Equipment for the determination of dielectric properties of vegetable tissue during its mechanical loading

Abstract

The internal structures of agricultural products change substantially in the course of the products deformation. One of the main changes in this process is the loss of the water content and water solutions generally due to the squeezing out of the cellular sap. The water content can be detected also by electric conductivity measured at different frequencies. The precise measurement of the electric conductivity during the deformation of soft agricultural products can be used as a simple indicative method for the study of the processes that control the squeezing out of the cellular sap including the filtration abilities of the cellular walls. In the paper, the experimental equipment is described that is able to detect the impedance of the vegetable tissue specimens during their compression between two plates. The equipment determines the sample impedance from a direct measurement of three voltages in the circuit that contains the tested specimen. The equipment is able to analyse the specimen properties at more than ten different frequencies up to 1 MHz. The formulas for the calculation of the real and the imaginary components of the relative permittivity are also given.

Keywords

• soft plant tissue
• conductivity
• permittivity
• frequency
• deformation
• reversibility