نویسندگان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Information on dielectric properties of food and agriculture materials is needed for developing of electrical technologies in the agricultural and food industries such as radio frequency and microwave heating and non-destructive moisture measurement. In this study, a simple procedure based on two port coaxial transmission/reflection line is presented to measure the dielectric properties of biomaterials and agricultural products at radio frequency (RF) and microwave (MW) frequencies. The transmission line was designed and manufactured by stainless steel. The designed set up can measure the dielectric properties of small values of little objects like insects in different temperatures. The dielectric properties of 'Golden Delicious (GD)', 'Red Delicious (RD)' apples, as fresh fruit and walnut, and pistachio as kernel nuts at initial moisture content were measured. The tests were carried out at five temperature levels between ?? to ??? and four frequencies i.e. ??, ??, ?? and ??? MHz, which are allocated for ISM (Industrial, Scientific and Medical) applications. The electric bender is used to cut fruit flesh into paste and the nut kernel to powder. The initial moisture content of Red Delicious, Golden Delicious apples, pistachio, and walnut samples were ??, ??, ?, and ?% w.b, respectively. The dielectric properties of samples were measured by the two-port coaxial probe transmission line and the vector network analyzer. The results showed that dielectric constant and dielectric loss factor decreased with increasing frequency. The dielectric constant and dielectric loss factor for all tested materials increased with temperature. The dielectric loss factor of fresh fruits and kernel nut increased almost linearly with increasing temperature at radio frequency, but remained nearly constant at ??? MHz microwave frequency. The results showed that dielectric constant and dielectric loss factor of apple with high moisture content were larger than pistachio and walnut with low moisture content. The penetration depth decreased with increasing the frequency and temperature.
کلیدواژهها [English]
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