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Rheological Studies on Potato Starch Pastes at Low Concentrations. Part IV: Absolute Measurements of the Rheological Properties of Starch During Gelatinization
Author(s) -
Janas Piotr
Publication year - 1991
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.19910430504
Subject(s) - rheology , shear thinning , starch , viscoplasticity , materials science , starch gelatinization , thermodynamics , chemistry , composite material , constitutive equation , organic chemistry , physics , finite element method
The method of absolute measurement of the rheological properties of starch suspensions during gelatinization is presented. It enables to determine the flow curves already in the early stage of the process. The studies were carried out on 1.5% aqueous suspension of potato starch. They have shown that just at the temperature of approximately 15°C above the beginning of gelatinization the formed paste starts to behave as a shear‐thinning liquid with the yield stress, τ y. The non‐ Newton ian effects increase as the temperature increases. Experimental data are satisfactorily described by the modified four‐parameter power law: τ = τ y + τ 0 (γ˙/γ˙ 0 ) n . The temperature dependences of n‐ and τ y ‐parameters univocally determine the evolution of rheological properties which are observed on experiment. This evolution is understood as the transformation of Newton ian liquid through a pseudoplastic liquid into a nonlinear viscoplastic one.