scholarly journals Effects of Moisture, Temperature, and Salt Content on the Dielectric Properties of Pecan Kernels During Microwave and Radio Frequency Drying Processes

Foods ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 385 ◽  
Author(s):  
Zhang ◽  
Li ◽  
Cheng ◽  
Wang ◽  
Ding ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Moisture Content ◽  
Radio Frequency ◽  
Salt Content ◽  
Rf Heating ◽  
Dielectric Heating ◽  
Time Histories ◽  
Properties Of Materials ◽  
Content Range ◽  
Temperature Time

Dielectric properties of materials influence the interaction of electromagnetic fields with and are therefore important in designing effective dielectric heating processes. We investigated the dielectric properties (DPs) of pecan kernels between 10 and 3000 MHz using a Novocontrol broadband dielectric spectrometer in a temperature range of 5–65 °C and a moisture content range of 10–30% wet basis (wb) at three salt levels. The dielectric constant (ε′) and loss factor (ε′′) of the pecan kernels decreased significantly with increasing frequency in the radio frequency (RF) band, but gradually in the measured microwave (MW) band. The moisture content and temperature increase greatly contributed to the increase in the ε′ and ε′′ of samples, and ε′′ increased sharply with increasing salt strength. Quadratic polynomial models were established to simulate DPs as functions of temperature and moisture content at four frequencies (27, 40, 915, and 2450 MHz), with R2 > 0.94. The average penetration depth of pecan kernels in the RF band was greater than that in the MW band (238.17 ± 21.78 cm vs. 15.23 ± 7.36 cm; p < 0.01). Based on the measured DP data, the simulated and experimental temperature-time histories of pecan kernels at five moisture contents were compared within the 5 min RF heating period.

scholarly journals Dielektrické vlastnosti zemědělských produktů a některé jejich aplikace

2008 ◽  
Vol 54 (No. 2) ◽  
pp. 104-112 ◽  
Author(s):  
S.O Nelson
Keyword(s):  
Dielectric Properties ◽  
Moisture Content ◽  
Radio Frequency ◽  
Fruits And Vegetables ◽  
Agricultural Products ◽  
Dielectric Heating ◽  
Quality Factors ◽  
Poultry Products ◽  
Microwave Dielectric ◽  
Microwave Dielectric Heating

The use of dielectric properties of agricultural products for sensing moisture in grain and seed and their application in radio-frequency and microwave dielectric heating is discussed briefly. Values for the dielectric properties of a number of products, including grain and seed, fruits and vegetables, and poultry products, are presented graphically to show the dependence of these properties on frequency, moisture content, and temperature. The potential for using the dielectric properties to sense quality factors other than moisture content is also considered.

scholarly journals Electrical Properties of Sunflower Achenes

2014 ◽  
Vol 17 (4) ◽  
pp. 109-113 ◽  
Author(s):  
Ján Novák ◽  
Ivan Vitázek
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Moisture Content ◽  
Electric Field ◽  
Loss Tangent ◽  
Dielectric Heating ◽  
Electrical Measurements ◽  
Engineering Research ◽  
Dielectric Constant And Loss ◽  
Properties Of Materials

Abstract This work contains the results of measuring the electrical properties of sunflower achenes. The interest in electrical properties of biological materials resulted in engineering research in this field. The results of measurements are used for determining the moisture content, the surface level of liquid and grainy materials, for controlling the presence of pests in grain storage, for the quantitative determination of mechanical damage, in the application of dielectric heating, and in many other areas. Electrical measurements of these materials are of fundamental importance in relation to the analysis of quantity of absorbed water and dielectric heating characteristics. It is a well-known fact that electrical properties of materials, namely dielectric constant and conductivity, are affected by the moisture content of material. This fact is important for the design of many commercial moisturetesting instruments for agricultural products. The knowledge of dielectric properties of materials is necessary for the application of dielectric heating. The aim of this work was to measure conductivity, dielectric constant and loss tangent on samples of sunflower achenes, the electrical properties of which had not been sufficiently measured. Measurements were performed under variable moisture content and the frequency of electric field ranging from 1 MHz to 16 MHz, using a Q meter with coaxial probe. It was concluded that conductivity, dielectric constant and loss tangent increased with increasing moisture content, and dielectric constant and loss tangent decreased as the frequency of electric field increased.

scholarly journals Quality of Milled Rice from Large-Scale Dried Paddy Rice by Hot Air Combined with Radio Frequency Heating

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2277
Author(s):  
Karn Chitsuthipakorn ◽  
Sa-nguansak Thanapornpoonpong
Keyword(s):  
Moisture Content ◽  
Radio Frequency ◽  
Block Design ◽  
Specific Energy Consumption ◽  
Brown Rice ◽  
Convective Drying ◽  
Control Treatment ◽  
Rf Heating ◽  
Drying Time ◽  
Hot Air

A scaled-up process for paddy drying was developed using hot air (HA) combined with radio frequency (RF) heating. The study was conducted using hot air (control treatment) arranged in descending order in four temperature levels, namely 80 °C at moisture content of 25–26%, 70 °C at moisture content of 20–25%, 60 °C at moisture content of 17–20%, and 50 °C at moisture content of 13–17%, as well as with hot air combined with radio frequency (HA/RF) at different paddy temperatures (45–60 °C) by adjusting the appropriate RF energy when passing through RF heating chamber, namely HA/RF45, HA/RF50, HA/RF55, and HA/RF60. Each treatment was performed in three replicates and data were statistically analyzed in a randomized complete block design. The quality attributes of paddies affected by the drying process were assessed: fissure percentage, color, milling quality, and sensory evaluation. The drying efficiency showed that the drying time and the specific energy consumption could be decreased by up to 54.44% and 23.17% at HA/RF60 and HA/RF45, respectively. As the RF heating temperature increased, the fissure percentage of brown rice kernels at HA/RF45 and HA was not significantly impacted. Regarding color evaluation, combining RF heating and convective drying at all given conditions could be statistically applied in terms of the b*, WI, and ΔE* value. Considering the milling yield of HA as the baseline, head rice yield was maximized at HA/RF45, while bran yield reached the maximum at HA/RF60. The liking score of cooked rice after it was dried using the HA method was the highest. This study concludes that the HA/RF45 was the most appropriate drying condition, and this may provide preliminary exposure to the industrial drying of paddies.

scholarly journals Electrical Prope Rties of Popcorn Grains

2013 ◽  
Vol 16 (2) ◽  
pp. 43-46
Author(s):  
Ján Novák
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Moisture Content ◽  
Electric Field ◽  
Loss Tangent ◽  
Dielectric Heating ◽  
Electrical Measurements ◽  
Engineering Research ◽  
Dielectric Constant And Loss ◽  
Properties Of Materials

Abstract This work contains the results of measuring the electrical properties of popcorn grains. Interest in electrical properties of biological materials resulted in engineering research in this field. The results of measurements are used for determining the moisture content, the surface level of liquid and grainy materials, for controlling the presence of pests in grain storage, for a quantitative determination of mechanical damage, in applications of dielectric heating, and in many other cases. Electrical measurements on these materials are of fundamental importance in relation to the analysis of quantity of absorbed water and dielectric heating characteristics. It is a well-known fact that electrical properties of materials, namely dielectric constant and conductivity, are affected by the moisture content of material. This fact is important for the design of many commercial moisture-testing instruments for agricultural products. The knowledge of dielectric properties of materials is necessary for the application of dielectric heating. The aim of this work was to perform the measurements of conductivity, dielectric constant and loss tangent on samples of popcorn grains, the electrical properties of which had not been sufficiently measured. Measurements were performed under variable moisture content and the frequency of electric field in the range from 1 MHz to 16 MHz, using a Q meter with a coaxial probe. It was concluded that conductivity, dielectric constant and loss tangent increased with increase of moisture content, and dielectric constant and loss factor decreased as the frequency of electric field increased.

scholarly journals Combined Effect of Temperature and Oil and Salt Contents on the Variation of Dielectric Properties of a Tomato-Based Homogenate

Foods ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3124
Author(s):  
Andres Abea ◽  
Pere Gou ◽  
Maria Dolors Guardia ◽  
Sancho Bañon ◽  
Israel Muñoz
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Olive Oil ◽  
Loss Factor ◽  
Salt Content ◽  
Effect Of Temperature ◽  
Dielectric Heating ◽  
Know How ◽  
Increasing Temperature ◽  
Added Salt

Tomato-based processed foods are a key component of modern diets, usually combined with salt and olive oil in different ratios. For the design of radiofrequency (RF) and microwave (MW) heating processes of tomato-based products, it is of importance to know how the content of both ingredients will affect their dielectric properties. Three concentrations of olive oil and salt were studied in a tomato homogenate in triplicate. The dielectric properties were measured from 10 to 3000 MHz and from 10 to 90 °C. Interaction effects were studied using a general linear model. At RF frequencies, the dielectric constant decreased with increasing temperature in samples without added salt, but this tendency was reversed in samples with added salt. The addition of salt and oil increased the frequency at which this reversion occurred. At MW frequencies, the dielectric constant decreased with increasing temperature, salt, and oil content. The loss factor increased with increasing salt content and temperature, except in samples without added salt at 2450 MHz. Penetration depth decreased with increasing frequency and loss factor. Salt and oil contents have a significant effect on the dielectric properties of tomato homogenates and must be considered for the design of dielectric heating processes.

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