Non-contact Assessment of Apple Condition using Magnetic Induction Spectroscopy: Preliminary Results and Indications

Bioimpedance spectroscopy is the electrical impedance of a biological sample measured over a range of different frequencies. Over the kHz to MHz range, the characteristic shape of the spectra is denoted as the β dispersion, and is the result of the polarisation of cell boundaries presenting a capacitance that contributes to the overall flow of electrical current in the sample. This implies that the curve of the dispersion could be a marker for breakdown behaviours and cell vitality within the fruit, as variations in the cell walls (looseness or cell death) will present different overall capacitances. In this paper, we present some early results exploring the relation between the bioimpedance spectra and variations in the fruit quality of apples, caused by different growing conditions, irrigation, stress, and injury. We use a novel measurement technology termed Magnetic Induction Spectroscopy which uses magnetic fields and induced eddy-currents to ascertain a relative conductivity measure over a frequency range from 50 kHz to 2.5 MHz. The significant advantage of this approach is that it is non-contact, opening the possibility of future in-field or process-line operation.