Dielectric properties of starch slurries as influenced by starch concentration and gelatinization

Dielectric properties of corn starch slurries of 10–50% (w/w) starch concentration were measured at temperatures between 40 and 90 °C and in the frequency range from 15 MHz to 3 GHz. Dielectric constant decreased and the loss factor increased with increasing starch concentrations. The dielectric loss factor of the starch slurries decreased at frequencies 15–450 MHz and increased at frequencies 450 MHz to 3 GHz. A significant effect of frequency on the dielectric constant was evident only at higher starch concentrations (>40%). Dielectric constant of starch slurries decreased with increasing temperature throughout the frequency range while the dielectric loss increased with temperature between 15 MHz and 450 MHz and then decreased with increase in temperature between 450 MHz and 3 GHz. During gelatinization, the dielectric constant for 20% starch slurry decreased in a linear fashion. A significant correlation (R2 = 0.87611; P < 0.05) was observed between the dielectric constant and the percentage gelatinization for the 20% starch slurry in the temperature range from 60 to 72 °C.