Temperature dependence of starch gel rheological properties

In an attempt to learn more about molecular mechanisms and thermodynamic preconditions of development of spatial structures of starch systems, the authors analyzed the kinetics of structuralization processes in the temperature function of the course of these processes. The method of dynamic-mechanical analysis (DMA) was employed in the performed investigations. On the basis of empirical values of G1 and G2, the energetic status of the gel network as well as changes in this status during the structuralization process was determined. In the state of complete hydration, the retrogradation mechanism of the examined starch systems consisted in the bundle–coil transition. This transition required a decline in the temperature of the system below temperature θ determined by the ratio of the enthalpy to entropy transition: ΔH/ΔS ≈ 322 K ≈ 49 °C. This transition is a cooperative transformation of two fragments of neighboring chains in a condition of chaotic confrontation to a state of bihelical associated molecules. The bihelical association of starch chains is the main source of stabilization of the spatial structure of starch hydrogels below the θ transition temperature.

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