Studies on macromolecular interactions in ternary mixtures of konjac glucomannan, xanthan gum and sodium alginate

Covalent and non-covalent macromolecular interactions were studied in the proprietary commercial product, PGX® (PolyGlycopleX®) which is manufactured from konjac glucomannan, xanthan gum and sodium alginate using a proprietary manufacturing process (EnviroSimplex®). Analytical techniques established the absence of changes in primary covalent structure of any of the component polysaccharides which may have occurred when the product was manufactured. However, non-covalent interactions between the polysaccharides were apparent in aqueous solutions of proprietary ternary mixtures by comparing their flow behaviour with those of unmixed controls. The interactions indicated by the flow behaviour confirmed those observed in the sedimentation behaviour, published earlier (Abdelhameed, A. S., Ang, S., Morris, G. A., Smith, I., Lawson, C., Gahler, R., et al. (2010). Carbohydrate Polymers, 81, 145–148). Non-covalent macromolecular interactions between konjac glucomannan and xanthan gum are already known in binary mixtures but the flow behaviour of solutions of laboratory-prepared ternary powder mixtures with variable sodium alginate content was consistent with a ternary macromolecular interaction involving sodium alginate at below 5% but this was significantly enhanced by heat treating the solutions when the sodium alginate content exceeded 5%. Sedimentation coefficient distribution analysis from analytical ultracentrifugation supports these observations showing a clear shift to higher sedimentation coefficients in the heat-treated solutions of ternary mixtures at sodium alginate concentrations >8%, and over a greater range compared with unheated material. Calcium ion addition failed to precipitate calcium alginate from solutions of PGX® (containing all three polysaccharides) but precipitates were obtained from solutions of binary mixtures prepared with either konjac glucomannan or xanthan gum plus sodium alginate. The results are consistent with an interaction between a konjac glucomannan–xanthan gum complex and sodium alginate to form a new, ternary complex.