Physical investigations of surface membrane-water relationship of intact and gelatinized wheat-starch systems

Albert Linton Charles, Hsien Ming Kao, Tzou Chi Huang

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28 Scopus citations

Abstract

Water mobility in intact and dried gelatinized starch was investigated by gravimetric water sorption, scanning electron microscopy (SEM), and solid-state nuclear magnetic resonance (NMR). A multi-component exponential model quantitatively measured different spin-spin relaxation times of two water components, namely bound water (Tsi) at 3.16 ms and mobile or free water (Tsii) at 3.23 ms, as a function of water activity (a w). The starch samples were moistened to 30% moisture content. SEM confirmed the disrupted, absorbent microstructure in dried, gelatinized starch powder and revealed starch granules in an incomplete gelatinized state, as compared to the complete membrane surface of the intact starch granule. Starch granules sorbed significantly differently at low aw, but after a w=0.44, sorption leveled similarly with increasing aw. The presence and role of a surface membrane was concluded, in support of the hypothetical "water sink" properties of intact granules, and was considered to influence in part the sorption behavior of incompletely gelatinized starch granules.

Original languageEnglish
Pages (from-to)2403-2408
Number of pages6
JournalCarbohydrate Research
Volume338
Issue number22
DOIs
StatePublished - 31 Oct 2003

Keywords

  • NMR spectroscopy
  • SEM
  • Starch
  • Surface membrane
  • Water activity

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