Microstructure and Rheological Behavior of Pure and Mixed Pectin Gels

Abstract

The microstructure and the rheological properties of pure HM (high methoxyl) and LM (low methoxyl) pectin gels and of mixed HM/LM pectin gels have been investigated. Gel formation of either the HM or LM pectin, or both, was initiated in the mixed gels by varying the sucrose and Ca(2+) content. The microstructure was characterized by transmission electron microscopy, light microscopy, and confocal laser scanning microscopy. HM and LM pectin gels showed aggregated networks with large pores around 500 nm and network strands of similar character. Small differences could be found, such as a more inhomogeneous LM pectin network with shorter and more branched strands of flexible appearance. LM pectin also formed a weak gel in 60% sucrose in the absence of calcium. A highly inhomogeneous mixed gel structure was formed in the presence of 60% sucrose and Ca(2+) ions, which showed large synergistic effects in rheological properties. Its formation was explained by the behavior of the corresponding pure gels. In the presence of 60% sucrose alone, a homogeneous, fine-stranded mixed network was formed, which showed weak synergistic effects. It is suggested that LM pectin interacts with HM pectin during gel formation, thereby hindering secondary aggregation leading to the aggregated networks observed for the pure gels.

Effects of Low-Methoxyl Pectin on Physicochemical and Sensory Properties of Reduced- Calorie Sorrel/ Roselle (Hibiscus sabdariffa L.) Jams

“…Hence, an increase in pectin would result in the removal of more H + ions from the solution. LM pectin gelation occurs in the presence of Ca 2+ ions, both with and without sugar [62]. The proposed mechanism is based on the described 'egg-box model' [63,64].…”

1H NMR and Rheological Studies of the Calcium Induced Gelation Process in Aqueous Low Methoxyl Pectin Solutions

“…The aggregated network of LM pectin gels with large pores of about 500 nm has been observed. Furthermore, the LM pectin gels have shown a more inhomogeneous structure, more flexible and branched network strands than purely HM pectin gels [20].…”

Removal of yttrium (III) ions from water solutions by alginate compounds

“…In the study with natural polysaccharides, pH of solution should be taken to account. This is an important parameter because the sorption system is strongly pHdependent due to the properties of both alginate compounds changing their charge and potential at different pH and the solution composition, i.e., metal ion speciation (Lofgren et al 2002;Schiewer and Patil 2008;Elliott et al 2013). The number of active binding sites presented with carboxyl group residues of the alginate molecule may also change due to varying pH.…”