Insights into the nanostructure of low-methoxyl pectin–calcium gels

The nanostructure of calcium-low-methoxyl-pectin gels is still not fully understood despite its wide use in food and biomedical devices. In this study we present a comprehensive small angle X-ray scattering (SAXS) analysis of calcium–pectin gels with various calcium concentrations. Several modeling approaches were examined taking into account the contribution from both junction zones and chains between cross-links. The SAXS studies are supplemented by determination of the gels’ mechanical properties and swelling behavior. The model of semiflexible chains without excluded volume effects was found to be most suitable for describing calcium–pectin gels. The SAXS analysis suggests that both rod-like junction zones and point-like cross-links between neighboring chains are formed in calcium–pectin gels. Moreover, as the calcium content increases, the number of the rod-like junction zones decreases while the number of the point-like cross-links increases.