Dielectric properties of litchi fruit ( Litchi chinensis Sonn) at microwave frequencies

The dielectric properties of litchi fruit were determined using the open-ended coaxial probe method. The measurements were performed in the frequency range from 0.5 to 20 GHz during 3 days of storage at room temperature (~ 24 °C). The dielectric properties increased with storage time. Additionally, measurements at different temperatures (24, 30, 40 and 50 °C) were determined. The dielectric constant ( ε ′) decreased with increasing temperature in a frequency range of 0.5–5 GHz; at higher frequencies, ε' increased with increasing temperature. The loss factor ( ε ″) value increased at frequencies higher than 2 GHz and decreased with increasing temperature. The results will be useful for further applications using microwaves, such as microwave-assisted drying, sensing of quality parameters, modeling, and heating to protect against molds or insects, among other applications.