Application of electrical impedance spectroscopy for the characterisation of yoghurts

Abstract

Electrical properties can provide information about food composition and structure. In this context, the present work aimed to characterise and group five samples (A, B, C, D, E) of low-fat, high-protein commercial yoghurts using electrical impedance spectroscopy (EIS) and conventional analytical techniques (rheological and physicochemical). The impedance analysis was performed in an experimental electrical system with frequencies ranging between 50 Hz and 1 MHz. Based on the results, samples were distributed into two main groups. The first, formed by yoghurts C and D, and the second group, composed by samples A, B and E. Pearson's correlation indicated that there is a positive linear correlation only between the absolute impedance of the samples in average (80 kHz) and high frequency (1000 kHz) and the rheological parameter k . Finally, the results suggest that EIS is a promising method for the assertive characterisation and grouping of yoghurts.