Dehydration I – Tray Drying of ApplesTray Drying Of Apples

  • Margarida Vieira
  • Jorge Pereira
Part of the Integrating Safety and Environmental Knowledge Into Food Studies towards European Sustainable Development book series (ISEKI-Food, volume 5)

Objectives And Learning Outcomes

  1. 1.

    Describe the drying process for a tray drier and indicate relevant variables that are used to control the process.

  2. 2.

    Calculate the drying times for different periods of a drying process.



Dehydration is a food unit operation that is used to extend the shelf-life of a foodstuff by reducing its water activity (aw). Drying with hot air using a tray or cabinet drier is one of the methods of food dehydration. Heat transferred to the surface of a foodstuff exposed to hot air, provides the latent heat of vaporization to evaporate moisture from the food surface. Water vapor diffuses through the film of air that is formed at the food surface and is subsequently removed by the circulating air. A region of low vapor pressure thus forms at the food surface, establishing a vapor pressure gradient between the inner humid layer and the outer layer of dry air. This gradient acts as the driving force of the drying process (Geankoplis, 1993, Heldman...


Fall Rate Period Food Surface Apple Slice Critical Moisture Content Constant Rate Period 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


  1. Brennan, J.G., Butters, J.R., Cowell, N.D., and Lilley, A.E.V., 1990 Food Engineering Operations, Elsevier Applied Science, London & New York.Google Scholar
  2. Fellows, P., 2000 Food Processing Technology, Woodhead Publishing Elsevier Applied Science, Cambridge.CrossRefGoogle Scholar
  3. Geankoplis, C.J., 1993 Transport Processes and Unit Operations, 3rd Edition,Prentice-Hall International, pp: 640–696.Google Scholar
  4. Heldman, D.R. and Singh, R.F., 1981. Food Process Engineering. Second Edition. AVI Publishing, Westport, Conn.Google Scholar

Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  • Margarida Vieira
    • 1
  • Jorge Pereira
  1. 1.Universidade do Algarve, Escola Superior de Tecnologia Universidade do Algarve, Escola Superior de TecnologiaFrance

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