Dielectric properties of chili powder in the development of radio frequency and microwave pasteurisation

ABSTRACTFood products are dielectric materials. The ability to store and dissipate electromagnetic energy of food in dielectric heating is determined by its dielectric properties. To develop pasteurisation protocols based on radio frequency (RF) and microwave (MW) heating of chili powder, dielectric properties of chili powder were measured using an open-ended coaxial-line probe and an impedance analyzer over a frequency range from 8 to 3000 MHz. Penetration depth of chili powder was calculated at five selected frequencies. Results showed that the dielectric properties of chili powder decreased with increase in frequency from 8 to 3000 MHz, but increased with increase in moisture content from 4 to 15% (w. b.) and with increase in temperature from 25 to 85°C. Dielectric constant and loss factor of different density samples showed little difference at low temperature, but large difference at high temperature. RF waves have larger penetration depth in chili powder than MW, and therefore could result in better...