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Phase transitions of the starch–water system
Author(s) -
Donovan John W.
Publication year - 1979
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1979.360180204
Subject(s) - endotherm , chemistry , endothermic process , differential scanning calorimetry , starch , stoichiometry , crystallite , melting point , analytical chemistry (journal) , phase (matter) , melting temperature , crystallography , thermodynamics , chromatography , organic chemistry , materials science , physics , adsorption , composite material
Abstract When purified potato starch granules are heated in the presence of limited amounts of water (less than 1.5 H 2 O: starch, w/w), two endothermic transitions are observed by differential scanning calorimetry. The lower temperature endotherm is always observed at a fixed temperature, 66°C; it is the only endotherm observed when excess water is present. The higher temperature endotherm is observed at increasing temperatures as the water content is decreased. The size of this endotherm decreases with water content. The appearance of the higher temperature endotherm allows the determination of the stoichiometry for full hydration of starch, 14 H 2 O/hexose unit. The shift of the higher temperature endotherm is interpreted as the lowering of the melting point of starch crystallites by solvent water.