Correlated changes in structure and viscosity during gelatinization and gelation of tapioca starch granules
Journal
IUCrJ
Journal Volume
1
Journal Volume
1
Pages
418-428
Start Page
418
End Page
428
ISSN
20522525
Date Issued
2014-10-10
Author(s)
Huang, Hsien-Kai
Sheu, Hwo-Shuenn
Chuang, Wei-Tsung
Jeng, U-Ser
Su, An-Chung
Wu, Wei-Ru
Liao, Kuei-Fen
Chen, Chun-Yu
Chang, Shing-Yun
Abstract
Melting of native tapioca starch granules in aqueous pastes upon heating is observed in situ using simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) and solution viscometry. Correlated structure and viscosity changes suggest closely associated amylose and amylopectin chains in the semicrystalline layers, and the release of amylose chains for enhanced solution viscosity occurs largely after melting of the semicrystalline structure. Before melting, WAXS results reveal mixed crystals of A- and B-types (∼4:1 by weight), whereas SAXS results indicate that the semicrystalline layers are composed of lamellar blocklets of ca 43 nm domain size, with polydisperse crystalline (≃7.5 nm) and amorphous (≃1.1 nm) layers alternatively assembled into a lamellar spacing of ≃8.6 nm with 20% polydispersity. Upon melting, the semicrystalline lamellae disintegrate into disperse and molten amylopectin nanoclusters with dissolved and partially untangled amylose chains in the aqueous matrix which leads to increased solution viscosity. During subsequent cooling, gelation starts at around 347 K; successively increased solution viscosity coincides with the development of nanocluster aggregation to a fractal dimension ≃2.3 at 303 K, signifying increasing intercluster association through collapsed amylose chains owing to decreased solvency of the aqueous medium with decreasing temperature.
Subjects
gelatinization
gelation
SAXS/WAXS
tapioca starch granules
viscosity
Publisher
International Union of Crystallography
Type
journal article