Rheological Properties of Sago Starch

Abstract

The swelling characteristics and rheological properties of 11 sago starches have been studied and compared to a number of commonly used starches. The swelling power of the sago starches were all very similar except for two samples which were known to contain a lower molecular mass amylose component. The swelling and solubility for these two samples were higher than the rest. The values for sago starches were similar to that for potato and tapioca starch, but higher than maize and pea starch. The storage modulus, G‘, of the sago starches as studied by small deformation oscillation measurements showed a rapid initial increase in G‘ followed by the development of a pseudoplateau. The dependence of G‘ on the molecular mass of the amylose followed the relationship G‘ ∝ M-0.4. Gels were formed only at sago starch concentrations of >3.5%, corresponding to an amylose concentration of ∼ 1.0% and varied with concentration according to the relationship G‘ ∝ C1.8 and G‘ ∝ C2.5 for high and low amylose molecular mass samples, respectively. Gel strength (GS) measurements also confirmed that the minimum concentration for gelation was ∼3.5% and that GS ∝ C2.0. Sago starches showed good freeze−thaw stability compared to other starch types. Keywords: Sago starch; swelling; solubility; gelatinization; gelation; rheology; freeze−thaw stability