N.E. Kochkina, V.A. Padokhin, O.А. Skobeleva, N.R. Andreev, N.D. Lukin
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Summary. Characteristics of starch gelatinized by mechanothermal method in a rotor-pulse device (RPD) under shear rates varied from 1,3∙104 to 5,5∙104 s-1 were studied by dynamic light scattering and UV-Vis spectrophotometry. Starch solutions (0,5 g/l, solvent – dimethylsulfoxide) prepared from the films formed by drying of starch gels were used for determination of hydrodynamic radius distribution of biopolymer macromolecules. Native corn starch that is consisted of two polysaccharides (amylose and amylopectin) was characterized by bimodal size distribution of macromolecules, with the modes corresponding to 25 and 175 nm hydrodynamic radii (RH). After gelatinization of starch in RPD at shear rate 1,3∙104 s-1 the sizes of polysaccharide macromolecules didn't change. At the same time there exists a threshold shear rate value (3.2•104 с-1) above which mechanothermal gelatinization of starch is accompanied by its destruction. In this case starch was characterized by monomodal size distribution of macromolecules with RH 85 nm. Analysis of the starch-iodine complexes spectra revealed that the positions of the absorption maxima for starch gelatinized in RPD and native starch were the same. It was supposed that degradation of starch polysaccharides (amylose and amylopectin) after mechanothermal gelatinization was equal.
Keywords: nanobiocomposites, starch, gelatinization, rotary-impulse device, dynamic light scattering.