A comparison between the open-ended coaxial probe method and the parallel plate method for measuring the dielectric properties of low-moisture foods

Lau, Soon Kiat; Dag, Damla; Ozturk, Samet; Kong, Fanbin; Subbiah, Jeyamkondan

doi:10.1016/j.lwt.2020.109719

Cited by 17 publications

(10 citation statements)

References 46 publications

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“…Then, the vector network analyzer and the coaxial probe with an open-end were calibrated. The network analyzer was calibrated using deionized water, air, and short circuit, and the sensitivity of the open coaxial probe was tested as suggested by Lau et al (2020).…”

Section: Determination Of Dielectric Propertiesmentioning

confidence: 99%

Dielectric properties of edible fungi powder related to radio-frequency and microwave drying

Han

Lagnika

et al. 2021

Food Prod Process and Nutr

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Edible fungi are rich in nutrition, but they are susceptible to spoilage, and often prolonged by drying. RF and microwave energy drying have the advantages of short drying time, high energy efficiency and good process control. However, to develop an effective dielectric drying method, it is important to understand dielectric properties, the major factor characterizing the interaction between the electromagnetic energy and the food. At present, there is a lack of research on dielectric properties of edible fungi. In this study, a vector network analyzer and an open-ended coaxial-line probe were employed to measure the dielectric parameters. The dielectric parameters were observed at different temperatures (25–85 °C) for edible fungi powder with moisture content ranging from 5 to 30% wet basis over a frequency range of 1–3000 MHz. The relationship between the dielectric properties and frequency, temperature, and moisture content were obtained via regression analysis. Further, the dielectric penetration depth was calculated, and the effects of frequency, moisture content, and temperature on the penetration depth were also analyzed. The results showed that the dielectric properties of edible fungi powder increased with an increase in moisture content and temperature, while they decreased with increasing frequency. At high moisture content and temperature, the increase in dielectric properties was slightly larger than that at low moisture content and temperature. The dielectric properties changed more evidently at lower radio frequencies than at higher radio frequencies. The penetration depth decreased with an increase in temperature, moisture content, and frequency. It can be concluded that a large penetration depth at radio frequencies below 100 MHz could be used to dry edible fungi on a large scale, whereas microwave energy could be employed for drying edible fungi on a small scale.

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Section: Determination Of Dielectric Propertiesmentioning

confidence: 99%

Dielectric properties of edible fungi powder related to radio-frequency and microwave drying

Han

Lagnika

et al. 2021

Food Prod Process and Nutr

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“…The complex permittivity (ε * ) consists of the real and imaginary part [1,3,10]:…”

Section: Methodsmentioning

confidence: 99%

“…It is also widely used for determination of the pollution of oils, fuels and lubricants in power engineering [6,7] and for measurements of dielectric properties in bio-applications [1,5,8]. Measurements of the dielectric characteristics are of particular importance in monitoring and controlling of liquids in situations where quality is a critical factor [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…Such a method is simpler, but compared to the method with a resonator, its accuracy is lower. The method with an open coaxial probe [10,26,27] is used for dielectric measurements of agricultural products and can be used for testing of liquid, soft and solid materials. The drawback of the method is in its lower accuracy below 200 MHz and, in general, for materials which have low dielectric constants and loss factors.…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity and Accuracy of Dielectric Measurements of Liquids Significantly Improved by Coupled Capacitive-Dependent Quartz Crystals

Matko

Milanovič

2021

Sensors

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A method to measure complex permittivity of liquids by using a capacitive-dependent quartz crystal and two quartz oscillators for temperature compensation in the frequency range of 4–10 MHz is described. Complex permittivity can be detected with high precision and sensitivity through a small change of capacitance and conductance, because a change in reactance in series with the quartz crystal impacts its resonant oscillation frequency. The temperature compensation in the range below 0.1 ppm is achieved by using two quartz oscillators that are made of elements of the same quality and have a temperature–frequency pair of quartz crystals. With the help of a reference oscillator, measurements of frequency are more accurate, because the frequency difference is in the kHz region, which also enables further processing of the signal by a microcontroller. With a proper calibration, the accuracy of this highly sensitive quartz crystal method is ±0.05%, which is an order of magnitude lower than that for a capacitance method without quartz crystals. The improved accuracy is of significant importance in the field of power engineering to monitor coolants and lubricants, oils, liquid fuels and other liquids, the dielectric properties of which are crucial for proper operation of devices.

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“…Dielectric properties measurement using open‐ended coaxial probe is becoming more convenient, easy to use, and quick due to its commercial availability; also it has a large bandwidth, and requires little sample preparation (Hussein et al, 2019; Regier & Schubert, 2005). Furthermore, the accuracy of the measured dielectric properties is adequate for most dielectric heating research (Lau, Dag, Ozturk, Kong, & Subbiah, 2020; Tang & Lau, 2002).…”

Section: Introductionmentioning

confidence: 99%

Osmotic dehydration under low agitation laminar flow condition: Effect on dielectric properties of broccoli stalk slices at 2.45 GHz

Salim

Gariépy

Raghavan

2021

J Food Process Engineering

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The variation in dielectric constant, ε′ and the loss factor, ε″ of broccoli stalk slices after osmotic dehydration process conducted under continuous solution circulation with low agitation laminar flow condition was studied using open‐ended coaxial probe technique at 2.45 GHz. The results showed that both ε′ and ε″ were significantly influenced by all the osmotic dehydration operating variables. The relationship of osmotic dehydration operating variables on the dielectric properties of the broccoli stalk slices could be established by second‐order polynomial model, with the coefficient of determination higher than .9. Compared to fresh sample, the ε′ decreases and ε″ increases when broccoli stalk is subjected to the osmotic dehydration pretreatment under its optimum conditions of mass transfer exchange process. Higher dissipation factor with shorter penetration depth was obtained after osmotic pretreatment, which could facilitate absorption of energy during microwave drying of broccoli stalk slices.Practical ApplicationsDielectric properties are key factors to understand the interaction of microwaves with food materials. In recent years, there has been an increasing interest in osmotic dehydration used as pretreatment prior to microwave drying to achieve faster drying time and improves the final product quality. As osmotic dehydration process will cause a change in the dielectric properties of the food material and its ability to absorb microwaves energy, this work investigated the effects of osmotic dehydration on the dielectric properties of broccoli stalk slices at 2.45 GHz. The osmo‐pretreated sample improved the dielectric properties which result in rapid heating and therefore lead to fast drying process. The information provided in this study is helpful in the development of dried broccoli stalk slices using microwave drying.

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A comparison between the open-ended coaxial probe method and the parallel plate method for measuring the dielectric properties of low-moisture foods

Cited by 17 publications

References 46 publications

Dielectric properties of edible fungi powder related to radio-frequency and microwave drying

Dielectric properties of edible fungi powder related to radio-frequency and microwave drying

Sensitivity and Accuracy of Dielectric Measurements of Liquids Significantly Improved by Coupled Capacitive-Dependent Quartz Crystals

Osmotic dehydration under low agitation laminar flow condition: Effect on dielectric properties of broccoli stalk slices at 2.45 GHz

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