A new approach to microwave food research: Analyzing the electromagnetic response of basic amino acids

Measurement of the electromagnetic properties of food is important for its electromagnetic protection, microwave heating and sterilization. Much research had focused on describing the non-thermal mechanism of electromagnetism and locating its site of action. Amino acids are the basic units of proteins, and therefore their electromagnetic characteristics are central to understanding the transmission and loss of microwave energy in food and the non-thermal mechanism of electromagnetic effects. Herein, the dielectric properties and conductivity characteristics of solutions of basic amino acids, at an electromagnetic frequency of 2.45 GHz and at temperatures between 10 °C and 70 °C, have been measured. The results show that the dielectric constant and dielectric loss decrease with increasing temperature, for example, increase the temperature form 10 °C to 70 °C, the dielectric constant of lysine at 2% decreased from 77.259 to 68.601, and the dielectric loss decreased from 13.412 to 10.302, due to the decrease of the solution viscosity and the relaxation time, causing an increase of the dipole moment. Increasing the concentration of the basic amino acids leads to an increase of the dielectric loss, fix the temperature at 20 °C, the concentration of lysine increased from 0.5% to 10%, the dielectric loss increased from 10.191 to 23.232, which is related to the change of the conductivity. The conductivity has positive correlation with the concentration and temperature of the amino acid solution, fix the temperature at 20 °C, the concentration of lysine increased from 0.5% to 10%, the conductivity increased from 234 to 2840 μS/cm, and when the temperature was increased form 10 °C to 70 °C, the conductivity of lysine at 2% increased from 694 to 1347 μS/cm. The absorption properties of the solutions are characterized by the loss of reflection, and the absorption characteristics of the basic amino acids are related to the electromagnetic frequency, the concentration and the thickness of the absorbing layer, the variation of which affects the impedance matching. In this paper, through the study of the electromagnetic characteristics of basic amino acids in solution, a theoretical basis for the application of basic amino acids in microwave sterilization, as well as a mechanism for the microwave effect, are proposed.