NMR spectroscopy: A versatile tool for xanthan gum research

Xanthan gum (XG) is a microbial polysaccharide renowned for its unique and tunable rheological properties, yet correlating its complex molecular structure to functional performance remains challenging. This review highlights Nuclear Magnetic Resonance (NMR) spectroscopy as a versatile, multi-scale approach to bridge this gap, connecting XG's molecular architecture to its macroscopic behavior in solutions, hydrogels, and solid matrices. High-resolution NMR has been pivotal in defining XG's primary structure, including quantification of acetate and pyruvate substituents that govern the stability of its ordered helical conformation and gelation ability. Complementary solid-state NMR techniques elucidate XG's native conformation in gels and solids, chemical modifications, and the spatial distribution of functional groups along the polymer chain. Additionally, time-domain NMR provides quantitative insights into chain mobility and hydration dynamics correlated with rheological properties, while Magnetic Resonance Imaging (MRI) enables spatial mapping of component distribution in heterogeneous matrices. This review also identifies underexploited advanced techniques, such as those based on Nuclear Overhauser Effect (NOE), high-field relaxometry, and Diffusion-Ordered Spectroscopy (DOSY), which hold promise for resolving detailed molecular dynamics. Together, these insights establish a robust framework for the rational design and optimization of high-performance XG-based materials for diverse industrial and biomedical applications.