FACTORS AFFECTING DIELECTRIC PROPERTIES OF THE SOUR CHERRY
(Prunus cerasus L.) POMACE FRACTIONS: FREQUENCY, pH, IONIC
SOLUTIONS, TEMPERATURE, CONCENTRATION, PARTICLE SIZE
Aim and Justification
The main objective of this study is to rework of sour cherry juice waste by formulating the
pomace-fortified products. The microbiological safety of the waste material is the priority of
the study. Dielectric heating is very popular application not only to bake the product but also
to decrease microbial load and pests in the materials (Wang et. al., 2003). Hence, the
dielectric properties of sour cherry pomace are required to treat it by using dielectric
technology.
Material
Sour cherry pomaces were tray-dried at 60°C for 6 h. Then, ground them for 60 seconds.
Following the sieve analysis, the fractions were encoded as 298-595, 150-297, 149-106, 75105 and <74 μm.
Methods
The dielectric properties of the fractions were ensured as the dependent on the pH, salt and
sugar, temperature, concentration, particle size of the samples in the range of 0.2-40 GHz by
statistical modelling.
Results
While increasing pH value and decreasing particle size at 915 MHz and 2450 MHz, ε' (60.8548.39); (60.25-47.79) and δp (1.41-0.83cm); (0.41-0.32cm) decreased, ε" (28.17-47.76);
(37.81-46.44) increased. In regard to the ion-dependent permittivities, ε' changed in the range
of 66.44-89.9 and 73.28-47.99; δp decreased from 5.28 to 0.63 cm and from 1.33 to 0.33 cm,
ε" increased from 7.99 to 82.69 and from 11.85 to 46.84. When concentration of pomace
increased, ε' (76.79-67.88); (75.7-65.68) and δp (7.93-3.95cm); (1.63-1.19cm) decreased, ε"
(5.64-11.21); (10.2-13.29) increased, respectively.
Conclusion
pH variation is dominant to the particle size distribution of the samples for overall dielectric
properties at two frequencies.
Sucrose is more effective ionic compound on the dielectric properties than D-glucose.
From temperature, concentration, particle size aspects; temperature is more powerful to
change ε', but the concentration of the fractions was found to be more effective on the ε" and
δp for both frequencies.
Keywords: Dielectric constant, loss factor, penetration depth, permittivity, sour cherry,
waste.