Some remarks on rheological properties of concentrated solutions of galactomannans

Rheological properties of concentrated solutions of galactomannans, locust bean gum (lb-gum) and guar gum (g-gum), were compared between samples from different manufacturers to examine the effects of prescreening for polysaccharides. The angular frequency dependence curves of the storage and loss moduli were similar in shape between lb-gum samples but were different quantitatively. This results in different values of the molecular weight between entanglements in the molten state (Me,melt) for the lb-gums, although Me,melt is a material constant. On the other hand, Me,melt for g-gum samples agreed with each other. It was demonstrated that the quantitative difference in the rheological properties of lb-gum solutions was attributed to the effective lb-gum concentration in the solutions and that Me,melt is surely a material constant even for these galactomannans. This study confirms that prescreening of samples is very important for polysaccharides to estimate Me,melt.