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Objectives And Learning Outcomes

  1. 1.

    Review the theory of freeze drying.

     
  2. 2.

    Examine the critical requirements for successful freeze drying.

     
  3. 3.

    Calculate the diffusion coefficient and mass transfer coefficient.

     
  4. 4.

    Determine and compare the physical and mechanical properties of the freeze-dried products with those of the heated air-dried products.

     

Introduction

Freeze drying is a method of water removal from a frozen product mainly by sublimation. The frozen water, ice, changes directly to the gas phase without passing through the liquid phase. Sublimation is only possible under the conditions below the triple point of water (temperature 0.01°C; pressure 610.5 Pa) at which all three phases of water are in equilibrium (Figure 12.1). Any material must be adequately pre-frozen before starting the freeze drying process. A maximum amount of ice is obtained when material is frozen at temperatures between the glass transition temperature of maximally freeze concentrated material ( T g )...

Keywords

Mass Transfer Coefficient Food Material Evaporative Cool Product Temperature Unfrozen Water 
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.

References

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Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  • Lea Hyvönen
    • 1
  • Kirsi Jouppila
    • 1
  1. 1.Department of Food TechnologyUniversity of HelsinkiP.o. Box 66Finland

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