Effect of octenylsuccinylation on rheological properties of corn starch pastes

Rheological properties of corn starch octenylsuccinate (OSA starch) pastes (5%, w/w), at different 1-octenylsuccinic anhydride (OSA) contents (0, 1.0, 1.5, 2.0 and 2.5%, w/w) were evaluated in steady and dynamic shear. The OSA starch pastes had high shear-thinning behaviors and their flow behaviors were described by power law, Casson, and Herschel-Bulkley models. Magnitudes of consistency index (K, K-h) and yield stress (sigma(oc), sigma(h)) increased with the increase in OSA content and the decrease in temperature. Over the temperature range of 10-50degreesC, the effect of temperature on apparent viscosity (eta(a,100)) was described by the Arrhenius equation. The activation energy values (E-a = 10.7-13.9 kJ/mol) of OSA starches were lower than that (E-a = 15.9 kJ/mol) of native starch. Dynamic frequency sweep test showed that both storage modulus (G) and loss modulus (G") of OSA starch pastes increased with the increase in OSA content. Dynamic (eta(star)) and steady shear (eta(a)) viscosities of OSA starch pastes at various OSA contents did not follow the Cox-Merz super-position rule.