Impact of solutes and temperature on rheological and physical properties of particle gels from insoluble dietary fiber

The presence of different solutes, i.e., salts and sweeteners, and the adopted thermal condition during processing affects significantly rheological behavior of foods based on dietary fibers. In this work, the interactions between water and insoluble dietary fiber (IDF) from citrus and different solutes, such as sodium chloride (NaCl) calcium chloride (CaCl2), sucrose and low-calories sweeteners (erythritol, sorbitol) were investigated. A study on fiber hydration properties, such as water holding capacity (WHC) and water swelling capacity (WSC), was performed using the different aqueous systems and temperature. Then, the rheological properties of particle gels were studied. Microstructure was investigated with FTIR, Cryo-SEM and ζ-potential, aiming at understanding better the effects of solutes and their influence on macroscopic properties. Salt addition, owing to the shielding effects of cations on negative charges of fiber particles, yields the formation of larger and more compact clusters with a reduction in gel strength. As a consequence, at large salt concentrations, instability phenomena and phase separation occurred. The addition of sweeteners, on the other hand, affects hydrogen bonding by reducing the fiber hydration and, therefore, the gel strength yielding a less compact structure. This effect seems dependent on the molecular weight and on the OH functional group.