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 ( $\ge 70\%$ XG) exhibit pronounced elastic behavior ( $G^{\text{'}}>G^{\text{'}\text{'}}$ ), 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 $\dot{\gamma }=50s^{-1}$ -a critical shear rate for swallowing-was found to be $\sim 350\mathrm{mPa}·s$ for pure XG ( $1\text{wt}\%$ ), classifying it as "honey-like" according to dysphagia standards. Blends with $\ge 70\%$ of XG maintained viscosities in the nectar-like to honey-like range (51- $1750\mathrm{mPa}·s$ ), while CMC-rich blends ( $\ge 60\%$ CMC) fell below $50\mathrm{mPa}·s$ ("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- $60_{}^{\circ }\text{C}$ ) compared to CMC ( $>60\%$ loss above $30_{}^{\circ }\text{C}$ ). 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.