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- Author or Editor: T. Belopolskaya x
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Abstract
DSC study of native and denatured biopolymers with different chemical and steric structure was carried out in a wide range of temperatures and water contents. It was shown that all the native and denatured humid biopolymers studied are glassy systems. The residues of native structures surviving after partial dehydration prevent the glass transition at the glass transition temperatures of the denatured biopolymers. In dehydrated native biopolymers the processes of melting and glass transition take place in the same temperature range that leads to a large change of the heat capacity across denaturation.
Abstract
By method of differential scanning calorimetry the absolute values of heat capacity for the systemwater–biopolymer (globular and fibrillar proteins and DNA) were measured in a wide range of temperatures (from -30 up to 130°C) and concentrations of proteins both in native and denatured states. Thermal properties of humid denatured biopolymers demonstrate a characteristic anomaly in the form of the heat capacity jump at temperature depending on the bound water content. It has been shown that in the systems studied a glass transition, where water serves as a native plasticizer, is observed. It has been established that the S-shaped character of all heat capacity curves obtained on dehydration for native and denatured biopolymers is due to the gradual transition to the glassy state of both native and denatured samples. It was found that thermally denatured humid small globular proteins at subsequent dissolving in water at room temperature are able to restore their native structure.
Abstract
DSC studies of melting process of annealed native structures and postdenatured ones in low-amylose starches with different degrees of hydration were carried out. The starch recrystallization at different thermal treatments of the samples was studied both after the complete and partial destroy of native structures. It has been shown that native structures as well as postdenatured ones possess the ability to perfection, which is most clearly seen at the annealing at temperatures inside their melting ranges. The results obtained demonstrate that at the same duration of annealing the process of crystal perfection for secondary starch structures proceed more intensively compared to the native ones. The presence of the remained native structures in partial melt in contrast to the remained gel ones restricts the ability of the recrystallized structures to perfection.