Chapter-IV Comparative Dielectric Study of Black Pepper and White Pepper (Piper Nigrum L.) 4.1 Introduction Black Pepper (Piper nigrum L), the King of Spices, is the most important and most widely used spice in the world. It belongs to the family of piperaceae and grows in the South Western region of India (Kerala, parts of Karnataka, Tamil Nadu and Goa). Apart from India other major producers of the black pepper and the white pepper are- Vietnam, Sri Lanka, Malaysia, Indonesia and few other countries. White pepper (Piper nigrum) is also a popular variety of pepper, also known as pepper corn; it also belongs to the family of Piperaceae. Both black pepper and white pepper are produced from the same barriers through different processes. For black pepper barriers are harvested when they are greenish yellow, then they are dried in sun, on the other hand for white pepper barriers are harvested when they are red or reddish orange. These ripe barriers are kept in water for some days, thus their skin becomes soft, which can be removed easily. They are also dried in sun. Black pepper has greater percentage of share in spice market than thatof other spices (1). Black Pepper is used in traditional medicinal systems like ayurveda, Siddha and Unani (2, 3). It is used in curing asthma, cough, heart diseases, night blindness, urinary disorders and many pains. Black pepper as drug in the Indian and Chinese systems of medicine is well documented (4, 5). Per 100g of black pepper contains, water 9.5-12.0g, protein 10.9-12.7g, starch 25.8-44- 8g, fiber 9.7-17.2g, ash 3.4-6.0g, piperrine C 17 H 19 O 3 N 4.9-7.7%, essential oils mainly monoterpene and sesquiterpene 1.0-1.8% on the other hand per 100g of white pepper contains water 9.5-13.7g, protein 10.7-12.4g, starch 53.9-60.4g, fiber 3.5-4.5g, ash 1.0-2.8g, piperrine C 17 H 19 O 3 N 5.5-5.9%, essential oils mainly monoterpene and sesquiterpene 0.5-0.9% (6). Literature survey reveals that Prashant B. Shyamkumar et al. reported antidiarrhoeal effect of black pepper (7, 8, 9), Murlidhar Meghwal et al., reported DSC and thermal diffusivity of black pepper and its volatile oils (10). Amar Singh et al., showed that Page 61
piperine (an alkaloid), a component of black pepper is a good bioenhancer (11). In recent reviews Murlidhar et al. showed that black pepper has carminative, anti cancer, cholesterol lowering, anti pyretic and immune enhancer properties (12, 13), while Shabnam Ashouri et al. reported insecticidal activities of black pepper (14). Most of the researchers have focused their studies on the medicinal properties of the black pepper seeds, but no study has been done to explore the physical properties of black pepper and white pepper, so it is worthwhile to study comparative dielectric properties of black pepper and white pepper. 4.2 Material and Methods 4.2.1 Black Pepper and White Pepper English Name : Black pepper, White pepper Hindi Name : Kali mirch, Safed mirch Botanical Name : Piper nigrum L Family name : Piperaceae. 4.2.2 Constituents The components contains per 100gram of black and white pepper Component Black pepper White pepper Water 9.5-12.0g 9.5-13.7 g Protein 10.9-12.7g 10.7-12.4g Starch 25.8-44.8g 53.9-60.4g Fiber 9.7-17.2g 3.5-405g Ash 3.4-6.0g 1.0-2.8g Piprine (pungent) 4.9-7.7 5.5-5.9 4.2.3 Experimental Details The black pepper and white pepper seeds were purchased from a local market. Before the experiments, the seeds were cleaned manually to remove foreign matter. The moisture contents in black pepper and white pepper seeds were determined on wet basis. The moisture contents were adjusted by adding distilled water and conditioning of the samples at 20ºC. The samples were subjected to frequent agitation to aid uniform distribution of moisture. These were stored in sealed jars at 20ºC and permitted to reach Page 62
at room temperature (30ºC) in sealed jars before opening for measurements. The samples were kept in this condition for about 28 hours before the measurements were taken. The capacitances (C M ) and dissipation factor (D M ) measurements have been done with the help of impedance/gain phase analyzer (model No. HP-4194A, frequency range 100Hz to 40 MHz) using a coaxial cylindrical capacitor. The sample holder has been silver plated to reduce dissipation losses. It was calibrated by using standard liquids (Benzene and Methanol) and error in measurement for dielectric constant ( ) was found to be 1% and that for dielectric loss ( ) was 1.5%. The formulae for the measurement of dielectric constant and dielectric loss have already been published elsewhere (15, 16, 17). The dielectric parameters and conductivity have been calculated with the help of the mathematical relations given in chapter II. 4.3 Results and Discussion 4.3.1 Variation of Dielectric Constant of Black and White Pepper 4.3.1.1 Frequency Dependence Figure-(4.1a) and figure-(4.1b) shows the variation of dielectric constant with log 10 (frequency) at different percentage of moisture contents at constant temperature 30 0 C for both the black pepper and white pepper. From figure-(4.1a) and figure-(4.1b) it is clear that, as frequency increases the dielectric constant of both the black and white pepper decreases and it is also clear that, the dielectric constant of black pepper is greater than that of white pepper at all moisture contents. The high values of dielectric constant may be because of high starch content in white pepper. The more starch molecules bind more water molecules and reduce the free water content of the system. This has already been explained by some researcher (18). Page 63
Fig.4.1: Frequency dependence of dielectric constant of black pepper and white pepper at indicated moisture contents and 30 0 C. 4.3.1.2 Moisture Dependence Figure-(4.2a) and figure-(4.2b) shows the variation of dielectric constant with percentage moisture contents at constant temperature 30 0 C for both the black pepper and white pepper. From figure-(4.2a) and figure-(4.2b) it is clear that, as percentage moisture content increases the dielectric constant of both the black pepper and white pepper increases and it can also be seen that, the dielectric constant of black pepper is greater than that of white pepper. This is because the water content in white pepper is slightly higher than black pepper (18). From the figure it can also be inferred that 6% moisture content is the critical moisture content beyond which dielectric constant increases. Fig.4.2: Moisture dependence of dielectric constant of black pepper and white pepper at Indicated frequencies and constants temperature30 0 C. Page 64
4.3.1.3 Temperature Dependence Figure-(4.3a) and figure-(4.3b) shows the variation of dielectric constant with temperature at constant frequency 50 khz for both the black pepper and white pepper. From figure-(4.3a) and figure-(4.3b) it is clear that, as temperature increases the dielectric constant of both the black pepper and white pepper increases and it is also clear that, the dielectric constant of black pepper is higher than that of white pepper. As temperature increases the denaturization of protein may take place which increases charge asymmetry and large polarization. Thus, dielectric constant increases and in case of black pepper protein content is more than in white pepper so black pepper has higher dielectric constant than white pepper at higher temperature. Here the effect of protein denaturization has higher impact on dielectric constant than starch at higher temperatures (18). Fig.4.3: Temperature dependence of dielectric constant of black pepper and white pepper at indicated moisture content and constants frequency 50 khz. 4.3.2 Variation of Dielectric Loss Factor of Black and White Pepper 4.3.2.1Frequency Dependence Figure-(4.4a) and figure-(4.4b) shows the variation of dielectric loss with log 10 (frequency) at different percentage moisture contents at indicated temperature 30 0 C for both the black pepper and white pepper. From figure-(4.4a) and figure-(4.4b) it is clear that, as frequency increases the dielectric loss for both the black pepper and white pepper decreases and it is also clear that, the dielectric loss of black pepper is greater than that of white pepper. Here it can also be seen that the nature of variation of dielectric loss for both the samples is same but the dielectric loss in case of black pepper is much higher than that of white pepper, which may be because white pepper contains more essential Page 65
oils than black pepper (6) and according to Ryynanen as lipid contents increase dielectric properties change (19). Fig.4.4: Frequency dependence of dielectric loss of black pepper and white pepper at indicated moisture contents and 30 0 C. 4.3.2.2 Moisture Dependence Figure-(4.5a) and figure-(4.5b) shows the variation of dielectric loss with percentage moisture content at indicated temperature 30 0 C for both the black pepper and white pepper. From figure-(4.5a) and figure-(4.5b) it is clear that, as percentage moisture increases the dielectric loss for both the black pepper and white pepper increases and it is also clear that, the dielectric loss of black pepper is greater than that of white pepper. In both the cases the dielectric loss is increasing beyond 6% of moisture content which indicates that this is the region of critical moisture content, below which water is in bound state and above it is in free state. Fig.4.5: Moisture dependence of dielectric loss of black pepper and white pepper at indicated frequencies and constant temperature 30 0 C. Page 66
4.3.2.3 Temperature Dependence Figure-(4.6a) and figure-(4.6b) shows the variation of dielectric loss with temperature at constant frequency 50 khz for both the black pepper and white pepper. From figure- (4.6a) and figure-(4.6b) it is clear that, as temperature increases the dielectric loss for both the black pepper and white pepper increases and it is also clear that, the dielectric loss of black pepper is greater than that of white pepper. We have already discussed that upto 6% water is in bound state and the dielectric properties increases with increase in temperature (20). Beyond 6% of moisture content the free water content increases, and then combined effect of bound water and free water on dielectric properties is observed. Fig.4.6: Temperature dependence of dielectric loss of black pepper and white pepper at indicated moisture contents and constant frequency 50 khz. 4.3.3 Behavior of Electrical Conductivity 4.3.3.1 Frequency Dependence Figure-(4.7a) and figure-(4.7b) shows shows the variation of electrical conductivity with log 10 (frequency) at different percentage moisture contents at constant temperature 30 0 C for both the black and white pepper. From figure-(4.7a) and figure-(4.7b) shows it is clear that, as frequency increases the electrical conductivity of both the black and white pepper increases and it is also clear that, the electrical conductivity of black pepper is greater than that of white pepper. Page 67
Fig. 4.7: Frequency dependence of electrical conductivity of black pepper and white pepper at indicated moisture contents and constant temperature at 30 0 C. 4.3.3.2 Moisture Dependence Figure-(4.8a) and figure-(4.8b) shows the variation of electrical conductivity with percentage moisture contents at constant temperature 30 0 C for both the black and white pepper. From figure- (4.8) it is clear that, as percentage moisture increases the electrical conductivity of both the black and white pepper increases and it is also clear that, the electrical conductivity of black pepper is greater than that of white pepper at low frequency (5, 10and 30 khz). (a) black pepper (b) white pepper Fig.4.8: Moisture dependence of electrical conductivity of black pepper and white pepper at indicated moisture contents and constant temperature at 30 0 C. 4.3.3.3 Temperature Dependence Figure-(4.9a) and figure-(4.9b) shows the variation of electrical conductivity with temperature at a constant frequency of 50 khz for both the black and white pepper. From Page 68
figure-(4.9) it is clear that, as frequency increases the electrical conductivity of both the black and white pepper increases and it is also clear that, the electrical conductivity of black pepper is greater than that of white pepper. Fig.4. 9: Temperature dependence of electrical conductivity of black pepper and white pepper at indicated moisture contents and constant frequency 50 khz. 4.4 Conclusions The dielectric constant and loss factor were shown to be dependent on the moisture content, and frequency of the applied electric field. The moisture content had a dominating influence on these dielectric properties because of related effect of moisture changes. The dielectric constant and loss factor increased with increase in the moisture content. The changes in dielectric constant and loss factor were observed to be greater at lower frequencies than at higher frequencies. The frequency dependence of the loss factor was less regular than that of the dielectric constant. Dielectric properties of black pepper and white pepper samples as a function of frequency, moisture and temperature were measured with an open-ended coaxial-line probe, impedance gain phase analyzer, and suitable sample temperature control equipment. Both dielectric constant and loss factor of black pepper and white pepper decreased with increases in frequency over the detected frequency range from 5kHz to 10MHz. At those frequencies, ionic conduction was the predominant factor that influences dielectric loss for samples. The dielectric constant and loss factor increased with increasing moisture content from 0% to 10% and also increased with increase in temperature in the range from 20 0 C to 50 0 C. Higher moisture contents and temperatures Page 69
had greater influence on permittivity than lower moisture contents and temperatures. These results may be useful in dielectric heating applications, and in developing potential new dielectric property based moisture meters. 4.5 References 1. Atal C. K., Zutshi U. and Rao P. G., 1981. Scientific evidence of the role of Ayurvedic herbals on bioavailability of drugs. J. of Ethnopharm, 4, 229-233. 2. Perry L. M., 1980. Medicinal Plants of East and Southeast Asia: Attributed properties and uses: MIT Press Cambridge. 3. Majeed and Prakash L., 2000. The Medicinal Uses of Pepper. Inter. Pepper News, 25(1), 23-31. 4. Kurup, P. N. V., Ramadas, V. N. K., and Joshi, P., 1979. Handbook of Medicinal Plants, New Delhi, 143 pp. 5. Atal, C. K., Dhar, K. L and Singh, J., 1975. The Chemistry of Indian Piper. Lloydia, 38, 250 264. 6. Nelson S. and Cannon-Eger K.T., 2011. Form and forestry Production and Marketing Profile for Black pepper, (Piper Nigrum), (USDA-WSARE) (http://agroforestry.net/scps). 7. Shamkuwar P. B., 2012. Significance of Black pepper in Ayurvedic antidiarrhoeal formulation. Journal of Chemical and Pharmaceutical Research, 4(4), 2162-2166. 8. Shamkuwar P. B. and Shahi S. R., 2012. Effect of Black pepper on antidiarrhoeal activity of an Ayurvedic formulation: Kutajarishta. Asian Journal of Plant Science and Research, 2 (3), 284-289. 9. Shamkuwar P. B., Shahi S. R. and Jadhav S. T., 2012. Evaluation of antidiarrhoeal effect of Black pepper (Piper nigrum L.). Asian Journal of Plant Science and Research, 2 (1), 48-53. 10. Meghwal M. and Goswami T. K., 2011. Thermal Properties Of Black Pepper and Its Volatile Oil.International Journal of Advanced Biotechnology and Research, 2(3), 334-344, 11. Singh A. and Deep A., 2011. Piperine: A Bioenhancer. International Journal of Pharmacy Research and Technology, 1(1), 01-05. Page 70
12. Meghwal M. and Goswami T. K., 2012. Chemical Composition, Nutritional, Medicinal and Functional Properties of Black Pepper: A Review, Scientific Reports, 1 (2). 13. Meghwal M. and Goswami T. K., 2012. Nutritional Constituent of Black Pepper as Medicinal Molecules: A Review, Scientific Reports, 1(1). 14. Ashouri S. and Shayesteh N., 2009. Insecticidal Activities of Black Pepper and Red Pepper in Powder Form on Adults of Rhyzopertha Dominica (F.) and Sitophilus Granarius (L.). Pak. Entomol., 31(2), 122, 15. Khan M. S., Chandel V. S. and Manohar R., 2012. Electrical Properties of Argemone Seeds at Variable Moisture Contents, 2(19), 205-212. 16. Khan M. S., Chandel V. S., Manohar R. and Shukla J. P., 2012. Study of Dielectric Properties of Fenugreek Seeds (Trigonella Foenum Graecum), Seed Science and Plant Breeding, 60, accepted. 17. Chandel V. S., Rahman A., Shukla J. P. and Manohar R., 2012. Effect of Fungicide Treatment on Dielectric Properties of Few Coarse- Cereals Over the Frequency Range 0.01 to 10 MHz. Walailak J Sci & Tech., 9(3): 217 227. 18. Ndife M., Summu G. and Bayindirli L., 1998. Dielectric properties of six different species of starch at 2450 MHz, Food Res. International, 31, 43-52, 19. Ryynanen, S. 1995. The electromagnetic properties of food materials: A review of basic principles, Journal of Food Engineering, 26, 409-429. 20. Sahin S. and Summu S. G., 2006. Physical Properties of Food, Springer Ed. 181-183. Page 71