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 (σ_oc, σ_h) increased with the increase in OSA content and the decrease in temperature. Over the temperature range of 10-50°C, the effect of temperature on apparent viscosity (η_{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 (η?*) and steady shear (η_a) viscosities of OSA starch pastes at various OSA contents did not follow the Cox-Merz super-position rule.