SELECTED ELECTRIC PROPERTIES OF PERGA

Transcription

1 SELECTED ELECTRIC PROPERTIES OF PERGA TOMAS REGRUT 1, JAN NOVAK 1, ZUZANA HLAVACOVA 1, JAN BRINDZA 2, VALERYI BROVARSKYI 3, SERHII VELYCHKO 3 1 Depatment of Physics 2 Depatment of Genetics and Plant Beeding Slovak Univesity of Agicultue in Nita T. Andeja Hlinku 2, Nita SLOVAKIA 3 Depatment of Beekeeping National Univesity of Life and Envionmental Sciences of Ukaine Heoiv Oboony St. 15, Kiev UKRAINE tegut@gmail.com Abstact: Measuement of electical popeties is one of the most impotant opeations in the collection, stoage and pocessing of the agicultual poduction. The physical popeties of biological mateials affect measuement accuacy. Bee bead also called "Pega" ae femented bees pollen in the comb, which stoe bees as potein supply. Bee bead is consideed the most pefect of all natual foods used by the Geeks as ambosia. It includes many vitamins and tace elements. We measued seveal electical popeties, such as capacitance, esistance, impedance and loss facto. Fom measued and calculated values ae constucted gaphical dependencies of electical quantities on fequency and moistue content. We found out that all measued electical popeties deceased with fequency, incease of the moistue content caused the gowths of electical popeties. Key Wods: pega, electical popeties, fequency, moistue content INTRODUCTION Bee bead also called "Pega" ae femented bees pollen in the comb, which stoe bees as potein supply. The bee bead is havested by hand fom the honeycomb and thus is not only the most valuable, but also the most expensive bee poducts (McIntye and Snyde 1978). Bee bead is consideed the most pefect of all natual foods used by the Geeks as ambosia. It includes many vitamins (A, B1, B2, B6, B12, C, D, E, P, PP) and tace elements (potassium, magnesium, calcium, coppe, ion, silicon, sulphu, chloine, manganese) (McIntye and Snyde 1978). In the pega thee is eveything that is equied fo the nomal gowth and existence of a live oganism. Good esults ae noted by specialists at teatment of patients with many diseases (Geogiev et al. 24). The dielectic popeties of foods and biological poducts have become valuable paametes in food engineeing and technology. The investigation of mateial and moistue measuement using electomagnetic waves in wide spectum seve fo quality contol and impovement in many banches like industy, foest and wood woking industy, civil engineeing, agicultue, commece and also foods e. g. fo quality evaluation of meat, fuits, coffee etc. (Hlaváčová 23, Venkatesh 25). The study of electical popeties is impotant fo pedicting the behaviou of a mateial in electic field o fo knowing how the pesence of mateial can influence the field o an associated electical cicuit. Electical measuements on these mateials ae of fundamental impotance in elation to the analysis of quantity of absobed wate and dielectic heating chaacteistics. Dielectic popeties of mateials epesent an impotant pat of electical popeties. The eseach of electical popeties is finding utilisation in a lot of technical applications. Results of measuements ae used fo detemining the moistue content, the suface level of liquid and gainy mateials, fo contolling the pesence of pests in gain stoage, fo the quantitative detemination of mechanical damage, and in many othe cases (Hlaváčová 23, Kuang and Nelson 1998). It was discoveed that electic popeties of these mateials ae vey affected by moistue content of the mateial. Small quantities of adsobed wate can cause lage changes in electical popeties of hydoscopic mateials. An extensive eview of the liteatue on 628 P age

2 dielectic popeties of agicultual mateials was published by Nelson and Tabelsi (28) that includes a numbe of potential applications in which the dielectic popeties of such poducts ae of inteest. Evey mateial influences the electic field to which it is subjected. The elation between paametes of electomagnetic field and popeties of mateial medium is descibed with pemittivity ε and pemeability µ of this medium. Both paametes descibe electomagnetic popeties of matte. A wok of Babosa Canovas et al. (26) deals with the measuement of these paametes. Pemittivity is complex quantity ε = ε j ε (1) The eal pat of complex pemittivityε is the pemittivity of dielectic ε. The coefficient of imaginay pat ε chaacteises losses in dielectic. Dielectic popeties of mateials ae geneally fomulated by elative complex pemittivity ε * ε ε ε * = = j = ε jε = ε ( 1 tgδ ) (2) ε ε ε whee o ε ε σ tg δ = = = (3) ε ε ωε is loss tangent of loss angle δ, it is the angle completing to 2 π phase diffeence between voltage and cuent flowing though the dielectic. ε o is vacuum pemittivity ( F/m), ε o ε is elative pemitivity o dielectic constant, j is imaginay unit, σ is conductivity of mateial, ω is angula fequency. To measue the dielectic popeties of samples, a esonant method has been used. This method fo measuing the dielectic popeties of seeds and liquids in a fequency ange fom 1 khz to 3 khz was developed by Nelson et al. (27). MATERIAL AND METHODS Pega Bee bead also called "Pega" ae femented bees pollen in the comb, which stoe bees as potein supply. Pega samples of diffeent plant species wee collected by beekeepes fom selected egions of Ukaine (Poltava and Dnepopetovsk) accoding to a new patented technology developed by the eseach team of the Depatment of Apicultue at the National Univesity of Life and Envionmental Sciences of Ukaine, with offices in Kiev. All samples wee polyfloal Pega. Electical popeties measuement All measuements wee caied out unde an ai tempeatue of 2 C and of 6% elative humidity. Bulk density was detemined by the mass of constant sample volume. We used two methods of measuement by LCR mete and Q mete. Low fequency electical popeties of pega wee measued by an instument GoodWill Instek LCR mete 821 at diffeent fequencies using fou-electode (teta pola) system. The sample was placed in the senso with paametes: diamete of electode 37.8 mm, electodes spacing 49.2 mm, mass of empty senso g. We measued capacitance, esistance, impedance and loss facto. Each popety was measued in the fequency ange fom.1 khz to 2 khz, at all fequencies thee times. Aveage value has been computed fom these ones and standad deviation was calculated. The measued values wee loaded by PC. The capacitance of the testing capacito was measued by the Q mete TESLA MB 56. By measuing the pemittivity ε of testing capacito, the eal capacito can be consideed as a lossless capacito connected with active esistance in a paallel o seial configuation. The substance of measuement is to detemine the magnitude of capacitance and esistance of paallel o seial configuation of dielectic at a specific fequency. The Q mete was connected with the testing coaxial 629 P age

3 capacito, which was used as a sample holde. The measuement was pefomed in a fequency ange fom 1 MHz to 16 MHz. Dielectic constant ε was calculated accoding following elations C C x ε = (4) C C = C 1 C 2 (5) whee C capacitance of testing capacito with a sample, F C o capacitance of empty testing capacito fee of inteconnecto capacitance, F C x capacitance of inteconnecto, F C 1 capacitance of tuning capacito by esonance and by non-connection of testingcapacito, F C 2 capacitance of tuning capacito by esonance and by connection of testing capacito, F The esistance R of testing capacito was measued using multimete MASTER M83BUZ. Conductivity of the sample σ was detemined accoding following elation 1 ln 2 σ = (6) 2π l R whee 1 adius of capacito oute electode,.33 m 2 adius of inne electode,.8 m l length of capacito,.6 m Moistue content measuement Moistue content wet basis was detemined by gavimetic method. The samples wee weighed by Satoius Basic electonic analytical and pecision balance (Satoius AG) on the beginning and afte dying andeaching constant mass. Moistue content was calculated accoding the following elation m1 m2 w = 1 % (7) m1 whee m 1 initial mass of sample m 2 mass of dy sample Diffeent moistue content w of samples was achieved by natual dying. RESULTS AND DISCUSSION Measuement by RLC mete Fom measued values at initial moistue content ae constucted gaphical dependencies of electical quantities on fequency. Fo illustation, the esistance and impedance vesus fequency cuves ae shown on Figue 1. The esistance and impedance of pega sample deceases in this fequency ange. The egession equation fo esistance and impedance has the shape of deceasing powe function R = R whee R esistance, kω R = kω efeence esistance, f fequency, f = 1 khz, f f k o (8) 63 P age

4 k = constant. Figue 1 The esistance ( ) and impedance ( ) vesus fequency cuves Resistance, impedance (k ) Fequency (khz) The simila equation can be wite also fo impedance. The coefficient of detemination has high value R 2 =.989 fo esistance and.9427 fo impedance. The change of esistance and impedance at low fequency is significant, compaed to the highe fequencies. The impedance has a slightly highe values as esistance, which is caused by the capacitance of pega. Also the capacitance deceases with fequency accoding to powe function. Only loos facto inceased in this fequency ange. Measuement by Q mete The effect of moistue content on conductivity and dielectic constant ae shown in Figue 2 and 3. Figue 2 Effect of moistue content w on the conductivity σ of pega samples 5E-6 Conductivity ( S/m) 4E-6 3E-6 2E-6 1E-6 E Moistue content ( % ) This inceasing dependency can be also modelled by a powe function k σ = σ w (9) whee σ = S/m efeence conductivity k = constant 631 P age

5 Regession coefficient has also high value R 2 = Figue 3 Moistue content w dependences of dielectic constant ε fo pega samples measued at diffeent fequency f 6 Dielectic constant MHz 6 MHz 11 MHz 16 MHz Moistue content in ( % ) We used also powe function fo modelling these dependencies k ε = ε w (1) whee ε efeence dielectic constant k constant Coefficients of egession equation (1) and coefficient of detemination ae displayed in Table 1. Table 1 Coefficients of egession equation (1) and coefficient of detemination Fequency (MHz) ε k R Also in case of equation (1), it can be see that the coefficient of detemination has high value. Values of dielectic constant incease when the moistue content of samples inceases. This effect is the consequence of a vey high magnitude of dielectic constant of wate in compaison with othe components of pega (Nelson and Tabelsi 28). CONCLUSION The measuements indicate that pega must be included in the most complex objects. It is oganic heteogeneous multi component dielectics. The factos having the highest effect on these effects ae also specified. We found out that the esistance and impedance decease with fequency. The change of esistance and impedance at low fequency is significant, compaed to the highe fequencies. The impedance has a slightly highe values as esistance, which is caused by the capacitance of pega. Also the capacitance deceases with fequency accoding to powe function. Only loos facto inceased in this fequency ange. It was detemined that the dielectic constant of pega inceases when the moistue content of pega inceases. The minimal decease is at highe fequencies. These elationships ae caused by the dipole moment of wate molecules and may be the oientation of chaged goups of macomolecules. In this case, an oientation polaisation occus in electic field. This type of polaisation is highly dependent on fequency. Dipole macomolecules ae not able to follow changes in the polaity 632 P age

6 of electic field. Conductivity values incease when the moistue content of samples inceases. This effect is caused by impovement of conditions fo an electolytic tanspot of chages by dissociated ions in damp medium. ACKNOWLEDGEMENTS This wok was suppoted by eseach poject VEGA 1/854/14 of Ministy of Education, Science, Reseach, and Spot of the Slovakia and was co funded by the Euopean Community unde the poject No : Building the Reseach Cente AgoBioTech. REFERENCES Babosa Canovas, G.V., Juliano, P., Peleg, M. 26. Engineeing Popeties of Foods. Food Engineeing. In Encyclopaedia of Life Suppot Systems. (Ed. V.G. Babosa Canovas). Developed unde Auspices of the UNESCO, EOLSS Publishes. Oxfod, UK. Geogiev, D.B., Goudev, A.G., Manassiev, N. 24. Effects of an Hebal Medication Containing Bee Poducts on Menopausal Symptoms and Cadiovascula Risk Makes: Results of a Pilot Open uncontolled Tial. MedGenMed [online], 4(46): Available at: [ ]. Hlaváčová, Z. 23. Low Fequency Electic Popeties Utilization in Agicultue and Food Teatment. Reseach in Agicultual Engineeing, 49(4): Kuang, W., Nelson, S.O Low-fequency Dielectic Popeties of Biological Tissues: A Review with Some New Insights. Tansaction of the ASAE, 41(1): McIntye, P., Snyde, A.W Light Popagation in Twisted Anisotopic Media: Application to Photoeceptos. Jounal of the Optical Society of Ameica, 68(2): Nelson, S.O., Guo, W., Tabelsi, S., Kays, S.J. 27. Dielectic Spectoscopy of Watemelons fo Sensing Quality. Measuement Science and Technology, 18(7): Nelson,S.O., Tabelsi, S. 28. Dielectic Spectoscopy Measuementson Fuit, Meat, and Gain. Tansactions of the ASABE, 51(5): Venkatesh, M.S., Raghavan, G.S.V. 25. An Oveview of Dielectic Popeties Measuing Techniques. Canadian Biosystems Engineeing, 47(7): P age