Dielectric spectroscopy of Baijiu over 2–20 GHz using an open-ended coaxial probe

The complex electric permittivity of Baijiu (one of the most consumed beverages) is measured over a frequency range of 2 to 20 GHz using a low-cost open-ended coaxial probe and a portable microwave analyzer. The Cole—Cole equation is used to fit the permittivity data, and the parameter values related are extracted using the particle swarm optimization. A linear relationship is obtained between these parameters and the alcohol by volume. A strong dependence of the permittivity on the alcohol content is also observed for other alcoholic drinks, including brandy and whisky. The study demonstrates that the microwave technique provides an efficient solution in the effort to determine the alcohol content and the principal component analysis is a powerful tool for the quick estimation of the dielectric properties. The sensor presented can contribute to efficient on-site quality control of alcoholic drinks.