Chapter-V Comparative Dielectric Study of Basmati Rice (Oryza sativa L.) and Urad (Vigna Mungo L.) of Two Varieties of Each

Transcription

1 Chapter-V Comparative Dielectric Study of Basmati Rice (Oryza sativa L.) and Urad (Vigna Mungo L.) of Two Varieties of Each 5.1 Introduction The dielectric properties of seeds and grains and their dependence on moisture content of them have been of great importance because of their application in the measurement of moisture content (1). The moisture content measurement of the grains is important from the point of view of preservation of stored grains and their protection from insects. This preservation and protection can be achieved by dielectric heating ( 2).Therefore a lot of research work has been done on cereals and grains and many factors that affect, the electrical parameters i.e. dielectric constant, dielectric loss and conductivity have been evaluated from the application point of view. Various researchers have done a lot of work in exploring the various properties of food and edible items to ensure their quality like non distractive test of internal fruit quality (3), improvement of germination of seed (4), dielectric cleaning and separation of seeds by seed separator (5) and improvement of nutritional qualities (6).The dielectric properties of seeds are also helpful in studying the viability test (7), metabolic mechanism of seed (8), hydration mechanism in seed, as well as in the designing of equipments for sensing and monitoring of moisture using electrical methods (9). The electrical parameters for many agricultural materials are influenced by ionic conductivity (10) and water retention of cell (11) but with the development of practical application of microwave energy, need of data on dielectric properties of seeds have gained much importance. There are many brands of rice in the market. Thus, this gives raise to the need to determine and characterize the quality of rice properly to ensure that all types of rice can be priced accordingly. Rice grain quality evaluation procedures reported by Dela Cruz, N., et al., (12). In another study, Histochemical and biochemical analysis of major aroma compound (2- acetyl- 1- pyuroline) in basmati and other scented rice (Oryza Sativa L.) reprted by You, K. Y., et al., (13).Recently Ahmed, J., et al., design a cylindrical slot antennas for monitoring the quality of milled rice (14). Dielectric properties of Indian basmati rice flour slurry reported by Ahmed, J., et al., (15). Page 72

2 Therefore present investigations have been undertaken as a comparative study of electrical properties of two variety of basmati rice and two variety of Urad at different moisture levels i.e. the dielectric constant ( ), dielectric loss ( ) and a.c. conductivity ( σ ω ε 0 ε", where o is the permittivity of free space and is angular frequency) has been measured to identify the viable and non-viable grains and to analyze their dependence on moisture level for basmati rice and urad. The measurements have been done in the temperature range of 30 0 C to 51 0 C and with the varying frequency from 5 khz to 10 MHz. The present study was conducted using two varieties of basmati rice and two varieties of urad with a view to evaluate the dielectric properties. 5.2 Material and Methods Basmati Rice (Oryza sativa L.) Classification of Rice 1 Hindi Name Chawal 2 English Name Rice 3 Kingdom Plantae 4 Division: Magnoliophyta 5 Class Liliopsida 6 Order Poales 7 Family: Poaceae 8 Genus Oryza Nutrition Facts of rice in per 100 grams 1 Energy kcal 2 Carbohydrates 79.0 g 3 Fat 0.6 g 4 Protein 7.0 g 5 Vitamin B6 % 0.15 mg 12 6 Water 13.0 g Rice is one of the oldest cultivated crops, first mentioned in history as far back as 2800 BC in China. Rice is a staple crop and forms the foundation of the diet for many of the world s population, especially those living in Southern and Eastern Asia. There are a huge number of rice varieties such as long-grain, basmati and Arborio but only a few are grown widely. Basmati rice is a popular grain in Indian cooking. The word "basmati" translates to fragrant and describes the smell of the rice (16). Basmati rice originated in Page 73

3 India, Pakistan and China, but it is grown in the United States as well and is becoming widely available. Basmati rice is found in both brown (unprocessed) and white (processed) forms. Brown basmati rice retains more nutrients than the white form. Stored rice is being damaged by different insects, as a result considerable looses occur both qualitatively and quantitatively. The severity of infestation depends on moisture content and relative humidity in atmosphere. A brief review on genetic divergence in rice for yield contributing traits and quality parameters was reported by Sudharani, M., et al., (17).The two varieties which were investigated are- (A) Nafis Basmati Rice (Sample -1) Agro Overcseas Private Limited, Kakori road, Sonipath, Hryana. (B) Sudha Basmati Rice (Sample -2) International (P) LTS P.O.Box, 5 Indri Urad (Vigna Mungo L.) Black Uurad is originated in India, where it has been in cultivation from ancient times and is one of the most highly prized pulses of India. The coastal Andhra region in Andhra Pradesh is famous for black urad after paddy. The Guntur District ranks first in Andhra Pradesh for the production of black urad. Black urad has also been introduced to other tropical areas mainly by Indian immigrants. Classification of Urad 1 Hindi Name Urad 2 English Name Black urad & Green urad 3 Botanical Name Vigna Mungo 4 Kingdom Plantae 5 Order Fables 6 Family Fabacea 7 Subfamily Faboideae Nutrition Facts of urad in per 100 grams 1 Calories from Fat Calories Total Fat 3.6% 4 Total Carbohydrate 19% 5 Dietary Fiber 3% 6 Protein 48% Page 74

4 The two varieties of urad, investigated here, are- (A) Green Urad (Sample -3) (B) Black Urad (Sample -4) Black urad is a perfect combination of all nutrients which include 20 to 25%proteins, 40 to 47% starch, ash, fats, and carbohydrates and essential vitamins being a proper leguminous crop, Black urad has all the essential nutrients which it makes to turn into a fertilizer. With its ability to fix nitrogen it restores soil fertility as well, it proves to be a great rotation crop enhancing the yield of the main crop. For the best yields it should be grown in the seasons from mid September to October. Urad dal is 100% natural and hygienically processes. This dal is low in fat, zero cholesterol and is an excellent source of protein and fiber. Our pulses are detectable and highly nutritious. Whole urad dal derives its strong, earthy flavor from the black skins and is often used in curries. It is its nutritious value, which witness a large demand. Urad dhal has 24 gm of protein, 385 mg of phosphorous, 3.8 mg of iron, 154 mg of calcium, 0.42 mg of thiamine, 0.20 mg of riboflavin, 347 k calories, 2 mg of niacin, 39.8 mg of sodium and 800 mg of potassium in 100 gm. Vitamin C is not present in this dhal (18,19) Experimental Details The dust and other foreign materials were removed from the grains used in the present study. The grains were kept in an air-tight container to avoid any moisture gain or loss. The grains were then kept in a hot-air oven for 24 hours at 60 0 C to make the moisture content of all the grains same. Then, the different moisture contents 2, 4, 6, 8, and 10%, were made on wet basis. The samples were subjected to frequent agitation to aid uniform distribution of moisture. These samples were further kept in an air-tight container to avoid moisture loss. The temperature of the grains was varied by placing the sample holder in a speciallydesigned glass jacket through which heated oil was circulated using refrigerated circulator of Julabo (model number F-25, Germany). The accuracy of temperature measurement was up to ± C. The samples were kept in this condition for about 24 hours before the measurements were taken. The moisture content of the samples was determined by approved oven method (20). Thus, the prepared samples were measured Page 75

5 for the dielectric constant and the dielectric loss in the temperature range 30 0 C-51 0 C and at the frequency range 5 khz to 10MHz. 5.3 Results and Discussion Figure-(5.1) and figure-(5.2) respectively representing the variation of dielectric constant and dielectric loss with log 10 (frequency) at different percentage of moisture contents and at constant temperature 30 0 C for nafis basmati rice (sample-1) and sudha basmati rice (sample-2) respectively. Figure-(5.3) and-figure-(5.4) respectively showing the variation of dielectric constant and dielectric loss with different percentage of moisture contents at indicated frequencies and at constant temperature 30 0 C for both the sample-1 and sample- 2, while figure-(5.5) and figure- (5.6) respectively show the variation of dielectric constant and dielectric loss with temperature at indicated moisture contents and at constant frequency 50 khz for sample-1 and sample- 2. The variation of electrical conductivity with log 10 (frequency) at indicated moisture contents and at constant temperature 30 0 C for the sample-1 and sample-2 are shown in figure-(5.7). Figure-(5.8) shows the variation of electrical conductivity with percentage of moisture contents at indicated frequency and at constant temperature 30 0 C while Figure- (5.9) shows the variation of electrical conductivity with temperature at indicated moisture contents and at constant frequency 50 khz for both the samples 1 &2. Figure-(5.10) and figure-(5.11) respectively representing the variation of dielectric constant and dielectric loss with log 10 (frequency) at different percentage of moisture contents and at constant temperature 30 0 C for green urad (sample-3) and black urad (sample-4) respectively. Figure-(5.12) and figure-(5.13) respectively showing the variation of dielectric constant and dielectric loss with different percentage of moisture contents at indicated frequencies and at constant temperature 30 0 C for both the sample-3 and sample-4, while figure-(5.14) and figure-(5.15) show the variation of dielectric constant and dielectric loss with temperature at indicated moisture contents and at constant frequency 50 khz for sample-3 and sample-2. The variation of electrical conductivity with log 10 (frequency) at indicated moisture contents and at constant temperature 30 0 C for the sample-3 and sample-4 are shown in figure-(5.16). Figure-(5.17) shows the variation of electrical conductivity with percentage Page 76

6 of moisture contents at indicated frequency and constant temperature 30 0 C while Figure- (5.18) shows the variation of electrical conductivity with temperature at indicated moisture contents and at constant frequency 50 khz for both the samples 3 & Behaviour of Dielectric Constant and Dielectric Loss Factor for Sample- 1& Frequency Dependence Figure-(5.1) and figure-(5.2) respectively show the variation of dielectric constant and dielectric loss for sample-1 and sample-2 with log 10 (frequency) at indicated moisture contents and at constant temperature 30 0 C. It is observed that both the dielectric constant and dielectric loss of the complex permittivity decreases with increase in the frequencies. This exhibits dielectric dispersion in the material with frequency. The high values of dielectric constant at lower frequencies and high moisture content could be attributed to high mobility of dipole for free water state and electrode polarization. The high values of the dielectric loss can be attributed to high mobility of water dipole, electrode polarization and increase in ionic and surface conductivity reported by ISTA, (21) Moisture Dependence Figures-(5.3) and figure- (5.4) show the variation of dielectric constant and dielectric loss for sample-1 and sample-2 with moisture at indicated frequency and at constant temperature. From figure-(5.3) and figure-(5.4) it is clear that the complex dielectric permittivity increases with increase in the moisture content at a given frequency and temperature. It can be observed that the rate of increases in and is high at 5 khz, 50 khz and 2 MHz. The reason being that the water dipoles easily follow the applied field variations, at high moisture level and more water dipoles contribute to the polarization, due to high water mobility. At low moisture content, particularly below 5% both and of the complex permittivity are small because the distance between the water molecule and cell wall is very small and force of attraction is very large in the case of strong bound water state (monolayer). Therefore, the dielectric constant and dielectric loss both are small. When the moisture content increases beyond the 8%, bound water changes state from first (monolayer) to second (multilayer) type and add to the complex permittivity, which Page 77

7 shows a sharp increase in and for the moisture content at 10% for all the frequencies. This behaviour could be attributed to transition of bound water state from second (multilayer) to third state due to osmotic tension or free state of water at high moisture level reported by Nelsion, S.O., (22). At low frequency the ionic conductivity is high therefore for such moisture level and low frequencies, the dielectric losses are considerably high Temperature Dependence Figure-(5.5) and figure-(5.6) shows the variation of dielectric constant and dielectric loss for sample-1 and sample-2 with temperature at indicated moisture content and at constant frequency 50kHz.At different moisture levels dielectric constant and dielectric loss increase with increase in the temperature. The energetic status of the molecules and their aptitude to rotate with electric field changes to the permittivity due to the increase in the temperature and hence change in effective complex permittivity results in increase or the decrease of the water molecules contribution to the polarization of the medium. As the temperature increases the molecular mobility increases and the relaxation frequency, which is strongly related to the molecular mobility, increases. Increase in temperature also increases to the ionic conduction, leading to increase in dielectric loss. Thus, as temperature increases, both dielectric constant and dielectric loss increase. The increase in dielectric parameters with temperature at lower frequency and higher moisture content indicate the predominant effect of ionic conduction as well as molecular mobility. Therefore, under these conditions rate of increase of and with temperature are high and might be non-linear. The dielectric constant is less affected by the temperature than that of the dielectric loss because of increase in ionic conduction gives additional effect on dielectric loss factor, whereas dielectric constant is less or not at all affected by the ionic conduction. The similar variations are also seen in a recent study on temperature dependence of dielectric properties of pecan reported by Jones, R.R et al., (23) and for fruits in the range of 0 0 C 40 0 C (24). Page 78

8 5.3.2 Behaviour of Electrical Conductivity Figure-(5.7) shows the variation of electrical conductivity of sample-1 and sample-2 with log 10 (frequency) at indicated moisture content and at constant temperature at 30 0 C. Figure-(5.8) show the variation of electrical conductivity of sample-1 and sample-2 with moisture at indicated frequency and at constant temperature 30 0 C while figure-(5.9) show the variation of electrical conductivity of sample-1 and sample-2 with in temperature range 30 0 C-51 0 C at indicated moisture contents and at constant frequency50khz. From figure-(5.7) and figure-(5.8) it is clear that the electrical conductivity for sample-1 and sample-2 increases with increase in frequency and the moisture content at 30 0 C temperature. From figure-(5.9) it is observed that the variations with temperature are almost linear in general for all moisture levels at higher frequencies, however nonlinearity is present at lower frequencies. Fig.5.1: Variation of dielectric constant of sample-1and sample-2 at indicated moisture content and at constant temperature 30 0 C. Page 79

9 Fig.5.2: Variation of dielectric loss of sample-1and sample-2 at indicated moisture content and at constant temperature 30 0 C. Fig.5.3: Variation of dielectric constant of sample-1and sample-2 with moisture percentage at indicated frequency and at constant temperature 30 0 C. Fig.5.4: Variation of dielectric loss of sample-1and sample-2 with moisture percentage at indicated frequency and at constant temperature 30 0 C. Fig.5.5: Variation of dielectric constant of sample-1and sample-2 with temperature at indicated moisture and at constant frequency 50 khz. Page 80

10 Fig.5.6: Variation of dielectric loss of sample-1and sample-2 with temperature at indicated moisture and at constant frequency 50 khz. Fig.5.7: Variation of electrical conductivity of sample-1and sample-2 at indicated moisture content and at constant temperature 30 0 C. Fig.5.8: Variation of electrical conductivity of sample-1 and sample-2 with moisture percentage at indicated frequency and constant temperature 30 0 C. Page 81

11 Fig.5.9: Variation of electrical conductivity of sample-1 and sample-2 with temperature at indicated moisture content and at constant frequency 50 khz Behaviour of Dielectric Constant and Dielectric Loss Factor for Sample-3 and Frequency Dependence Figure-(5.10) and figure-(5.11) show the variation of dielectric constant and dielectric loss for sample-3 and sample-4 with log 10 (frequency) at indicated moisture contents and at constant temperature 30 0 C. It is observed that both the dielectric constant and dielectric loss of the complex permittivity decreases with increase in the frequency. The possible reason is similar to as discuss earlier Moisture Dependence Figure-(5.12) and figure-(5.13) show the variation of dielectric constant and dielectric loss for sample-3 and sample-4 with moisture at indicated frequency and at constant temperature. From figure-(5.12) and figure-(5.13) it is clear that the complex dielectric permittivity increases with increase in the moisture content at a given frequency and temperature. It can be observed that the rate of increases of and is more for higher frequencies. The reason as already been discussed in case of rice. When the moisture content increases beyond the 8%, bound water changes state from first (monolayer) to second (multilayer) type and add to the complex permittivity, which shows a sharp increase in and for the moisture content at 10% for all the frequencies. This behaviour could be attributed to transition of bound water state from second (multilayer) to third state due to osmotic tension or Free state of water at high Page 82

12 moisture level reported by Nelson, S.O., (22). At low frequency the ionic conductivity is high therefore for such moisture level and low frequencies, the dielectric losses are considerably high Temperature Dependence Figure-(5.14) and figure-(5.15) show the variation of dielectric constant and dielectric loss for sample-3 and sample-4 with temperature at indicated moisture content and at constant frequency 50 khz. Dielectric constant and dielectricloss increases with increase in the temperature for both the samples 3 and 4. At lower moisture lavels, it is found that the relationship between the dielectric constant, dielectric loss and temperature to be linear for all the frequencies.morever it is also noticed that slight non-linearity in the curve at high moisture level and low friquencies particularly at 5 khz. Ina recent study on dielectric properties of some oil seeds at different concentratin of moisture content and micro-fertilizer have reported similar variation in the temperature range of C (25). This effect is due to the fact that temperature change or modify the activation state of the molecules and theiraptitude to rotate with the electric field Behaviour of Electrical Conductivity Figure-(5.16) shows the variation of electrical conductivity of sample-3 and sample-4 with log 10 (frequency) at indicated moisture content and at constant temperature at 30 0 C. Figure-(5.17) show the variation of electrical conductivity of sample-3 and sample-4 with moisture at indicated frequency and at constant temperature 30 0 C while figure-(5.18) show the variation of electrical conductivity of sample-3 and sample-4 with in temperature range 30 0 C-51 0 C at indicated moisture contents and at constant frequency 50kHz. From figure-(5.16) and figure-(5.17) it is clear that the electrical conductivity for sample-3 and sample-4 increases with increase in frequency and the moisture content at 30 0 C temperature. From figure-(5.18) it is observed that the variations with temperature are almost linear in general for all moisture levels at higher frequencies, however nonlinearity is present at lower frequencies. The reason is already discussed in chapter II. This type of similarty is well expected as the conductivity has been evaluated using dielectric data. Page 83

13 Fig.5.10: Variation of dielectric constant of sample-3 and sample-4 at indicated moisture content and at constant temperature 30 0 C Fig.5.11: Variation of dielectric loss of sample-3and sample-4 at indicated moisture content and at constant temperature 30 0 C. Fig.5.12: Variation of dielectric constant of sample-3and sample-4 with moisture percentage at indicated frequency and at constant temperature 30 0 C. Page 84

14 Fig.5.13: Variation of dielectric loss of sample-3and sample-4 with moisture percentage at indicated frequency and at constant temperature 30 0 C. Fig.5.14: Variation of dielectric constant of sample-3and sample-4 with temperature at indicated moisture and at constant frequency 50 khz. Fig.5.15: Variation of dielectric constant of sample-3and sample-4 with temperature at indicated moisture and at constant frequency 50 khz. Page 85

15 Fig.5.16: Variation of electrical conductivity of sample-3 and sample-4 with log 10 (frequency) at indicated moisture content and at constant temperature 30 0 C. Fig.5.17: Variation of electrical conductivity of sample-3 and sample-4 with moisture percentage at indicated frequency and at constant temperature 30 0 C. Fig.5.18: Variation of electrical conductivity of sample-3 and sample-4 with temperature at indicated moisture content and at constant frequency 50 khz. Page 86

16 5.4 Conclusions The results of the present study clearly indicate that the dielectric constant and the dielectric loss are dependent on frequency, temperature and moisture levels of the samples. The dielectric constant can be used as a measure of salt and water content in the grains. It can be concluded that moisture level affects the electrical properties to a large extent. Here electrical properties can be used to quality control of selected grains. The electrical properties are also used for safe and long time preservation of grains. 5.5 References 1. Nelson, S. O., Use of electrical properties of grain moisture measurement J.Microwave power 12(1), Nelson, S. O., Charity, L. F., Frequency dependence of energy absorption by insects and grains in electric fields. Transactions of ASAE 15(6), Nelson, S. O., Dielectric properties of some grain and seed. ASE 8(1): Ragni, L., and Zhang, L., Project no.18- based on dielectric properties methodologies to determine nondestructively the fruit internal quality. 5. Nelson, S.O., Netile, G. E., and Stetson, L. E., Effect of Radio frequency electrical treatment on germination of vegetable seeds. J. Amer. Soc. Hort. Sci. 95, Hamid, M. A. K., and Boulanger, R. J., A new Method for the control of moisture and insect infections of grain by microwave power. J. Microwave power 4 (1), Norris, K. H., and Brant, A.W., Radio frequency TAS a means of grading eggs. Food Tech. 6(6), Pushpanngadan. P., and Singh, S. P., Chap. 22-Poppy. Handbook of herbs and spices. Page 87

17 9. Wendell, Q. Sum., Dielectric relaxation of water and water-plasticized bimolecular in relation to cellular water organization, cytoplasmic viscosity and desiccation tolerance in recalcitrant seed tissues. Plant Physiology 24: Elena, M., Gonalez-Bento and Felix Perez-Garcia, Cryo. Letter 22: Konsta, A., P., Pissis, A., and Ratkovie, S., J. Bio-Physical, 70: Dela, Cruz, N., and Khush, G. S., Rice grain quality evaluation procedures. In Aromatic rices, (eds. R.K. Singh, U.S. Singh and G.S. Khush),. Publisher, Oxford and IBH publishing Co. Pvt. Ltd., New Delhi, Calcutta , 13. You, K. Y., Jalani, S. N. A., Abbas, Z., and You, L. L., Application of bandpass lter as a sensorfor rice characterization," International Conference on Computer Applications and IndustrialElectronics (ICCAIE 2010), 570{573, Kuala Lumpur, Malaysia. 14. You, K. Y., Salleh, J., Abbas, Z., and You, L. L., 2011.Cylindrical Slot Antennas for Monitoring the Quality of Milled Rice PIERS Proceedings, Suzhou, China, September 12-16, 15. Ahmed, J., Ramaswamy, H. S., Raghavan, G. S. V., Dielectric properties of Indian Basmati rice flour slurry. J. Food Eng., 80, www. foodreference.com 17. Sudharani, M., Prasanna Rajesh A. Jayalakshmi V. and Rajyalakshmi K A brief review on genetic divergence in rice for yield contributing traits and quality parameters.internationaljournal of applied abiology and pharmscuitical technology, Vol 3(4) (accepted). 18. Kanade, R. S.,2006. Post-Harvest Profile of Black Gram, Government of India Ministry of Agriculture (department of agriculture and cooperation) Directorate of Marketing and Inspection Branch Head Office Nagpur sept. 8th, Maskus, H., Pulse Processing, Functionality and Application Literature Review,Winnipeg, Manitoba January 27, USDA, 1971.Oven methods for determining moisture content of agricultural commodities equipments manual. GR Instruction. Grain Division, Consumer and Marketing Service Equipment manuals., 916,6. Page 88

18 21. ISTA, International rules for seed testing. International Seed testing Association. Seed Science and technology 24, supplement. 22. Nelsion, S.O., RF and microwave dielectric properties.trans. Of ASE 22(6), Jones, R.R. N., Bussey. H. E., Little. W.E. and Metzeker. R. F., Electrical Characteristics of corn, wheat and Soya in the MHz range. NBSIR , National bureau of standards, U.S. Department Commerce. 24. Lawrence K. C., et. al., Temperature dependence of the dielectric properties of Pecans. Trans. Of ASAE. 35(5), Singh, S. P., Kumar, P., Manohar, R., Shukla, J. P.,2006. Dielectric properties of some oil seeds at different concentration of moisture content and micro fertilizer. International journal of agricultural research 1(3): Page 89