Phase separation in amorphous hydrophobically modified starch–sucrose blends: Glass transition, matrix dynamics and phase behavior

David J. Hughes, Gabriela Badolato Bönisch, Thomas Zwick, Christian Schäfer, Concetta Tedeschi, Bruno Leuenberger, Francesca Martini, Giacomo Mencarini, Marco Geppi, M. Ashraf Alam, Job Ubbink*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

11 Citations (Scopus)

Abstract

The phase behavior and matrix dynamics of amorphous blends of octenyl succinic anhydride (OSA) modified starch and sucrose was studied as function of blend composition and water content. Phase separation into two amorphous phases, one enriched in OSA starch and the other in sucrose, was confirmed by differential scanning calorimetry (DSC). DSC and 1H solid-state NMR show that the phase separation is only partial. The glass transition temperature (Tg) of the OSA starch-rich phase was found to be ∼30–100 K higher than the Tg of the sucrose-rich phase, depending on blend composition and water content. A novel type of coupling between changes in physical state of the sucrose-rich phase and plasticizer redistribution is proposed, leading to an unexpected increase of the glass transition temperature of the modified starch-rich phase at higher matrix water contents. A quantitative model for the phase separation of the anhydrous blends into two amorphous phases is presented. The model predicts that, with increasing blend sucrose content, the weight fraction of the sucrose-rich phase decreases, while the sucrose content of both the OSA starch-rich phase and the sucrose-rich phase increases. This novel phenomenon is relevant in the understanding of the stability and performance of multiphase food and pharmaceutical components.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalCarbohydrate Polymers
Volume199
Early online date18 Jun 2018
DOIs
Publication statusPublished - 1 Nov 2018

Keywords

  • Amorphous phase separation
  • Differential scanning calorimetry
  • Glass transition
  • OSA starch
  • Solid-state NMR
  • Sucrose

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