Effect of xanthan gum co-extruded with OSA starch on its solubility and rheological properties

Xanthan gum (XG) was modified by the twin-screw extrusion process in the presence of Octenyl succinate anhydrate (OSA) starch in this study. The impact of OSA starch level on the rheological properties of XG was investigated. The extrusion process significantly improved the dispersibility, pseudoplasticity and elastic modulus of XG. The solubility and viscosity of the extruded XG in aqueous solution (1.0%, w/w) were increased from 67.04% and 0.2302 Pa⋅s to 95.20% and 1.1676 Pa⋅s, respectively, and reached the maximum of 96.63% and 1.7060 Pa⋅s when OSA starch level was 10%. Extruded samples were more sensitive to temperature and salt ion. Meanwhile, the co-extrusion process significantly changed the rheological properties of XG in the solutions at different pH values and sugar concentrations. The analysis of FTIR and SEM observation revealed that the molecular chains of XG and OSA starch were entangled through hydrogen bonding after the extrusion processing, leading to the formation of a denser network structure. In general, the extruded XG exhibited a strong gelatinous property with a high pseudoplasticity, while its features of high viscosity and dispersibility have a great potential for the application in food industry, especially in dysphagia products.