Effect of powder properties on the physicochemical and rheological characteristics of gelation inulin–water systems

Abstract

This study investigates the influence of physical properties of powder on the potential functionality of inulin as a polymeric gelator. Inulin powder was characterized using high-performance anion exchange chromatography, wide-angle X-ray, and particle size. Moreover, the inulin–water system was described using rheological properties, optical microscopy, and textural analysis. Four commercial inulins (LC, Instant, Fib97, and HP) were characterized and dissolved in distilled water at three different concentrations (15, 20, and 25%, w/w) at 25 °C. Inulin LC (degree of polymerization, 18.80; semi-crystalline state) and HP (degree of polymerization, 23.74; amorphous state) formed a gel from a concentration of 15% (w/w) and 20%, respectively. Inulin Fib97 (degree of polymerization, 6; amorphous state) and Instant (degree of polymerization, 8; amorphous state) were not able to develop a gel structure. This indicates the significant effect of polymer chain length to form a gel. Textural properties as well as wide-angle X-ray scattering and optical microscopy ascertained a difference in inulin HP– and LC–water system properties. This dissimilarity is related to the different physical properties of powders such as crystallinity and particle size. Indeed, new inulin powders were produced, having the same chemical composition but different physical states (amorphous or crystalline) or particle sizes. The results showed that an amorphous powder with a bigger particle size gave a greater gelation of inulin–water systems. However, beyond a certain size of particles, the systems lose their gelation properties.