Xanthan gum - mucin complexation: Molecular interactions, thermodynamics, and rheological analysis
Document Type
Article
Publication Date
5-1-2021
Abstract
Texture perception, astringency phenomena, and oral sensation are directly influenced by molecular interactions. This study systematically characterizes the diverse array of molecular interactions in a binary model system comprising of mucin, the major viscosity enhancer of biological fluids, and xanthan gum, a major food hydrocolloid, at a pH range of 1-7. Coexistence of xanthan gum and mucin at 1:2 ratio (w/w) under acidic pH results in phase separation, as evidenced by the formation of visible aggregates. zeta-Potential data rule out any relevant electrostatic interactions. Fluorimetry analysis points to the existence of two distant binding regimes of mucin, manifesting at low (y(1)) and high (y(2)) xanthan gum concentrations, corroborating a pH-independent two-step binding mechanism. Enthalpy-dominated (Delta H degrees < 0) interaction occur at pH 7, whilst, entropy-driven (Delta S degrees > 0) at the two pH values. Based on rheological data, the macromolecular interaction proves to be less dependent on the mucin to xanthan gum weight ratios. Nevertheless, the partial substitution of mucin with xanthan gum leads to enhanced viscoelasticity (G' > G `') and increased relaxation times (lambda). Furthermore, the xanthan gum inclusion in mucin systems at a 5:5 (w/w) ratio elevates the apparent viscosity (eta) >= 45-fold (21.59 Pa s) and >= 70-fold (33.52 Pa s) in comparison with mucin (0.46 - 0.48 Pa s) at pH 3 and pH 7, respectively. The findings of this study highlight the physicochemical basis of designing dysphagia diets, modulating food functionality, and tailoring the organoleptic properties of food systems.
Keywords
Oral processing, Mucin, Xanthan gum, Binding mechanism, Rheological synergism
Funders
College of Light Industry and Food, Nanjing Forestry University[163105084],Ministry of Science and Technology of China, The National Key Research and Development Plan[2017YFD0400101]
Publication Title
Food Hydrocolloids
Volume
114
Publisher
Elsevier Sci Ltd
Publisher Location
THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND