  A detailed knowledge of the dielectric properties of food materials is vital
to any electromagnetic-based treatments, ranging from reheating meals in a
domestic microwave oven through to sterilization processes. The uniformity and
rate of heating of the food is highly dependent upon the dielectric constant
and dielectric loss of the food material, with both parameters being
intrinsically temperature-dependent. In this work, we explore various methods
for the dielectric characterisation of materials over a wide frequency range (1
MHz to 20 GHz), to cover RF and microwave frequencies, as well as understand
the impact of ingredients (e.g. salt, sugar) and temperature on free and bound
water resonances. Such a large frequency range gives information that is
invaluable when designing future equipment that relies on
multi-frequency/broadband microwave heating techniques. The characterization
methods of interest are the open-ended coaxial dielectric probe, the broadband
dielectric broadband spectrometer, and a custom stripline resonator. Instant
mashed potato is used as a food standard, which allowing for a large set of
samples to be measured with various moisture contents. When directly compared
at 1 GHz, all three methods produced comparable dielectric properties for 20%
and 30% potato mixtures.
