RHEOLOGICAL PROPERTIES OF MIXTURES OF SPRUCE GALACTOGLUCOMANNANS AND KONJAC GLUCOMANNAN OR SOME OTHER POLYSACCHARIDES

Spruce galactoglucomannan is a wood-derived polysaccharide with a modest molar mass that has recently been made available in kg-scale for research and development of value-added products. To promote the application of spruce galactoglucomannans in, for example, food products, it is vital to understand also the rheological behaviour of the mixtures of galactoglucomannans with other polysaccharides. Rheological measurements were applied to study the rheological properties of mixtures of spruce galactoglucomannans and high-molar-mass konjac glucomannan, xanthan, guar gum, locust bean gum, and carrageenan. Shear rate-dependence of viscosity and applicability of the Cox-Merz relationship of mixtures of spruce galactoglucomannans with the other polysaccharides were studied. Spray-dried and ethanol-precipitated galactoglucomannans were also prepared for comparison. The effects of polysaccharide mixture ratio, temperature, ionic strength, and deacetylation are discussed. Mixtures of spray-dried galactogluco-mannans and konjac glucomannan showed lower elastic properties than those of ethanol precipitated galactoglucomannans and konjac glucomannan. The viscoelastic spectra of mixtures of both galactoglucomannans and deacetylated galactoglucomannans with konjac glucomannan showed temperature dependency throughout the cooling process. Ionic strength had an effect on the rheological properties of mixtures of galactoglucomannans with konjac glucomannan. Deacetylation of galactoglucomannans did not affect the viscoelastic spectra significantly.