Journal of Food Science and Technology

, Volume 52, Issue 8, pp 4819–4829 | Cite as

Batch uniformity and energy efficiency improvements on a cabinet dryer suitable for smallholder farmers

  • Marcelo PrecoppeEmail author
  • Serm Janjai
  • Busarakorn Mahayothee
  • Joachim Müller
Original Article


Drying can add value, facilitate transport and extend the storage life of agro-products; therefore, in developing countries with poorly established cool-chains, drying is particularly effective. Furthermore, drying within small-scale village-based enterprises contributes to rural development. However, most equipment suitable to such operations yields a product of non-uniform quality and shows low levels of energy efficiency. The aim of this research was to improve the batch uniformity and the energy efficiency of a cabinet dryer suitable for smallholder farmers. Experiments were carried out with the cooperation of a dryer manufacturer and a group of users. On each trial 144.5 kg of peeled and deseeded litchis were placed at the dryer’s 17 trays, that were stacked atop each other. Moisture content (wet basis) was reduced from 87 to 23 % in about 15.5 h. It was found that a low-cost modification to the dryer chamber’s air inlet was able to improve heat distribution and increase the uniformity of the fruit’s moisture content. In the original design, at the end of the drying process, moisture content of the fruits on the top tray was 38 % while at the bottom tray was 12 %. The modification to the dryer reduced this disparity and the final moisture content of the fruits placed at the top tray was 25 % while at the bottom tray was 21 %. In addition, the modification reduced the dryer’s air mass flow from 0.3 to 0.1 kg s−1 without jeopardizing drying forces, consequently the dryer energy efficiency increased from 33 to 42 %.


Convection dryer Hot-air dryer Heat consumption Product homogeneity Moisture content Lychee 





Isosteric heat of sorption


Liquefied petroleum gas



\( \overset{\cdot }{m} \)

Mass flow

\( {\overset{\cdot }{n}}_{\mathrm{w}} \)

Drying rate


Undefined variable





\( \overset{\cdot }{Q} \)





Air velocity

\( \overset{\cdot }{w} \)

Evaporation rate


Moisture content


Absolute humidity

Greek letters


Uniformity index


Energy efficiency


Latent heat of vaporisation


Relative humidity



Drying air


Dry matter


Dryer’s air duct






Dryer’s tray





This study was conducted as part of an international program named “Sustainable Land Use and Rural Development in the Mountainous Regions of Southeast Asia” (SFB 564). It was funded by the Deutsche Forschungsgemeinschaft (DFG) and co-funded by the National Research Council of Thailand (NRCT). We should express gratitude to the Hmong Mae Sa Valley Cooperative, and to Likhitchewan Co., Ltd, for taking part in this research study, and would also like to thank the Faculty of Agriculture at Chiang Mai University for hosting the SFB 564 office and supporting the project’s laboratory work.


  1. Anupunt P, Sukhvibul N (2005) Lychee and longan production in Thailand. Acta Horticult (ISHS) 665:53–60Google Scholar
  2. Araya-Farias M, Ratti C (2008) Dehydration of foods. In: Ratti C (ed) Advances in food dehydration. Contemporary food engineering. CRC Press, Boca Raton, pp 1–36CrossRefGoogle Scholar
  3. ASABE (2008) ASAE S358.2 DEC1988 (R2008) Moisture measurements—forages. In: American Society of Agricultural and Biological Engineers (ed) ASABE standards 2008: standards engineering practices data. ASABE, St. Joseph, pp 670–672Google Scholar
  4. Baker CGJ, McKenzie KA (2005) Energy consumption of industrial spray dryers. Dry Technol 23(1–2 SPEC. ISS):365–386CrossRefGoogle Scholar
  5. Bena B, Fuller RJ (2002) Natural convection solar dryer with biomass back-up heater. Sol Energy 72(1):75–83CrossRefGoogle Scholar
  6. Carrín ME, Crapiste GH (2008) Convective drying of foods. In: Ratti C (ed) Advances in food dehydration. CRC Press, Boca Raton, pp 123–151CrossRefGoogle Scholar
  7. Chakraborty I, Chaurasiya AK, Saha J (2010) Litchi delicacies—Few value added items par excellence. Acta Horticult (ISHS) 863:637–644Google Scholar
  8. Chua KJ, Chou SK (2003) Low-cost drying methods for developing countries. Trends Food Sci Technol 14(12):519–528CrossRefGoogle Scholar
  9. Chua KJ, Mujumdar AS, Chou SK, Hawlader MNA, Ho JC (2000) Convective drying of banana, guava and potato pieces: effect of cyclical variations of air temperature on drying kinetics and color change. Dry Technol 18(4–5):907–936CrossRefGoogle Scholar
  10. Crapiste GH, Rotstein E (1997) Design and performance evaluation of dryers. In: Valentas KJ, Rotstein E, Singh RP (eds) Handbook of food engineering practice. CRC Press, Boca Raton, pp 121–162Google Scholar
  11. Cronje RB (2008) Effect of fruit development, maturity and harvesting of litchi (Litchi chinensis Sonn.) on postharvest fruit quality. Stewart Postharvest Rev 4(3):1–10CrossRefGoogle Scholar
  12. Das S, Das T, Srinivasa Rao P, Jain RK (2001) Development of an air recirculating tray dryer for high moisture biological materials. J Food Eng 50(4):223–227CrossRefGoogle Scholar
  13. Delang CO (2002) Deforestation in northern Thailand: the result of Hmong farming practices or Thai development strategies? Soc Nat Resour 15(6):483–501CrossRefGoogle Scholar
  14. Driscoll R (2008) Food dehydration. In: Smith JS, Hui YH (eds) Food processing: principles and applications. Blackwell Publishing, Ames, pp 31–44Google Scholar
  15. Grabowski S, Marcotte M, Ramaswamy H (2003) Drying of fruits, vegetables, and spices. In: Chakraverty A, Mujumdar AS, Raghavan GSV, Ramaswamy HS (eds) Handbook of postharvest technology: cereals, fruits, vegetables, tea, and spices. Marcel Dekker, New York, pp 653–695CrossRefGoogle Scholar
  16. Holdsworth SD (1971) Dehydration of food products: a review. Int J Food Sci Technol 6(4):331–370CrossRefGoogle Scholar
  17. Huang X, Subhadrabandhu S, Mitra S, Ben-Aire R, Stern R (2005) Origin, history, production and processing. In: Menzel C, Maite G (eds) Litchi and longan: botany, production and uses. CABI Publishing, Wallingford, pp 1–24CrossRefGoogle Scholar
  18. Janjai S, Lamlert N, Tohsing K, Mahayothee B, Bala BK, Müller J (2010) Measurement and modeling of moisture sorption isotherm of litchi (Litchi chinensis Sonn.). Int J Food Prop 13(2):251–260CrossRefGoogle Scholar
  19. Jayaraman K, Gupta DD (2007) Drying of fruits and vegetables. In: Mujundar AS (ed) Handbook of industrial drying, 3rd edn. Taylor & Francis, Boca Raton, pp 606–633Google Scholar
  20. Kemp IC (2012) Modern drying technology: energy savings. In: Tsotsas E, Mujumdar AS (eds) Volume 4: energy savings, vol 4, Modern drying technology. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, pp 1–45CrossRefGoogle Scholar
  21. Kudra T (2009) Energy aspect in food dehydration. In: Ratti C (ed) Advances in food dehydration. Contemporary food engineering. CRC Press, Boca Raton, pp 423–445Google Scholar
  22. Kuhn G (1962) Dehydration studies of lychee fruit. Fla Agric Exp Station J Ser 1581:273–277Google Scholar
  23. Martinov M, Öztekin S, Mülller J (2007) Drying. In: Öztekin S, Martinov M (eds) Medicinal and aromatic crops: harvesting, drying, and processing. Haworth Food & Agricultural Products Press, Binghamton, pp 85–129Google Scholar
  24. Menzel CM (1984) The pattern and control of reproductive development in lychee: a review. Sci Hortic 22(4):333–345CrossRefGoogle Scholar
  25. Mitra SK, Pathak PK (2010) Litchi production in the Asia-Pacific region. Acta Horticult (ISHS) 863:29–36Google Scholar
  26. Moran MJ (1999) Engineering thermodynamics: combustion. In: Kreith F (ed) CRC handbook of thermal engineering, Handbook series for mechanical engineering. CRC Press, Boca Raton, pp 57–67Google Scholar
  27. Müller J, Mühlbauer W (2011) Solar drying. In: Tsotsas E, Mujumdar AS (eds) Modern drying technology, vol volume 4: energy savings, vol 4, Modern drying technology. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, pp 199–243Google Scholar
  28. Nagle M, González-Azcárraga JC, Phupaichitkun S, Mahayothee B, Haewsungcharern M, Janjai S, Leis H, Müller J (2008) Effects of operating practices on performance of a fixed-bed convection dryer and quality of dried longan. Int J Food Sci Technol 43(11):1979–1987CrossRefGoogle Scholar
  29. Nagle M, González Azcárraga JC, Mahayothee B, Haewsungcharern M, Janjai S, Müller J (2010) Improved quality and energy performance of a fixed-bed longan dryer by thermodynamic modifications. J Food Eng 99(3):392–399CrossRefGoogle Scholar
  30. Nakasone HY, Paull RE (1998) Tropical fruits. In: Crop production science in horticulture, vol 7. CABI Publishing, Wallingford, pp 173–207Google Scholar
  31. Orsat V, Vijaya Raghavan GS, Sosle V (2008) Adapting drying technologies for agri-food market development in India. Dry Technol 26(11):1355–1361CrossRefGoogle Scholar
  32. Patil RT, Shukla BD (1988) Natural convection cabinet tray dryer using agricultural waste fuel. Dry Technol 6(2):195–212CrossRefGoogle Scholar
  33. Picard A, Davis RS, Gläser M, Fujii K (2008) Revised formula for the density of moist air (CIPM-2007). Metrologia 45(2):149–155CrossRefGoogle Scholar
  34. Precoppe M, Nagle M, Janjai S, Mahayothee B, Müller J (2011) Analysis of dryer performance for the improvement of small-scale litchi processing. Int J Food Sci Technol 46(3):561–569CrossRefGoogle Scholar
  35. Raoult-Wack A, Bricas N (2002) Sustainability of food sector development in tropical areas. In: Welti-Chanes J, Barbosa-Cánovas GV, Aguilera JM (eds) Engineering and food for the 21st century. Food preservation technology. CRC Press, Boca Raton, pp 40–55Google Scholar
  36. Ratti C, Mujumdar AS (2004) Drying of fruits. In: Barrett DM, Somogyi LP, Ramaswamy HS (eds) Processing fruits. Science and technology, 2nd edn. CRC Press, Boca Raton, pp 125–157Google Scholar
  37. Rizvi SSH (2005) Thermodynamic properties of foods in dehydration. In: Rao MA, Rizvi SSH, Datta AK (eds) Engineering properties of foods. Food science and technology, 3rd edn. CRC Press, Boca Raton, pp 39–126Google Scholar
  38. Schreinemachers P, Potchanasin C, Berger T, Roygrong S (2010) Agent-based modeling for ex ante assessment of tree crop innovations: litchis in northern Thailand. Agric Econ 41(6):519–536CrossRefGoogle Scholar
  39. Sidle RC, Ziegler AD, Negishi JN, Nik AR, Siew R, Turkelboom F (2006) Erosion processes in steep terrain—truths, myths, and uncertainties related to forest management in southeast Asia. For Ecol Manag 224(1–2):199–225CrossRefGoogle Scholar
  40. Singh KK (1994) Development of a small capacity dryer for vegetables. J Food Eng 21(1):19–30CrossRefGoogle Scholar
  41. Small E (2011) Lychee, longan, and rambutan. In: Top 100 exotic food plants. CRC Press, Boca Raton, pp 361–372CrossRefGoogle Scholar
  42. Sokhansanj S, Jayas DS (2007) Drying of foodstuffs. In: Mujundar AS (ed) Handbook of industrial drying, 3rd edn. Taylor & Francis, Boca Raton, pp 522–546Google Scholar
  43. Sruamsiri P, Neidhart S (2007) Sustainable fruit production and processing systems: introduction. In: Heidhues F, Herrmann L, Neef A et al (eds) Sustainable land Use in mountainous regions of Southeast Asia. Environmental Science and Engineering. Springer, Berlin, pp 83–91CrossRefGoogle Scholar
  44. Subhadrabandhu S (1992) Status of the tropical fruit industry in Thailand. Acta Horticult (ISHS) 292:13–24Google Scholar
  45. Subhadrabandhu S, Stern RA (2005) Taxonomy, botany and plant development. In: Menzel CM, Waite GK (eds) Litchi and longan: botany, production and uses. CABI Publishing, Wallingford, pp 25–34CrossRefGoogle Scholar
  46. Subhadrabandhu S, Yapwattanaphun C (2001) Lychee and longan production in Thailand. Acta Horticult (ISHS) 558:49–57Google Scholar
  47. Tindall HD (1994) Sapindaceous fruits: botany and horticulture. In: Janick J (ed) Horticultural reviews, vol 16. John Wiley & Sons, Inc, New York, pp 143–196Google Scholar
  48. Tippayawong N, Tantakitti C, Thavornun S (2008) Energy efficiency improvements in longan drying practice. Energy 33(7):1137–1143CrossRefGoogle Scholar
  49. Tippayawong N, Tantakitti C, Thavornun S, Peerawanitkul V (2009) Energy conservation in drying of peeled longan by forced convection and hot air recirculation. Biosyst Eng 104(2):199–204CrossRefGoogle Scholar
  50. WMO (2008) Guide to meteorological instruments and methods of observation, vol 8. WMO-No. 8, 7th edn. World Meteorological Organization (WMO), GenevaGoogle Scholar
  51. Xiao C (2009) Drying and dried food quality. In: Ortega-Rivas E (ed) Processing effects on safety and quality of foods. Contemporary food engineering. CRC Press, Boca Raton, pp 323–340Google Scholar
  52. Zhao H, Li C, Guan Z (1999) Experimental research on drying characteristics of litchi. Dry Technol 17(9):1915–1925Google Scholar

Copyright information

© Association of Food Scientists & Technologists (India) 2014

Authors and Affiliations

  • Marcelo Precoppe
    • 1
    Email author
  • Serm Janjai
    • 2
  • Busarakorn Mahayothee
    • 3
  • Joachim Müller
    • 1
  1. 1.Institute of Agricultural EngineeringUniversität HohenheimStuttgartGermany
  2. 2.Department of PhysicsSilpakorn UniversityNakhon PathomThailand
  3. 3.Department of Food TechnologySilpakorn UniversityNakhon PathomThailand

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