A Molecular Description of the Gelation Mechanism of Konjac Mannan

A molecular level description of the time course of the gelation of the polysaccharide konjac mannan (KM) is presented and the role of alkali addition is considered in detail. NMR relaxometry is utilized as a complementary methodology to mechanical spectroscopy in order to probe events occurring as a prelude to network formation, and high-resolution NMR is used to follow the deactetylation process. It is shown that the addition of alkali plays an important solubilizing role in addition to facilitating the deacetylation of the chain. Deacetylation is important both in reducing the inherent aqueous solubility of the polymer and in progressively negating the alkali-induced polyelectrolytic nature of the polysaccharide chain via reaction induced pH changes. It is proposed that observed induction periods following alkali addition (during which the elastic modulus does not rise) are not simply deacetylation delays but are related to the aggregation kinetics of the deacetylated material.