Porous frozen material approach to freeze-drying of instant coffee

Wei Wang, Shihao Wang, Yanqiu Pan, Jing Yang, Shuo Zhang, Guohua Chen

Research output: Journal article publicationJournal articleAcademic researchpeer-review

4 Citations (Scopus)

Abstract

Porous frozen material with a certain initial porosity was prepared to explore its influence on freeze-drying experimentally. Soluble coffee was selected as the solute in aqueous solution and liquid nitrogen ice-cream making method was used to prepare the frozen materials. Results showed that freeze-drying can be significantly enhanced using the initially porous frozen material compared with the traditionally solid one. By keeping the same sample mass and moisture content with sole radiation heating, drying time of the porous frozen sample was about one third shorter than that of the solid one under the same tested operating conditions. SEM images of dried products revealed that the porous material had a loose and tenuous structure that was favorable to the transportation of sublimated vapor and the desorption of bound moisture. Appropriately increasing the chamber surface temperature benefited the freeze-drying process and changing the chamber pressure had little effect on the process. Combined radiation and conduction heating can further promote the freeze-drying process and save as much as 36.4% of the drying time. The porous frozen material was found to have a wider range of operating temperature and result in relatively lower residual moisture content.

Original languageEnglish
Pages (from-to)2126-2136
Number of pages11
JournalDrying Technology
Volume37
Issue number16
DOIs
Publication statusPublished - 10 Dec 2019

Keywords

  • desorption
  • drying time
  • Freeze-drying
  • initial saturation
  • sublimation

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Physical and Theoretical Chemistry

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