Water dynamics in whey-protein-based composite hydrogels by means of nmr relaxometry

Abstract

Whey-protein-isolate-based composite hydrogels with encapsulated black carrot (Daucus carota) extract were prepared by heat-induced gelation. The hydrogels were blended with gum trag-acanth, pectin and xanthan gum polysaccharides for modulating their properties.1H spin-lattice relaxation experiments were performed in a broad frequency range, from 4 kHz to 30 MHz, to obtain insight into the influence of the different polysaccharides and of the presence of black carrot on dynamical properties of water molecules in the hydrogel network. The1H spin-lattice relaxation data were decomposed into relaxation contributions associated with confined and free water frac-tions. The population of the confined water fraction and the value of the translation diffusion coef-ficient of water molecules in the vicinity of the macromolecular network were quantitatively determined on the basis of the relaxation data. Moreover, it was demonstrated that the translation diffusion is highly anisotropic (two-dimensional, 2D). © 2021 by the authors. Licensee MDPI, Basel, Switzerland.