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Behaviour of Oxidized Starches Towards Cyanoethylation
Author(s) -
ElThalouth I. Abd,
Ragheb A.,
Refai R.,
Hebeish A.
Publication year - 1990
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.19900420107
Subject(s) - thixotropy , starch , shear thinning , rheology , chemistry , viscosity , apparent viscosity , polysaccharide , nitrogen , polymer chemistry , shear rate , food science , chemical engineering , organic chemistry , materials science , composite material , engineering
Starch of different molecular sizes brought about by oxidation of maize and rice starches were cyanoethylated under identical conditions. The degree of cyanoethylation, expressed as % N, was found to depend mainly on the molecular size of starch irrespective of its kind. As the molecular size decreases the degree of cyanoethylation increases. Cyanoethyl starches are water soluble and can be precipitated by ethanol. It was also found that the rheological properties are determined by the nitrogen content of cyanoethyl starch. When the latter acquires low nitrogen content, it exhibits non‐ Newtonian pseudoplastic behaviour. On the other hand, cyanoethyl starches with higher nitrogen content are characterized by non‐ Newtonian thixotropic. At constant rate of shear, the apparent viscosity of cyanoethyl starches is directly related to its molecular size. Storing of pastes prepared from these cyanoethyl starches for 7 d exerts considerable influence on rheological properties and apparent viscosity of these derivatives.