Structural Transformations during Gelatinization of Starches in Limited Water:  Combined Wide- and Small-Angle X-ray Scattering Study

• Published in: Biomacromolecules Vol. 7; no. 4; pp. 1231 - 1238
• Main Authors: Vermeylen, Rudi, Derycke, Veerle, Delcour, Jan A, Goderis, Bart, Reynaers, Harry, Koch, Michel H. J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.04.2006
• Subjects: Applied sciences; Biological and medical sciences; Chemical Phenomena; Chemistry, Physical; Crystallization; Exact sciences and technology; Food industries; Fundamental and applied biological sciences. Psychology; Gels - chemistry; Natural polymers; Physicochemistry of polymers; Scattering, Radiation; Sensitivity and Specificity; Starch - chemistry; Starch and polysaccharides; Starch and starchy product industries; Surface Properties; Temperature; Water - chemistry; X-Ray Diffraction; Lamellar structure; Nematic smectic transformation; Rice flour; Supramolecular structure; Potato starch; Temperature effect; Oside polymer; Structure modification; Small angle X ray scattering; Experimental study; Gelatinization
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm050651t

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.