Impedance spectroscopy method used for the unpasteurized beer microbiological contamination degree assessment

The main aim of the below presented work was to investigate the possibility of using impedance spectroscopy in the unpasteurized beer microbial contamination degree assessment. Advantages of the impedance spectroscopy method, a negligible number of similar published results as well as their practical aspect make the research important. Four different types of beers were investigated which were unfit for consumption due to improper storage and were heavily microbiologically contaminated. Their impedance was measured in the frequency range from 0.1 Hz to 1 kHz before and after centrifugation. Based on the measured values, an innovative electrical equivalent circuit was proposed and the parameters of the circuit elements were fitted. The obtained results show significant differences (23 up to 35%) in the values of resistance modelling the diffusion phenomenon. Such large changes, resulting from the removal of biomass from the samples, prove the validity of impedance spectroscopy in the study of the properties of unpasteurized beer. According to the authors, it would be possible to use the proposed methodology during the production of beer. With some limitations, it should aid in the early detection of microbial contamination.