Structure impact of two galactomannan fractions on their viscosity properties in dilute solution, unperturbed state...

Two fractions of carob galactomannans (GM25 and GM80) were extracted at respectively 25°C and 80°C from crude locust bean gum. Those fractions having slightly different chemical structures, previously characterized, were studied for their viscosity properties over a wide range of concentrations: diluted solution, unperturbed state and gel state. For each of the physical properties, links to the chemical fine structure could be established, expanding knowledge on the topic: in dilute solution, GM25 is more soluble in water while GM80 seems to tend to self-association due to its structure as highlighted by intrinsic viscosity measurements ([η]_GM25=9.96dLg^-1 and [η]_GM80=4.04dLg^-1). In unperturbed state, initial viscosities η₀ were more important for GM80 fractions at 1% and 2% due to greater hyperentanglements (η_0(GM80,1%)=9.9Pas; η_0(GM80,2%)=832.0; Pa.s η_0(GM25,1%)=3.1Pas; η_0(GM25,2%)=45.1Pas). In gel state, hydrogels obtained from GM80 were also stronger (hardness GM80 (2%)=0.51N and hardness GM25 (2%)=0.11N), suggesting a much more important number of junction areas within the gel network. The findings discussed herein demonstrate the potential for new applications.