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The Retrogradation of Concentrated Wheat Starch Systems
Author(s) -
Lionetto Francesca,
Maffezzoli Alfonso,
Ottenhof MarieAstrid,
Farhat Imad A.,
Mitchell John R.
Publication year - 2005
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.200400298
Subject(s) - crystallinity , amylopectin , differential scanning calorimetry , dynamic mechanical analysis , retrogradation (starch) , materials science , thermal analysis , amorphous solid , relaxometry , chemical engineering , starch , analytical chemistry (journal) , crystallography , chemistry , polymer , thermodynamics , composite material , amylose , thermal , organic chemistry , medicine , physics , spin echo , radiology , magnetic resonance imaging , engineering
The ageing of non‐expanded wheat starch extrudates containing 37% and 51% water on a dry solids basis (d.s.b.) at 25°C was studied using Differential Scanning Calorimetry (DSC), Wide Angle X‐ray Diffraction (XRD), proton Nuclear Magnetic Resonance (NMR) relaxometry and Dynamic Mechanical Thermal Analysis (DMTA). The retrogradation rate increased with water content (∼0.02 h −1 at 37% water (d.s.b.) compared to ∼0.06 h −1 at 51%). While a good correlation was found between the DSC, XRD and NMR data, the kinetics of retrogradation measured by DMTA was delayed. The findings were interpreted in terms of the different molecular processes probed by the different techniques. In addition to the kinetics, information on the physical structure of the partially crystalline retrograded materials were obtained. DSC suggested a broad bimodal melting behaviour, which was attributed to the melting of the crystalline structure followed by the dissociation of the double helices. XRD suggested that at both water contents, the recrystallisation of amylopectin led principally to the A‐polymorph. DMTA suggested a significant interaction between the amorphous and crystalline phases, with a requirement of a minimum relative crystallinity index of ∼0.8 (e.g. ∼80% of the crystallinity index of the fully retrograded material), before any increase in the elastic modulus (at 25°C) was measured.