State of water in starch-water systems in the gelatinization temperature range as investigated using dielectric relaxation spectroscopy

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Abstract

The dielectric response of native wheat starch-water slurries containing 5-60% starch (w/w) was measured in the frequency range of 0.2-20 GHz after heating the slurries to 7 different temperatures between 25 and 90 °C for 30 min. Three relaxations, with relaxation time range of 4-9 ps, 20-25 ps and 230-620 ps at 25 °C, were identified from the dielectric spectra of starch slurries. The fastest relaxation process (4-9 ps) was attributed to bulk water while the two slower relaxations were attributed to the confined water molecules present in the starch-water system. The amount of water exhibiting the slowest relaxation (230-620 ps) was calculated to be 0.08-0.16 g water/g starch, which was close to the monolayer water associated with wheat starch. Mobility of bulk water was significantly reduced (P < 0.001) upon gelatinization at low starch concentration (10% starch), but remained unaffected at higher starch concentrations. The mobility of two slower relaxing water species was not significantly influenced (P > 0.19) by gelatinization at all starch concentrations.

Original languageEnglish (US)
Pages (from-to)24-31
Number of pages8
JournalCarbohydrate Polymers
Volume87
Issue number1
DOIs
StatePublished - Jan 4 2012

All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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