title: The retrogradation of waxy maize starch extrudates: effects of storage temperature and water content.
abstract: The effects of water content and storage temperature on the kinetics of the retrogradation of nonexpanded waxy maize starch extrudates were studied using (1)H pulsed NMR and wide-angle X-ray diffraction. The increase in crystallinity observed by XRD was accompanied by a decrease in the relaxation times of the solid-like component of the NMR free induction and the spin-echo decays, and an increase in the contribution of the solid-like component to the total signal. The dependence of the rate of starch retrogradation on the storage temperature showed the typical "bell-shaped" behavior, which was successfully modeled using the Lauritzen-Hoffman theory of crystallization of chain-folded polymers. This theory was extended to model the effect of water content on the rate of isothermal crystallization by exploiting the ten-Brinke and Karasz, and the Flory equations to describe the dependence of the glass-transition and the melting temperatures on water content.
authors.affiliation: Division of Food Sciences School of Biological Sciences University of Nottingham Loughborough LE12 5RD UK. imad.farhat@nottingham.ac.uk
authors.forename: I A
authors.initials: IA
authors.lastname: Farhat
authors.forename: J M
authors.initials: JM
authors.lastname: Blanshard
authors.forename: J R
authors.initials: JR
authors.lastname: Mitchell
mesh_terms: D001704:Biopolymers / Q000737:chemistry; D003460:Crystallization; D005519:Food Preservation; D009682:Magnetic Resonance Spectroscopy; D013213:Starch / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000032:analysis; D014961:X-Ray Diffraction; D003313:Zea mays / Q000737:chemistry*
chemical_list: D001704:Biopolymers; D014867:Water; D013213:Starch