Rapid Measurement of Yeast Status using the Phase Angles of Harmonics in the Electrical Response Waveform

Abstract

We assessed the time dependence of the difference between living and dead yeast suspensions, in terms of the amplitudes and phase angles of their harmonics, when an alternating current (AC) voltage was applied to a yeast suspension. The measurements were repeatable and it was possible to accurately and quickly determine yeast status (living or dead) even within 1 s by reference to the phase angles of the 3rd harmonic. We found that measuring the phase angle of a dead yeast suspension in the system in advance permits us to distinguish between living and dead yeast without the need to calculate their relation to fundamental components such as the amplitude. This method based on the phase angles of harmonics is a powerful and convenient technique for quickly determining the status of yeast. These nonlinear responses change due to the presence of yeast itself and the collection of data on them including phase angles helps us to understand the electrical properties of cells.