Drying Kinetics of Onion Slices in a Hot-air Dryer

  • Lee, Jun-Ho (Department of Food Science and Engineering, Daegu University) ;
  • Kim, Hui-Jeong (Department of Food Science and Engineering, Daegu University)
  • Published : 2008.09.30


Onion slices were dehydrated in a single layer at drying air temperatures ranging from $50{\sim}70^{\circ}C$ in a laboratory scale convective hot-air dryer at an air velocity of 0.66 m/s. The effect of drying air temperature on the drying kinetic characteristics were determined. It was found that onion slices would dry within $210{\sim}460\;min$ under these drying conditions. Moisture transfer during dehydration was described by applying the Fick's diffusion model and the effective diffusivity changed between $1.345{\times}10^{-8}$ and $2.658{\times}10^{-8}\;m^2/s$. A non-linear regression procedure was used to fit 9 thin layer drying models available in the literature to the experimental drying curves. The Logarithmic model provided a better fit to the experimental drying data as compared to other models. Temperature dependency of the effective diffusivity during the hot-air drying process obeyed the Arrhenius relationship with estimated activation energy being 31.36 kJ/mol. The effect of the drying air temperature on the drying model constants and coefficients were also determined.


  1. Kim SJ, Kim GH. 2006. Quantification of quercetin in different parts of onion and its DPPH radical scavenging and antibacterial activity. Food Sci Biotechnol 15: 39-43
  2. Pathare PB, Sharma GP. 2006. Effective moisture diffusivity of onion slices undergoing infrared convective drying. Biosyst Eng 93: 285-291
  3. Kumar A, Tiwari GN. 2007. Effect of mass on convective mass transfer coefficient during open sun and greenhouse drying of onion flakes. J Food Eng 79: 1337-1350
  4. Das S, Das T, Rao PS, Jain RK. 2001. Development of an air recirculating tray dryer for high moisture biological materials. J Food Eng 50: 223-227
  5. Kalbasi M. 2003. Heat and moisture transfer model for onion drying. Drying Technol 21: 1575-1584
  6. Mazza G, LeMaguer M. 1980. Dehydration of onion: some theoretical and practical considerations. J Food Technol 15: 181-194
  7. Kaymak-Ertekin F, Gedik A. 2005. Kinetic modeling of quality deterioration in onions during drying and storage. J Food Eng 68: 443-453
  8. Raspusas RS, Driscoll RH. 1995. The thin-layer drying characteristics of white onion slices. Drying Technol 13: 1905-1931
  9. Jain D, Pathare PB. 2004. Selection and evaluation of thin layer drying models for infrared radiative and convective drying of onion slices. Biosyst Eng 89: 289-296
  10. AOAC. 1990. Official Method of Analysis. Association of Official Analytical Chemists (No. 934.06), Arlington, VA
  11. O'Callaghan JR, Menzies DJ, Bailey PH. 1971. Digital simulation of agricultural dryer performance. J Agr Eng Res 16: 223-144
  12. Page G. 1949. Factors influencing the maximum rates of air-drying shelled corn in thin layer. MS Thesis. Purdue University, Purdue, USA
  13. Overhults DD, White GM, Hamilton ME, Ross IJ. 1973. Drying soybeans with heated air. T ASAE 16: 195-200
  14. Henderson SM, Pabis S. 1961. Grain drying theory. II. Temperature effects on drying coefficients. J Agr Eng Res 6: 169-174
  15. Yagcioglu A, Degirmencioglu A, Cagatay F. 1999. Drying characteristic of laurel leaves under different conditions. Proceedings of the 7th International Congress on Agricultural Mechanization and Energy, 26-27 May, Adana, Turkey. Faculty of Agriculture, Cukurova University. p 565-569
  16. Henderson SM. 1974. Progress in developing the thin-layer drying equation. T ASAE 17: 1167-1168, 1172
  17. Sharaf-Eldeen YI, Blaisdell JL, Hamdy MY. 1980. A model for ear corn drying. T ASAE 5: 1261-1265
  18. Sharaf-Eldeen YI, Hamdy MY, Blaisdell YL. 1979. Mathematical description of drying fully exposed grains. ASAE Paper No. 79-3034. St Joseph, MI, ASAE
  19. Crank J. 1975. The mathematics of diffusion. 2nd ed. Clarendon Press, Oxford, UK
  20. Togrul İT, Pehlivan D. 2003. Modelling of drying kinetics of single apricot. J Food Eng 58: 23-32
  21. Kaleemullah S, Kailappan R. 2006. Modelling of thin-layer drying kinetics of red chillies. J Food Eng 76: 531-537
  22. Wang J, Sun J, Liao X, Chen F, Zhao G, Wu J, Hu X. 2007. Mathematical modeling on hot air drying of thin layer apple pomace. Food Res Int 40: 39-46
  23. Giri SK, Prasad S. 2007. Drying kinetics and rehydration characteristics of microwave-vacuum and convective hot-air dried mushrooms. J Food Eng 78: 512-521.23
  24. Kaleemullah S, Kailappan R. 2007. Monolayer moisture, free energy change and fractionation of bound water of red chillies. J Stored Prod Res 43: 104-110
  25. Sarsavadia PN, Sawhney RL, Pangavhane DR, Singh SP. 1999. Drying behaviour of brined onion slices. J Food Eng 40: 219-226
  26. Akgun NA, Doymaz I. 2005. Modeling of olive cake thin-layer drying process. J Food Eng 68: 455-461
  27. Sacilik K, Elicin AK. 2006. The thin layer drying characteristics of organic apple slices. J Food Eng 73: 281-189
  28. 2008. Convective drying Kinetics of strawberry. Chem Eng Process 47: 914-919
  29. Lopez A, Iguaz A, Esnoz A, Virseda P. 2000. Thin-layer drying behaviour of vegetable wastes from wholesale market. Drying Technol 18: 995-1006
  30. Rizvi SSH. 1986. Thermodynamic properties of foods in dehydration. In Engineering properties of foods. Rao MA, Rizvi SSH, eds. Marcel Dekker Inc., New York, p 190-193
  31. Arora S, Shivhare US, Ahmed J, Raghavan GSV. 2003. Drying kinetics of Agaricus bisporus and Pleurotus florida mushrooms. T ASAE 46: 721-724
  32. Kaya A, Aydin O, Demirtas C. 2007. Drying kinetics of red delicious apple. Biosyst Eng 96: 517-524
  33. Sacilik A, Elicin AK, Unal G. 2006. Drying kinetics of Uryani plum in a convective hot-air dryer. J Food Eng 76: 362-368
  34. Gogus F, Maskan M. 1999. Water adsorption and drying characteristics of okra (Hibiscus esculentus L.). Drying Technol 17: 883-894
  35. Kaymak-Ertekin F. 2002. Drying and rehydrating kinetics of green and red pepper. J Food Sci 67: 168-175
  36. Kumar DGP, Hebbar HU, Ramesh MN. 2006. Suitability of thin layer models for infrared-hot air-drying of onion slices. Lebensm-Wiss Technol 39: 700-705
  37. Sharma GP, Verma RC, Pathare PB. 2005. Thin layer infrared radiation drying of onion slice. J Food Eng 67: 361-366
  38. Wang J. 2002. A single-layer model for far-infrared radiation drying of onion slices. Drying Technol 20: 1941-1953
  39. Cronin K, Kearney S. 1998. Monte Carlo modelling of a vegetable tray dryer. J Food Eng 35: 233-250
  40. Karathanos VT. 1999. Determination of water content of dried fruits by drying kinetics. J Food Eng 39: 337-344
  41. Doymaz İ. 2007. The kinetics of forced convective air-drying of pumpkin slices. J Food Eng 79: 243-248
  42. Belghit A, Kouhila M, Boutaleb BC. 2000. Experimental study of drying kinetics by forced convection of aromatic plants. Energ Convers Manage 41: 1303-1321
  43. Akpinar EK, Bicer Y, Yildiz C. 2003. Thin layer drying of red pepper. J Food Eng 59: 99-104
  44. Wang Z, Sun J, Chen F, Liao X, Hu X. 2007. Mathematical modelling on thin layer microwave drying of apple pomace with and without hot air pre-drying. J Food Eng 80: 536-544
  45. Kaleemullah S, Kailappan R. 2005. Drying kinetics of red chillies in rotary dryer. Biosyst Eng 92: 15-23
  46. Doymaz I. 2005. Drying behaviour of green beans. J Food Eng 69: 161-165

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