Contactless Radio Frequency Monitoring of Dielectric Properties of Egg White During Gelation

The evaluation of dielectric properties in the radio frequency (RF) bandwidth is highly relevant to characterize the physical or physiological state of organic materials. This paper reports on the implementation of an easy-to-use and contactless RF dielectric sensing technique used for the monitoring of the heat-induced gelation of a white egg sample. The sensing technique basically consists in the distant monitoring of a high-quality factor inductive RF resonator operating at 98 MHz, which is electromagnetically coupled to the egg white sample. A lumped element modeling of the contactless RF probe interacting with the egg white is proposed. It is used to estimate both the conductivity and the permittivity of the sample during its gelation, starting from the impedance changes measured at the ends of the RF probe, and after probe calibration carried out using a reference NaCl solution. The results obtained during a 10 h monitoring experience allow the dynamics of the egg white gelation to be analyzed. These results open the way to the development of easy-to-implement and non-invasive dielectric monitoring of organic materials, with many prospects in agrifood as well as health monitoring applications.