Abstract:In order to improve the physical properties of rice starch (RS) and expand its application fields, analytical techniques such as rheological analysis, scanning electron microscopy (SEM), low-field nuclear magnetic resonance (LF-NMR), and X-ray diffraction (XRD) were used to systematically study the influence of curdlan (CL) addition amount on the structure and properties of the thermally irreversible gel of the CL - RS blends. It was found that when the CL addition amount reached the threshold of 0.60%, compared with the control, the gelatinization temperature was decreased by 1.69 °C, the retrogradation viscosity was increased by 25.00%, the syneresis rate was reduced by 47.73%, and the transverse relaxation time T22 was shortened by 58.01% to 6.45 ms. Compared with the group with 0.40% CL addition, the peak value of the storage modulus was increased by 40.20%, the G' value at the end of cooling was increased by 21.46%, and the chewiness was improved by 24.76%. When the CL addition amount was ≤ 0.60%, the retrogradation viscosity, the viscoelastic modulus at each phase-change temperature node, the chewiness, and the ratio of the bound-water peak area (A21) were increased significantly with the increase of the CL addition amount, while the transverse relaxation times T22 and T23 of water molecules, and the gel syneresis rate were decreased. Meanwhile, the porosity of the microstructure was decreased and the distribution uniformity was improved. When the CL addition was exceeded the threshold (0.80%), a reduction of 11.37% in G' at the end of cooling and a 42.89% decrease in chewiness were observed, accompanied by a transformation of the microstructure from a porous network to a dense layered structure.The mechanism was attributed to CL-induced enhancement of hydrogen-bond crosslinking density, which facilitated the formation of stable three-dimensional RS networks.In conclusion, the properties of the RS-based blend gel were effectively regulated by the threshold effect of CL addition amount, and a theoretical reference was provided for the development of new RS-based heterogeneous polysaccharide blend system foods.
