Effect of various gums on flow properties and yield stress of Korean sweet potato starch

The effects of seven commercial gums (xanthan gum, guar gum, pectin, gum arabic, gellan, locust bean gum, and sodium alginate) at different concentrations (0, 0.3, and 0.6%) on flow properties of sweet potato starch (SPS) pastes were investigated. Flow behavior characteristics were adequately described by power law flow model, and yield stress was also measured by vane method. SPS-gum mixtures (5% w/w) at 25°C were found to have high shear-thinning flow behavior with yield stress, and their consistency index (K) and apparent viscosity (η_a,100) increased with elevated gum concentration, except for pectin and sodium alginate. Vane yield stress (σ_o) value of SPS-pectin mixture was lower when compared to other mixtures while that of SPS-gellan mixture was much higher. Most of the gums, except for pectin, gum arabic, and sodium alginate, showed a synergistic effect on the elastic properties of SPS-gum mixtures. In general, the flow properties of SPS-gum mixtures appeared to be strongly influenced by the addition of gum, and dependent on the type and concentration of gum.