Pasting, thermal, and rheological properties of rice starch partially replaced by inulin with different degrees of polymerization

Abstract

Abstract: Blending with non-starch hydrocolloids is a crucial method to modify the processing properties of native starch. However, few comprehensive studies investigated the effects of inulin on the properties of rice starch (RS). In this research, we used three types of inulin with different degrees of polymerization (DP), namely, short-chain inulin (SI, DP 10), and long-chain inulin (LI, DP > 23), to investigate the effects of inulin on the pasting, thermal, and rheological properties of RS and to provide the foundation for the application of inulin in RS-based food. Inulin addition increased the pasting temperature of RS and decreased all viscosity indices, including the peak, final, breakdown, and Setback viscosities of RS. Compared with LI, SI and MI exerted stronger influence on the viscosity indices of RS. The gelatinization temperature levels of the RS–inulin blends were higher than that of starch alone. The RS and RS–inulin blends exhibited a shear-thinning property, and stress–shear hysteresis loops were observed during shear. Thixotropy followed the order RS > RS-LI > RS-MI > RS-SI. Dynamic viscoelasticity results indicated that the RS and RS–inulin blends displayed weak gel-like behavior. Replacement of RS with LI and MI evidently increased the elastic properties more than the viscous properties of the RS–inulin blends.