Molecular interactions and rheological characterization of binary biopolymer mixtures.

Our study provides predictive tools for formulating agri-food products with controlled rheological properties containing mixtures. We investigated the rheological properties of binary biopolymer mixtures composed of xanthan gum (XG) and carboxymethyl cellulose (CMC), with a focus on their synergistic interactions and applications in dysphagia management. Through steady and dynamic rheological tests, we characterized the flow behavior, viscoelastic properties, and thermal stability of XG/CMC blends at varying ratios (100/0 to 0/100). Principal outcomes reveal that XG-rich blends ( ≥ 70 % XG) exhibit pronounced elastic behavior ( G ' > G ' ' ), high yield stress, and strong shear-thinning properties, making them suitable for texture-modified foods requiring cohesive bolus formation. In particular, the apparent viscosity at γ ˙ = 50 s - 1 -a critical shear rate for swallowing-was found to be ∼ 350 mPa · s for pure XG ( 1 wt % ), classifying it as "honey-like" according to dysphagia standards. Blends with ≥ 70 % of XG maintained viscosities in the nectar-like to honey-like range (51- 1750 mPa · s ), while CMC-rich blends ( ≥ 60 % CMC) fell below 50 mPa · s ("thin"), rendering them unsuitable for dysphagia without reformulation. The Benhadid and Cross models effectively described the rheology of XG- and CMC-rich blends, respectively. Temperature studies highlighted XG's enhanced thermal stability (20- 30 % viscosity loss at 20- 60 ∘ C ) compared to CMC ( > 60 % loss above 30 ∘ C ). These results provide predictive tools for designing dysphagia-friendly formulations that balance rheological performance, safety, and sensory acceptability, with XG-dominant blends offering the most promising formulations for meeting IDDSI guidelines.