期刊
CARBOHYDRATE POLYMERS
卷 87, 期 1, 页码 24-31出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.carbpol.2011.06.057
关键词
Starch gelatinization; Dielectric spectroscopy; Water mobility; Confined water; Bulk water
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 degrees C for 30 min. Three relaxations, with relaxation time range of 4-9 ps, 20-25 ps and 230-620 ps at 25 degrees 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. (C) 2011 Elsevier Ltd. All rights reserved.
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