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Effects of Compositional and Granular Properties on the Pasting Viscosity of Rice Starch Blends
Author(s) -
Chen Jihjou,
Lai Vivian M.F.,
Lii Chengyi
Publication year - 2003
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.200390039
Subject(s) - starch , swelling , amylose , viscosity , materials science , isothermal process , shear rate , reduced viscosity , mixing (physics) , chemical engineering , composite material , chemistry , food science , thermodynamics , physics , quantum mechanics , engineering
The changes in swelling power and pasting properties of suspensions of starch blends were studied in dependence on starch composition and at various isothermal temperatures ( T iso ). Samples were prepared by mixing rice starches from Kaoshiung Sen 7 (KSS7, a high‐amylose‐content variety) and Taichung waxy 70 (TCW70, a waxy variety). Generally, mixing these starches at a comparable ratio caused significant decrements in overall swelling power, onset temperature of gelatinization or viscosity rise, and final viscosity of hot pastes after 30 min of isothermal stirring. Notable increases in the peak and conclusion temperatures of gelatinization and in the peak viscosity of the pastes were also observed. Generally, all viscosity parameters of the blends showed two linear dependencies on the starch composition, the graphs intersecting at a critical starch composition depending on the parameters concerned. The onset temperature of viscosity increase was related to the volume fraction of swollen granules when they were just closely packed in suspension. The volume fraction of KSS granules was smaller than that of TCW70. In addition, the rate of viscosity increase and the peak viscosity of the starch suspensions could be well described in terms of the swelling power ( Q ) when Q ≤ ∼27, and depending on the T iso examined. From the photomicrographs of starch suspensions, the extensive shear‐induced disintegration of TCW70 granules in the co‐existence of rigid KSS7 granules was evident and in turn responsible for the reduced final viscosities of the hot pastes obtained from starch blends.