Structural transformations during gelatinization of starches in limited water: combined wide- and small-angle X-ray scattering study.
Rice flour (18-25% moisture) and potato starch (20% moisture) were heated with continuous recording of the X-ray scattering during gelatinization. Rice flours displayed A-type crystallinity, which gradually decreased during gelatinization. The development of the characteristic 9 nm small-angle X-ray scattering (SAXS) peak during heating at sub-gelatinization temperatures indicated the gradual evolution into a stacked lamellar system. At higher temperatures, the crystalline and lamellar order was progressively lost. For potato starch (B-type crystallinity), no 9 nm SAXS peak was observed at ambient temperatures. Following the development of lamellar structures at sub-gelatinization temperatures, B-type crystallinity and lamellar order was lost during gelatinization. On cooling of partially gelatinized potato starch, A-type crystallinity steadily increased, but no formation of stacked lamellar structures was observed. Results were interpreted in terms of a high-temperature B- to A-type recrystallization, in which the lateral movement of double helices was accompanied by a shift along their helical axis. The latter is responsible for the inherent frustration of the lamellar stacks.
Vermeylen
Rudi
R
Laboratory of Food Chemistry, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium. rudi.vermeylen@scarlet.be
Derycke
Veerle
V
Delcour
Jan A
JA
Goderis
Bart
B
Reynaers
Harry
H
Koch
Michel H J
MH
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D005782:Gels / Q000737:chemistry; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D013213:Starch / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
D005782:Gels; D014867:Water; D013213:Starch