Practical significance: The study develops a structure-sensitive approach to the analysis of impedance spectra and optimizes the methodology of ex vivo measurements, ensuring reproducibility of results. The proposed approach can be applied for quantitative assessment of tissue damage and for the development of diagnostic and monitoring systems based on impedance spectroscopy. Field of application: medicine, gastronomy.
