Temperature and moisture dependent dielectric properties of legume flour associated with dielectric heating

Guo, Wenchuan; Wang, Shaojin; Tiwari, Garima; Johnson, Judy; Tang, Juming

doi:10.1016/j.lwt.2009.07.008

Cited by 139 publications

(71 citation statements)

References 40 publications

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“…The trend of decreasing dielectric constant with the increasing of frequency was found to be similar with other biomass tested previously such as rubber wood [17], softwood included Black spruce, Balsam fir and Tamarak [19], empty fruit bunch of oil palm [14], oil palm shell, oil palm fibre, biochar from oil palm shell [13], green pea flour, lentil flour and soybean flour [29].…”

Section: A Effect Of Frequencysupporting

confidence: 80%

Dielectric Properties of Oil Palm Trunk Core

Jie¹,

Abdullah²,

Yusof³

et al. 2015

JOCET

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Abstract-Recent development in microwave-assisted processing of biomass materials has significantly created a need for fundamental study to understand the dielectric properties of these biomass feedstock, which could give further insight about interaction between microwave energy and biomass. In the present study, dielectric properties of oil palm trunk (OPT) core were investigated using an open-ended coaxial probe method. The dielectric properties of OPT core were determined as a function of controlling factors such as microwave frequency, biomass moisture content and fibre directions (radial, tangential and cross section). The results showed that dielectric constant of OPT core was decreased with the increasing of frequency. For dielectric loss and loss tangent, a similar trend was observed but only at low frequency (<1.8 GHz). The dielectric constant and loss of OPT core were positively correlated with its moisture content for all fibre directions. In terms of magnitude of dielectric constant and loss, radial direction showed the highest value compared to cross section and tangential which suggests radial direction has the optimum electromagnetic energy absorption and conversion.Index Terms-Oil palm trunk core, dielectric constant, dielectric loss, loss tangent. I. INTRODUCTIONAs main exporter of oil palm, Malaysia has a large area of oil palm plantation. Until December 2012, there were 5.08 million ha area of oil palm plantation covering 15% of the total land area in Malaysia [1]. Oil palm tree has short productivity life span about 25 years. During replanting, it is estimated that around 74 t/ha dry oil palm trunk (OPT) logs are produced giving availability of around 13.6 million OPT logs/year for every 100,000 hectares plantations [2]. The abundant OPT logs are mostly utilized in saw-wood, lumber, plywood, flooring and furniture manufacturing [3], [4]. In the manufacturing of plywood, only the outer part of OPT logs was peeled to be further processed into plywood while the core part comprised only soft parenchyma tissue was left out as waste [5]. The core waste could be converted into cattle feed or further processed into biofuel.For waste conversion of biomass into biofuel and materials, microwave-assisted processes such as microwavepyrolysis and microwave-drying are increasingly applied [2], [6]- [8]. Unlike conventional heat source, microwave energy has several advantageous including volumetric heating allowing bulky and high moisture biomass to be processed, minimize secondary reaction to optimize product yield also permits rapid heating therefore cost and time-saving [6] [11]. The mechanism of microwave energy on biomass involves the transport of the electrical charges by the ions present in the biomass cell wall and cellulose. Once the microwave is encountered the biomass, randomly oriented dipoles in dielectric material align themselves in a direction opposite to applied external electric field. The molecules absorb the energy and store as potential energy. By the mechanism of ionic conduction and d...

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Section: A Effect Of Frequencysupporting

confidence: 80%

Dielectric Properties of Oil Palm Trunk Core

Jie¹,

Abdullah²,

Yusof³

et al. 2015

JOCET

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“…3). The same trends were previously observed for soybeans [13] and soybean flour [15]. In addition, the data in the chart (Fig.…”

Section: B Temperature Datasupporting

confidence: 87%

Analysis of capacitive measurements at low frequencies for moisture content determination in soybeans

Bessa

Ribeiro

Bonfim

et al. 2013

BJIC

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“…The loss factor dependence on gluten efficiency is described by an linear trend shown in the No description of the use of electric methods for determining admixtures of oat meal to wheat flour was found in the available specialist literature. Research on the electric and dielectric features of flour applies only to its conductivity or studies are conducted at very high frequencies, above 10MHz (Guo et al, 2008(Guo et al, , 2010, hence the available literature does not contain data that would permit a discussion of the results obtained during this study. …”

Section: Resultsmentioning

confidence: 99%

“…Studies on determining dielectric and electric properties of flour obtained from various seeds have been conducted around the world for a long time (Guo et al, 2008(Guo et al, , 2010Nelson, 2008). Electrical methods are also used by researchers to analyze the quality of bread (Liu et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Dielectric properties of wheat flour mixed with oat meal

Łuczycka

Czubaszek

Fujarczuk

et al. 2013

International Agrophysics

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A b s t r a c t. Possibilities of using electric methods for determining admixtures of oat meal to wheat flour, type 650 are presented. In wheat flour, oat meal and mixtures containing 10, 20 and 30% of the oat meal, moisture, protein, starch and ash content, sedimentation value, yield and softening of wet gluten were determined. In samples containing 0, 5, 10, 15, 20, 25, 30 and 100% of oat meal, the dielectric loss factor and conductivity were determined using an impedance analyzer for electromagnetic field frequency ranging from 0.1-20 kHz. It was found that the dielectric loss factor varied for tested material. The best distinguishing between tested mixtures was obtained at the measuring electromagnetic field frequency of 20 kHz. The loss factor was significantly correlated with the yield of wet gluten and the sedimentation value, parameters indicating the amount and quality of gluten proteins in flour.K e y w o r d s: wheat flour, oat middlings, electrical properties, dielectric loss factor INTRODUCTIONThe human diet is based on cereal products, in which bakery products have the largest share. The increasing awareness of producers and consumers resulted in an increase in the range of bakery products with additives improving their value. Such additives may include oat products, as oat protein is characterized by its high biological value (Peterson et al., 2005). Exogenous amino acids form about 40% of it, while in wheat and rye protein their content reaches only 30% (Ralecewicz and Knapowski, 2006). In oat grain there are a lot of lipids with a significant content of unsaturated fatty acids (Czubaszek, 2008;Hampshire, 2004;Peterson et al., 2005). Furthermore, in those lipids also present are tocopherols and tocotrienols, compounds with anti-cancer activity, additionally preventing cardiovascular diseases. A component, which had the largest contribution to the increase in interest in oats, is dietary fibre containing about 50% of soluble fraction and b-glucans (Hampshire, 2004). Oats bran is particularly rich in fibre, with a 24% content of that component (Zarzycki and Rzedziecki, 2009). Compounds present in oat fibre absorb substances harmful to health ie heavy metals, residues of plant protection agents from food and prevent them being absorbed by the body. They also bind cholesterol in the human digestive system thus reducing its assimilation and reducing its levels in blood. This is of enormous significance for prophylactics of diseases such as arteriosclerosis or ischaemic heart disease (Peterson et al., 2005;Weawer and Schneeman, 2005). It was demonstrated that bakery products with oat additives might have good physical and organoleptic properties (Czubaszek, 2008;Flander et al., 2004;Meltzer, 2005; SalmenkallioMarttila et al., 2004).So far, for determining the presence of admixtures in flour the microscopic evaluation of starch granules was used, as they are characterized by different sizes, shapes or surface structures, depending on their origin. Studies on determining dielectric and electric propert...

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Temperature and moisture dependent dielectric properties of legume flour associated with dielectric heating

Cited by 139 publications

References 40 publications

Dielectric Properties of Oil Palm Trunk Core

Dielectric Properties of Oil Palm Trunk Core

Analysis of capacitive measurements at low frequencies for moisture content determination in soybeans

Dielectric properties of wheat flour mixed with oat meal

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