Na+-induced gelation of a low-methoxyl pectin extracted from Premna microphylla Turcz

In this paper, Na+-induced gelation of a low-methoxyl pectin extracted from Premna microphylla Turcz were studied by rheological analysis, texture test, microstructure observation, thermodynamics study and gelling forces analysis. The results showed that Na+ could induce the gelation of ammonium oxalate extraction pectin from Premna microphylla Turcz (AOP) at room temperature. Besides, The Na+ concentration had a significant effect on the generation of AOP gel. There was an optimal Na+ concentration (0.6 M) for AOP to form a gel with the highest solid-like properties, water holding capacity (WHC) and crystallinity. With the further increase of Na+ concentration from 0.6 M to 0.7 M, the gel properties of the pectin gel would be weakened. Gelling forces analysis revealed that Na+-induced gelation of AOP was mainly caused by electrostatic shielding and hydrogen bonds. When sufficient content of Na+ was added to AOP, the electrostatic shielding effect of Na+ would reduce the expansion degree of AOP chains and make the pectin molecules get close to each other. Subsequently, hydrogen bonds in and between the pectin chains would be formed, thus building up the gel. The results of this study can provide references and methods for the mechanism study of monovalent cation-induced gelation of pectin.