Gelatinization of starch in excess water: beyond the melting of lamellar crystallites. A combined wide- and small-angle X-ray scattering study.
The gelatinization of waxy rice, regular rice, and potato starch suspensions (66% w/w moisture) was investigated by real-time small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) during heating and by fast ramp differential scanning calorimetry (DSC). The high-angle tail of the SAXS patterns suggested the transition from surface to mass fractal structures in the DSC gelatinization range. Amylose plays a major role in determining the dimensions of the self-similar structures that develop during this process as the characteristic power-law scattering behavior extends to lower scattering angles for regular than for waxy starches. Crystallinity of A-type starches is lost in the temperature region roughly corresponding to the DSC gelatinization range. At the end of the gelatinization endotherm, the B-type potato starch showed residual crystallinity (WAXD), while SAXS-patterns exhibited features of remaining lamellar stacks. Results indicate that the melting of amylopectin crystallites during gelatinization is accompanied by the (exothermic) formation of amorphous networks.
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
D000688:Amylose / Q000737:chemistry; D001672:Biocompatible Materials / Q000737:chemistry*; D001709:Biotechnology / Q000379:methods; D002152:Calorimetry, Differential Scanning / Q000379:methods; D002627:Chemistry, Physical / Q000379:methods; D003460:Crystallization; D005780:Gelatin / Q000737:chemistry*; D046911:Macromolecular Substances; D015233:Models, Statistical; D012275:Oryza; D012542:Scattering, Radiation; D013213:Starch / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry; D014965:X-Rays
D001672:Biocompatible Materials; D046911:Macromolecular Substances; D014867:Water; D005780:Gelatin; D013213:Starch; D000688:Amylose