Temperature-dependent dielectric properties of honey associated with dielectric heating Original Research Article

Dielectric properties of pure yellow-locust and jujube honey and their water solutions at seven final water content levels from 17.4% to 42.6% were measured with an open-ended coaxial-line probe from 10 to 4500 MHz at 20–80 °C. The results showed that the dielectric constants of pure honey increased with increasing temperature when frequency was above 40 MHz. For honey solutions, the dielectric constant decreased with increasing temperature at the lower frequencies, but increased at the higher frequencies. At any given water content, the relaxation frequency shifted to a higher frequency with increasing temperature, while the loss factor peaks showed little change. There was a strong negative linear correlation between penetration depth and frequency in log–log plot for pure honey at 20–80 °C. The research will be helpful in developing effective honey pasteurization processes with radio-frequency and microwave dielectric heating.