Frequency and moisture dependence of the dielectric properties of hard red winter wheat

Nelson, Stuart O.; Stetson, L. E.

doi:10.1016/0021-8634(76)90073-1

Cited by 112 publications

(79 citation statements)

References 13 publications

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“…Below 12% moisture content, the dielectric loss suggest a non-linear response with increasing moisture content, as previously observed for similar agri-food materials (Serdyuk 2008), attributable to the dominance of water bound to the malt structure which has a low extent of polarizability. Similar trends are seen in the dielectric properties of hard red winter wheat as measured by Nelson (1976). The lower dielectric losses at 2450 MHz in the bound water region below 12% moisture indicate that this is a critical moisture level (CML) in the industrial drying of malt.…”

Section: Bulk Microwave Measurementssupporting

confidence: 71%

Electromagnetic Heating for Industrial Kilning of Malt: a Feasibility Study

Ferrari

Katrib

Zerva

et al. 2016

Food Bioprocess Technol

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Industrial malting operations use ~800kWh/t of energy to produce the heat required to kiln malt. Electromagnetic heating technologies are suggested as a way to potentially improve the energy efficiency of the kilning processing. In this work, the potential for using electromagnetic heating to dry malt to commercially acceptable moisture levels, whilst preserving the activity of enzymes critical for downstream brewing processes is investigated. The 2450 MHz bulk dielectric properties of malt at moisture contents consistent with those occurring at different points in the kilning process are evaluated; 12% is shown to be a critical moisture level below which drying becomes more energy intensive.Calculated penetration depths of electromagnetic energy in malt at radio frequency are 100 fold higher than at microwave frequencies, showing a significant advantage for commercial scale batch processing. The moisture contents and alpha and beta amylase activity of malt subjected to RF heating at different temperatures, treatment times and RF energy inputs in the intermediate and bound water drying regions were determined. It is shown for the first time that whilst significantly reduced process times are attainable, significant energy efficiency improvements compared to conventional kilning can only be achieved at higher product temperatures and thus at the expense of enzyme survival.It is suggested that RF heating may be feasible where higher bulk temperatures are not critical for downstream use of the material or when used in hybrid systems. 1 IntroductionBy 2030, it is predicted that global population growth will increase food production demands by 50% and energy demands by 45% (Beddington 2009). Consequently, food and energy security is high on the agenda of many governments (Tassou et al. 2014). The UK Government's Climate Change Agreements (CCA) scheme has been implemented to provide discounts on the Climate Change Levy (CCL) for energy intensive industries that meet targets for reduced energy use and CO2 emissions.The UK malting sector has targeted a 4.7% improvement in energy efficiency by 2020 (DEFRA 2013). This is in addition to a 12% target saving from 1999 to 2010. UK maltsters currently consume some 1375 GWh of secondary energy a year in the production of around 1.5 million tonnes of malt; at least 78% of this energy is used to provide heat

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Section: Bulk Microwave Measurementssupporting

confidence: 71%

Electromagnetic Heating for Industrial Kilning of Malt: a Feasibility Study

Ferrari

Katrib

Zerva

et al. 2016

Food Bioprocess Technol

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“…The basic aim of the work is to determine the dependence of the dielectric permittivity of bound water on its moisture content in bulk grain. For this, we use the results of dielectric measurements for bulk grain of winter wheat at various frequencies, presented in [15]. There is a great amount of later experimental data on dielectric properties of bulk grain in modern literature.…”

Section: Introductionmentioning

confidence: 99%

“…There is a great amount of later experimental data on dielectric properties of bulk grain in modern literature. However, the authors of [15], besides the results on measurement of dielectric permittivity, presented also bona fide the data on measurement of bulk density and kernel density for grain samples under study, which is necessary for electromagnetic simulation.…”

Section: Introductionmentioning

confidence: 99%

Dielectric Study of Bound Water in Grain at Radio and Microwave Frequencies

Serdyuk

2008

PIER

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Abstract-A phenomenological theoretical model of grain dielectric properties is presented for radio and microwave frequencies. On the bases of this model, an inverse problem is solved to determine the dielectric permittivity of bound water inside kernels of winter wheat using results of complex permittivity measurements for bulk grain carried out by other authors. The character of the water complex permittivity dependence on frequency and kernel moisture content is studied. For this, the permittivity was considered as a sum of five different functions, depending on moisture content explicitly, and with coefficients being subject to determination. The frequency dependence of these coefficients was analyzed, and the regions typical for the ionic conductivity and for the dipole-orientational polarization mechanism were detected. For this polarization mechanism, the relaxation frequencies are differ from those of free water. It was concluded that water microparticles inside kernels are formed not by pure water, but by aqueous solution of four different substances coming from the kernel solid phase. It is shown that bound water, for the most part, is in a state that is intermediate between that of free water and that of molecules in the monomolecular water layer on the solid phase boundary.

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“…Quanto ao efeito da composição química das sementes sobre suas propriedades dielétricas, os estudos continuam incipientes e limitados. Nelson e Stetson (1976) não observaram efeito significativo dos teores de proteína, óleo e cinzas sobre as propriedades dielétricas de sementes de trigo de nove variedades diferentes.…”

Section: Resultsunclassified

Determinação do teor de água de sementes de café empregando o método da capacitância em radiofreqüências

Berbet

Molina

Carlesso

et al. 2007

Rev. bras. sementes

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, VINICIUS OLIVEIRA CARLESSO 4 , MÁRCIA TEREZINHA RAMOS OLIVEIRA 5 RESUMO -O desenvolvimento de modelos matemáticos que correlacionem a permissividade elétrica relativa ε' e o fator de perda dielétrica ε" à quantidade de água presente em amostras de sementes é um passo fundamental no desenvolvimento de medidores em linha do teor de água que possam ser empregados no controle automático de processos como colheita, secagem e aeração. Esse trabalho consistiu na avaliação de três modelos dielétricos para determinação do teor de água de sementes de café, sem a influência do fluxo de massa. Foram utilizadas amostras das variedades Catuaí Amarelo, Catuaí Vermelho e Mundo Novo, com teores de água entre 11 e 23% b.u. e massa específica aparente no intervalo 326 kg m -3 < ρ < 455 kg m -3. Dos modelos obtidos, apenas aquele que utiliza a medição simultânea de ε' e ε", a 0,5 e 5,0 MHz, permite estimar o teor de água de sementes de café com o grau de acurácia desejado. Os erros padrão de calibração e predição foram de 1,3 e 1,2 pontos percentuais, respectivamente.Termos para indexação: Coffea arabica, umidade, propriedades dielétricas, instrumentação. MOISTURE DETERMINATION IN COFFEE SEEDS BY THE CAPACITANCE METHOD AT RADIOFREQUENCIESABSTRACT -The development of mathematical models capable of relating the relative permittivity ε' and the loss factor ε" of seeds to their moisture content is a fundamental step towards designing seed moisture meters for on-line operations in automatic control processes such as seed harvest, drying and aeration. The object of this research is the assessment of three dielectric models that would allow the density-independent determination of the moisture content of moving seeds of parchment coffee. Seed samples of varieties Catuaí Amarelo, Catuaí Vermelho and Mundo Novo with moisture contents in the range from 11 to 23% w.b., and bulk density ranging from 326 to 455 kg.m -3 have been used. In terms of instrumentation accuracy the best bulk-density dielectric model for coffee seeds moisture content estimation was the one which employed both ε' and ε" measured at 0.5 and 5.0 MHz as indicators of the amount of water present in the seed samples. The standard errors of calibration and prediction were 1.3 and 1.2 percentage points moisture, respectively

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Frequency and moisture dependence of the dielectric properties of hard red winter wheat

Cited by 112 publications

References 13 publications

Electromagnetic Heating for Industrial Kilning of Malt: a Feasibility Study

Electromagnetic Heating for Industrial Kilning of Malt: a Feasibility Study

Dielectric Study of Bound Water in Grain at Radio and Microwave Frequencies

Determinação do teor de água de sementes de café empregando o método da capacitância em radiofreqüências

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